One Year After Study: A6 Clapham Bypass
One Year After Study: A6 Clapham Bypass
One Year After Study: A6 Clapham Bypass
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<strong>One</strong> <strong>Year</strong> <strong>After</strong> <strong>Study</strong>:<br />
<strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong><br />
March 2005
SFM/PIES 2000 COMMISSION<br />
ONE YEAR AFTER STUDY - <strong>A6</strong><br />
<strong>Clapham</strong> <strong>Bypass</strong><br />
JOB NUMBER: 4416516\600<br />
DOCUMENT REF: <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong> 1 Yr<br />
FINAL.doc<br />
01 Draft Report SG JM PR PR Nov 2004<br />
02 Incorporate HA and BCC<br />
comments and Executive<br />
Summary<br />
SG PW PR PR Mar 2005<br />
Originated Checked Reviewed Authorised Date<br />
Revision<br />
Purpose<br />
Description
SFM/PIES 2000 COMMISSION<br />
ONE YEAR AFTER STUDY - <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong><br />
Contents<br />
Section<br />
Executive Summary<br />
Page<br />
iii<br />
1. Introduction 1-1<br />
2. Data Collection and Evaluation 2-1<br />
Data Collection 2-1<br />
‘Before’ Surveys 2-1<br />
‘<strong>After</strong>’ Surveys 2-1<br />
Summary of Results 2-4<br />
Journey Times 2-6<br />
Journey Speeds 2-7<br />
Vehicle Classification 2-8<br />
3. POPE Methodology 3-1<br />
Introduction 3-1<br />
Vehicle Hour Benefits 3-1<br />
Changes in Journey Time 3-2<br />
Changes In Accident Benefits 3-4<br />
Summary of POPE Methodology 3-5<br />
4. Economic Benefits of the Two Schemes 4-1<br />
Introduction 4-1<br />
COBA Re-evaluation 4-1<br />
Re-Evaluation of Scheme Costs 4-3<br />
5. Evaluation Summary Table 5-1<br />
Introduction 5-1<br />
Appraisal Summary Tables (AST) 5-1<br />
Outturn Effects 5-4<br />
6. Summary of Conclusions 6-1<br />
List of Tables<br />
Table 2.1 - Journey Times along the <strong>A6</strong> between Bedford and Milton Ernest 2-7<br />
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Table 2.2 - Journey Times along the <strong>A6</strong> between Bedford and Milton Ernest 2-8<br />
Table 2.3 – Proportion of Traffic by Vehicle Type Using the Old <strong>A6</strong> 2-8<br />
Table 3.1 - Comparison of forecast and actual vehicle hours for <strong>Clapham</strong> along the bypass<br />
and bypassed links. 3-3<br />
Table 3.2 – Journey Time Benefits 3-3<br />
Table 3.3 - Comparison of POPE Outurn and Predicted Journey Time Benefits 3-3<br />
Table 3.4 – Comparison of actual and predicted number of accidents at <strong>Clapham</strong> along the<br />
bypass and bypassed links 3-4<br />
Table 3.5 – Accident Benefits 3-4<br />
Table 3.6 – Comparison of POPE Outturn and Predicted Accident Benefits 3-5<br />
Table 4.1 – Comparison of OPR AST and Revised COBA analysis 4-2<br />
Table 4.2 – Conversion of POPE Methodology Benefits for OPR AST Comparison 4-3<br />
Table 4.3 – Predicted and Outturn Scheme Costs 4-3<br />
Table 5.1 – AST for <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong> 5-3<br />
Table 5.2 – Summary of Accidents on the <strong>A6</strong> <strong>One</strong> <strong>Year</strong> Before 5-5<br />
Table 5.3 – Summary of Accidents on the old <strong>A6</strong> and <strong>Bypass</strong> <strong>One</strong> <strong>Year</strong> <strong>After</strong> 5-5<br />
Table 5.4 – Accident Severity Splits Before And <strong>After</strong> 5-5<br />
Table 5.5 – EST for <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong> 5-10<br />
List of Figures<br />
Figure 0.1 – Daily Traffic Flows ‘Before’ and ‘<strong>After</strong>’ Scheme Opening<br />
iii<br />
Figure 1.1 - <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong> Wider Area Context 1-1<br />
Figure 1.2 – <strong>A6</strong> <strong>Clapham</strong> bypass 1-2<br />
Figure 2.1 - Location of Traffic Count Sites 2-3<br />
Figure 2.2 - Journey Time Survey Routes 2-4<br />
Figure 2.3 - Traffic Volume Changes around <strong>Clapham</strong> 2-5<br />
Figure 5.1 – Accidents <strong>One</strong> <strong>Year</strong> Before the Opening of the <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong> 5-7<br />
Figure 5.2 – Accidents <strong>One</strong> <strong>Year</strong> <strong>After</strong> the Opening of the <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong> 5-8<br />
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Executive Summary<br />
The <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong> officially opened on 12 th December 2002, as illustrated in Figure<br />
0.1 below. The scheme consists of a 5 km long new section of dual carriageway road,<br />
diverging from the current <strong>A6</strong> on the northern outskirts of Bedford and rejoining the trunk<br />
road north of <strong>Clapham</strong> towards Milton Ernest. ‘Before’ and ‘<strong>After</strong>’ traffic data for the bypass<br />
was collected immediately prior to and one year after scheme opening. In addition, traffic<br />
data from surveys on County roads from Bedfordshire County Council and existing<br />
Highways Agency permanent count sites was obtained to evaluate the effects of the opening<br />
of the bypass on strategic traffic routing patterns in the area.<br />
Figure 0.1 – Daily Traffic Flows ‘Before’ and ‘<strong>After</strong>’ Scheme Opening<br />
The main effects of scheme opening are as follows:<br />
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<br />
Approximately 18,500 vehicles per day are using the <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong> one<br />
year after opening. Traffic volumes in the south of <strong>Clapham</strong> on the old <strong>A6</strong><br />
dropped from 23,000 to 8,500 vehicles per day (vpd) denoting a decrease of<br />
around 62% in traffic through <strong>Clapham</strong>. There has also been a reduction of<br />
vehicles on the old <strong>A6</strong> north of <strong>Clapham</strong> at Oakley Hill, where there has been a<br />
decrease from 14,500 vehicles per day to 1,700 vehicles per day, a decrease of<br />
88%. This decrease reflects the fact that this section of road between Highfield<br />
Road and the northern tie-in of the scheme is now southbound only, i.e. there is<br />
no northbound access to the <strong>A6</strong>, north of Oakley Road.<br />
Therefore the scheme has been successful in significantly reducing traffic<br />
volumes on the <strong>A6</strong> through <strong>Clapham</strong>.<br />
<br />
<br />
<br />
<br />
<br />
The scheme has also been successful in reducing journey times on the <strong>A6</strong> in<br />
that journey time savings of between 2 to 3 minutes are shown for most<br />
movements that previously used the <strong>A6</strong> through <strong>Clapham</strong>.<br />
In addition to the reduction in traffic along the old <strong>A6</strong> the proportion of HGV’s<br />
through <strong>Clapham</strong> dropped from 8% to 2% after the bypass opened.<br />
There has also been re-routing of traffic on the local roads in the area, for<br />
example;<br />
Traffic volume reductions of nearly 600 vehicles per day were recorded on<br />
Highfield Road between Oakley and north of <strong>Clapham</strong>, as traffic volumes fell<br />
from 5,200 vehicles per day to 4,600 suggesting a switch of traffic from<br />
villages such as Felmersham and Radwell who used to access the <strong>A6</strong> via<br />
Oakley Road / Highfield Road, but post opening of the new scheme, now<br />
access the <strong>A6</strong> at Milton Ernest.<br />
There are observed traffic volume increases of over 1,100 vehicles per day on<br />
Oakley Road, west of the <strong>Bypass</strong>, increasing from 6,200 vehicles per day to<br />
7,300 vehicles per day as a result of scheme opening, however there has<br />
been a corresponding decrease of 500 vehicles per day on Church Road<br />
which is road to Bromham suggesting that local journeys from Oakley to<br />
Bedford have re-routed to access the southbound <strong>Clapham</strong> <strong>Bypass</strong> rather<br />
than Church Road to Bromham and the A428.<br />
East of the <strong>Bypass</strong> on Oakley Road, traffic volumes fell by 1,700 vehicles per<br />
day as a result of scheme opening.<br />
The initial analysis accident data collated for the opening year indicates that the<br />
<strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong> has led to a reduction in the number of accidents in the<br />
corridor, where up to 7 personal injury accidents have been saved in the first<br />
year after opening.<br />
Comparison of the forecast benefits in the Appraisal Summary Table at the<br />
Order Publication Report stage with the outturn benefits of the scheme show that<br />
the prediction of the relief of traffic in <strong>Clapham</strong> was robust and that the accident<br />
savings predicted were also robust.<br />
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1. Introduction<br />
Background<br />
1.1 The <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong> officially opened on the 12 th December 2002. The scheme<br />
consists of a 5 km long new section of dual carriageway road, diverging from the<br />
current <strong>A6</strong> on the northern western outskirts of Bedford and rejoining the trunk road<br />
north of <strong>Clapham</strong> south of Milton Ernest. The <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong> has been named<br />
‘Paula Radcliffe Way’.<br />
1.2 The location of the improvements in the wider regional context is illustrated in Figure<br />
1.1. The scheme provides 2 interchanges from the bypass onto Oakley Road and<br />
Highfield Road.<br />
Figure 1.1 - <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong> Wider Area Context<br />
1.3 Figure 1.2 shows the completed scheme in more detail.<br />
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Figure 1.2 – <strong>A6</strong> <strong>Clapham</strong> bypass<br />
1.4 In order to assess the immediate responses to the new scheme, ‘Before’ and ‘<strong>After</strong>’<br />
traffic volume data on the <strong>A6</strong> and other competing routes was collected immediately<br />
prior to and after opening in December 2002 to monitor the effects of the new<br />
scheme.<br />
1.5 In addition, traffic data from surveys on County roads from Bedfordshire County<br />
Council and existing Highways Agency permanent count sites was obtained to<br />
evaluate the effects of the opening of the <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong> on strategic traffic<br />
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routeing patterns in the area and the effects of this immediate response to the<br />
improvements was reported in the Traffic Impact <strong>Study</strong> Report.<br />
Scheme Objectives<br />
1.6 The <strong>A6</strong> improvement is a scheme within the Highways Agency’s Road Programme<br />
called the Targeted Programme of Improvements (TPI). The scheme was<br />
implemented to address the following problems, which are listed within the scheme<br />
Appraisal Summary Tables (AST). These problems were:<br />
<br />
<br />
<br />
Noise and air quality problems in <strong>Clapham</strong>.<br />
Accidents due to pedestrian and vehicle conflict plus a poor standard single<br />
carriageway.<br />
Increased journey times due to having to travel through a built up area.<br />
Purpose of the Report<br />
1.7 This report represents the ‘<strong>One</strong>-<strong>Year</strong> <strong>After</strong>’ report for the <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong><br />
improvement scheme. This report has been prepared as part of the Post Opening<br />
Project Evaluation (POPE) Commission and builds on the Traffic Impact <strong>Study</strong> (TIS)<br />
report prepared for the Highways Agency in April 2003.<br />
1.8 This report will set out a number of assessments, namely:<br />
A comparison of the ‘Before’ and ‘<strong>After</strong>’ traffic volumes on the <strong>A6</strong> and other<br />
roads in the corridor and illustrate how traffic volumes have changed since the<br />
opening of the <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong>;<br />
A comparison of ‘Before’ and ‘<strong>After</strong>’ journey times on the <strong>A6</strong>;<br />
<br />
<br />
It will also present an evaluation of predicted and outturn economic forecasts<br />
based on changes in journey times as well as other outturn effects in the form of<br />
an Evaluation Summary Table (EST); and<br />
The report will also outline the changes in accidents on the route and whether<br />
they have changed since the opening of the <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong>.<br />
1.9 This report specifically considers the re-evaluation of the predicted benefits for the <strong>A6</strong><br />
<strong>Clapham</strong> <strong>Bypass</strong>. The three main elements involved are:<br />
<br />
<br />
<br />
To identify the costs and benefits originally forecast for the scheme at Order<br />
Publication Report (OPR) stage;<br />
To quantify the outturn (actual) costs and the outturn level of benefits actually<br />
accruing, based on outturn traffic volume and journey time data for the scheme;<br />
and<br />
To compare the results and quantify the difference in the Present Value of<br />
Benefits (PVB).<br />
1.10 Following this introduction the report has been divided into five further sections as<br />
follows:<br />
<br />
Section 2 outlines existing data collation and new data collection and reports on<br />
traffic volume and journey time changes attributable to the <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong>;<br />
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<br />
<br />
<br />
<br />
Section 3 presents an assessment of predicted and outturn economic benefits<br />
using the POPE journey time and accident reduction methodology;<br />
Section 4 presents the original economic results, calculated by the Department<br />
for Transport’s program COBA for these schemes and the level of benefits that<br />
would have been forecast if outturn traffic volumes and journey times were<br />
known at the time. The section also compares the COBA and POPE<br />
methodology;<br />
Section 5 presents the original Appraisal Summary Tables (AST) for the <strong>A6</strong><br />
<strong>Clapham</strong> <strong>Bypass</strong> and then re-evaluates these predictions within an Evaluation<br />
Summary Table (EST). The section also gives an early indication of changes in<br />
the number of accidents in the corridor;<br />
Section 6 summarises the main conclusions from the evaluations and the<br />
limitations to use.<br />
1.11 It should be noted, that the ‘<strong>One</strong>-<strong>Year</strong> <strong>After</strong>’ report is primarily focused on the<br />
evaluation of Economy and Safety sub-objectives of the GOMMMS Appraisal.<br />
Environmental evaluation has not been carried out at this stage, but will form part of<br />
the ‘5-<strong>Year</strong> <strong>After</strong>’ evaluation.<br />
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2. Data Collection and Evaluation<br />
DATA COLLECTION<br />
2.1 This <strong>One</strong> <strong>Year</strong> ‘<strong>After</strong>’ Report for the <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong> includes the following<br />
surveys:<br />
‘BEFORE’ SURVEYS<br />
3 Highways Agency Automatic Traffic Count (ATC) surveys on the <strong>A6</strong>;<br />
<br />
<br />
<br />
4 ATC surveys by Bedfordshire County Council;<br />
Journey time surveys undertaken in April 2002 on the existing <strong>A6</strong> route and<br />
adjoining roads. Journey time surveys were undertaken at this time to ensure<br />
normal operating conditions.<br />
Turning count data for the <strong>A6</strong> at the junctions for Oakley Road and Highfield<br />
Road.<br />
‘AFTER’ SURVEYS<br />
2.2 Due to the de-trunking of the <strong>A6</strong> in the period between the Traffic Impact <strong>Study</strong> and<br />
the <strong>One</strong> <strong>Year</strong> <strong>After</strong> Report, the responsibilities for the count sites had altered and the<br />
Highways Agency ATC sites were no longer operational. In circumstances where<br />
data was no longer readily available from the sources used for the ‘Before’ or TIS<br />
surveys, alternative means were used to provide re-assessment at the same<br />
locations used for the ‘Before’ study and the TIS. The survey programme can be<br />
summarised as:<br />
<br />
<br />
<br />
<br />
<br />
2 former Highways Agency ATC sites on the <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong> and <strong>A6</strong><br />
Bedford Road, Knotting were re-fitted with counters by Northern Link Traffic Data<br />
Consultancy in June;<br />
2 temporary ATC count sites were placed on the old <strong>A6</strong> between 10 th May and<br />
24 th May, one at a former HA permanent ATC site by Northern Link Traffic Data<br />
Consultancy ;<br />
3 Bedfordshire temporary ATC site locations around Oakley plus one permanent<br />
site on the <strong>A6</strong> South of Milton Ernest which BCC monitors annually in Spring;<br />
Journey time surveys. Consistent with the additional journey time survey on the<br />
<strong>Bypass</strong> conducted for the TIS, this survey was reassessed for the <strong>One</strong> <strong>Year</strong><br />
‘<strong>After</strong>’ Report; and<br />
12 hour turning count data for 6 junctions conducted by Count on Us on the 12 th<br />
May.<br />
2.3 The details of the ‘Before’ and ‘<strong>After</strong>’ surveys (with OSGR’s for site locations) are<br />
described below.<br />
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Automatic Traffic Counts<br />
2.4 Atkins undertook automatic traffic count (ATC) surveys in May and June 2004 at the<br />
following sites (Counts are volumetric unless stated otherwise):<br />
<br />
<br />
<br />
<br />
<strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong> between Northbound Slip and Oakley Road Interchange;<br />
<strong>A6</strong> Bedford Road, Knotting - Classified count, vehicles greater than 5.2metres;<br />
Old <strong>A6</strong> <strong>Clapham</strong>, South of Green Lane on road sign; and<br />
Old <strong>A6</strong> <strong>Clapham</strong>, North of Oakley Road on road sign.<br />
2.5 In order to ascertain the effects of the <strong>Bypass</strong> on the roads in the Oakley area,<br />
Bedfordshire County Council undertook counts at three ATC on the adjoining roads<br />
and provided data from counts between Milton Ernest and the bypass in May as part<br />
of their annual monitoring. The locations of these counts are listed below.<br />
Highfield Road on the West side of the bypass (501360,254075);<br />
Church Lane (500580,252800);<br />
Oakley Road on the West side of the bypass (502000,252925); and<br />
<strong>A6</strong> between Milton Ernest and <strong>Bypass</strong> (501930,254810).<br />
2.6 Classified turning counts were also conducted at six junctions. Vehicles were divided<br />
into Cars, Light Vehicles, Heavy Goods Vehicles 1, Heavy Goods Vehicles 2 and<br />
Passenger Service Vehicles. The locations of the six sites are detailed below.<br />
<br />
<br />
<br />
<br />
<br />
<br />
Highfield Road/ Milton Road/ <strong>A6</strong> South off-slip;<br />
Highfield Road/ <strong>A6</strong> South on slip;<br />
Highfield Road/ <strong>A6</strong> North on-off slip;<br />
Milton Road/Oakley Road;<br />
Oakley Road/ <strong>A6</strong> South on-off slip; and<br />
Oakley Road/ <strong>A6</strong> North on-off slip.<br />
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Journey Time Surveys<br />
Figure 2.1 - Location of Traffic Count Sites<br />
2.7 Four journey time surveys were undertaken on four routes, identified as ‘blue’, ‘pink’,<br />
‘orange’ and ‘green’ routes, which are illustrated in Figure 2.2 with the respective<br />
timing points used for each route. The ‘blue’ route represented the old <strong>A6</strong> between<br />
Milton Ernest and the <strong>A6</strong> <strong>Clapham</strong> Road / Shakespeare Road roundabout south of<br />
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<strong>Clapham</strong>, whereas the ‘green’ route was an ‘after’ survey only on the new bypass<br />
between the same two points. The ‘pink’ and ‘orange’ routes were used to derive<br />
estimates of journey time change form Oakley to the <strong>A6</strong> on Highfield Road and<br />
Oakley Road respectively.<br />
2.8 ‘Before’ journey time surveys previously undertaken on Tuesday 24 th April 2002 were<br />
used for comparison with the <strong>One</strong> <strong>Year</strong> <strong>After</strong> surveys undertaken between Monday<br />
17 tth and Wednesday 19 th May 2004. Survey periods were the morning (07:30 –<br />
09:00) and evening (16:30 - 18:00) peaks, and an inter-peak period (10:00 -11:30).<br />
Figure 2.2 - Journey Time Survey Routes<br />
SUMMARY OF RESULTS<br />
Traffic Volume Changes<br />
2.9 Figure 2.3 below shows the changes in daily traffic volumes on the <strong>A6</strong> and other<br />
roads in the area. The ‘Before’ and ‘TIS <strong>After</strong>’ counts have been adjusted up to<br />
reflect May 2004 traffic levels to ensure the conclusions drawn take into account<br />
seasonality and normal traffic growth. This has been done by using the seasonally<br />
adjusted traffic growth index 1 to determine normal background growth between the<br />
1 Department for Transport (2004) ‘Traffic in Great Britain, Q2 2004’<br />
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count data and an index to adjust the average daily traffic flow based upon monthly<br />
seasonal variations in traffic flow. 2<br />
Figure 2.3 - Traffic Volume Changes around <strong>Clapham</strong><br />
2.10 The main points to note for traffic volume changes on the <strong>A6</strong> around <strong>Clapham</strong> are:<br />
2 Department for Transport (2004) ‘Road Traffic Statistics : 2003’<br />
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<br />
<br />
The traffic volume data collected as part of this study demonstrates that the <strong>A6</strong><br />
through <strong>Clapham</strong> carried approximately 15,000 to 23,000 vehicles per day (vpd)<br />
before the opening of the bypass. <strong>One</strong> year after opening, this has dropped to<br />
approximately between 2,000 to 8,500 vehicles per day clearly indicating that<br />
the scheme has been successful in routeing vehicles away from the<br />
village;<br />
A year after opening the traffic on the bypass has risen to around 18,500 vpd<br />
from about 17,000 vpd, an increase of around 9%.<br />
This level of growth is above the normal increase in traffic flow, and thus it<br />
seems likely that the <strong>A6</strong> scheme has drawn some additional traffic into the<br />
corridor in the form of new trips and re-assigned traffic.<br />
At the time of Traffic Impact <strong>Study</strong> local traffic had been reduced by 1,500<br />
vehicles per day on Highfield Road which was likely to be due to re-routing of<br />
trips from wider areas in the Northwest such as Odell and Felmersham joining<br />
the <strong>A6</strong> <strong>Bypass</strong> at Milton Ernest where previously they would have joined the <strong>A6</strong><br />
at <strong>Clapham</strong>. Although traffic flows along Highfield Road have increased slightly<br />
the since the TIS, flows on this road are still 11% lower than before the bypass<br />
opened.<br />
<br />
There is no evidence of the bypass resulting in a diversion of traffic from the<br />
Bromham area through Oakley to join the <strong>Bypass</strong> with traffic levels through<br />
Church Lane, which is the corridor linking Bromham and Oakley experiencing a<br />
slight decrease from 7,900 vpd before opening to 7,400 one year after.<br />
JOURNEY TIMES<br />
2.11 Journey time surveys were undertaken on the key corridors between Bedford and<br />
Milton Ernest and between Oakley and <strong>Clapham</strong> which would benefit from the<br />
<strong>Bypass</strong>.<br />
2.12 The surveys covered the full <strong>A6</strong> <strong>Bypass</strong> from the Bedford Roundabout up to Milton<br />
Ernest and the same start and finish points but using the old <strong>A6</strong> instead. Journey<br />
times were also surveyed from the old <strong>A6</strong> to Oakley via Highfield Road and Oakley<br />
Road respectively. Survey periods were the morning (07:30 – 09:00) and evening<br />
(16:30 - 18:00) peaks as well as an inter-peak period (10:00 -11:30).<br />
2.13 The ‘before’ and ‘after’ survey periods were December 2002 and May 2004<br />
respectively, and thus the time savings shown reflect the completion of the <strong>A6</strong><br />
<strong>Clapham</strong> <strong>Bypass</strong>.<br />
2.14 The journey time survey results are shown in Table 2.1 below. For the <strong>One</strong> <strong>Year</strong><br />
<strong>After</strong> <strong>Study</strong>, a further analysis of the before data indicated some delay impacts<br />
attributable to the bypass construction affecting the before data used in the TIS and<br />
these delays have been removed from the journey times. Therefore the ‘Before’<br />
figures used in the <strong>One</strong> <strong>Year</strong> <strong>After</strong> <strong>Study</strong> do not reflect what was used in the TIS.<br />
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ONE YEAR AFTER STUDY - <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong><br />
Journey Time (Minutes)<br />
Direction Period Before<br />
(April 02)<br />
<strong>After</strong><br />
(December<br />
02)<br />
1 <strong>Year</strong> <strong>After</strong><br />
(May/June<br />
04)<br />
Saving<br />
(Before and<br />
1 <strong>Year</strong><br />
<strong>After</strong>)<br />
Northbound<br />
AM Peak 07:24 05:22 04:30 02:54<br />
Inter Peak 07:12 05:13 04:35 02:37<br />
PM Peak 07:16 05:14 04:46 02:30<br />
Southbound<br />
AM Peak 07:10 04:59 07:47 -00:37<br />
Inter Peak 07:51 05:01 04:28 03:23<br />
PM Peak 06:59 04:55 04:54 02:05<br />
Table 2.1 - Journey Times along the <strong>A6</strong> between Bedford and Milton Ernest<br />
2.15 From the Journey Time data it suggests that vehicles travelling Northbound are<br />
saving approximately two and a half minutes per journey all day which is an increase<br />
on the TIS saving of about 30 seconds to a minute. This saving is also evident<br />
southbound with the exception of in the AM peak where there is indication of an<br />
increase in journey time.<br />
2.16 Further examination of this increased journey time southbound in the AM Peak<br />
indicates that heavy congestion is occurring in the area by the new roundabout at the<br />
southern end of the bypass at about 8:30 which is increasing journey times<br />
significantly and increasing the average AM peak journey time which is generally<br />
between 4 and 5 minutes before 8:30. This congestion is also evident on the old <strong>A6</strong><br />
journey time surveys around the same time period and the congestion was<br />
experienced on two different days indicating that the congestion is likely to be due to<br />
the traffic volumes approaching Bedford at that time as opposed to any unusual<br />
occurrences affecting the surveys.<br />
2.17 It should also be noted that in conjunction with the bypass a new 50 mph zone<br />
complete with safety cameras operated by Bedfordshire and Luton Safety Camera<br />
Partnership was established on the <strong>A6</strong> between Milton Ernest and the northern end<br />
of the bypass. This will impact the journey time surveys on the timing points on this<br />
section for the <strong>One</strong> <strong>Year</strong> <strong>After</strong> Surveys.<br />
JOURNEY SPEEDS<br />
2.18 Based upon the information compiled for the journey time surveys, Table 2.2<br />
compares the Journey Speeds ‘Before’, ‘<strong>After</strong>’ and ‘<strong>One</strong> <strong>Year</strong> <strong>After</strong>’ scheme opening.<br />
Average speeds on the new <strong>A6</strong> bypass are between 11kph and 26kph faster<br />
depending on direction of travel and time of day.<br />
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ONE YEAR AFTER STUDY - <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong><br />
Journey Speed (Minutes)<br />
Direction Period Before<br />
(April 02)<br />
<strong>After</strong><br />
(December<br />
02)<br />
1 <strong>Year</strong> <strong>After</strong><br />
(May/June<br />
04)<br />
Saving<br />
(Before and<br />
1 <strong>Year</strong><br />
<strong>After</strong>)<br />
Northbound<br />
AM Peak 62 69 82 20<br />
Inter Peak 63 71 81 18<br />
PM Peak 63 71 78 15<br />
Southbound<br />
AM Peak 64 75 64 0<br />
Inter Peak 58 74 84 26<br />
PM Peak 65 76 76 11<br />
Table 2.2 - Journey Speeds along the <strong>A6</strong> between Bedford and Milton Ernest<br />
VEHICLE CLASSIFICATION<br />
2.19 The manual turning counts provided classified data in addition to volumetric counts.<br />
Turning counts were conducted for the ‘Before’ <strong>Study</strong> at the junction between the <strong>A6</strong><br />
and Oakley Road, and the roundabout between the <strong>A6</strong> and Highfield Road. These<br />
counts were repeated for the <strong>One</strong> <strong>Year</strong> ‘<strong>After</strong>’ <strong>Study</strong> in addition to turning counts at<br />
the slip roads on the <strong>Bypass</strong>.<br />
2.20 Classification of vehicles was Cars, Light Goods Vehicles (LGV’s), Heavy Goods<br />
Vehicles (HGV’s) and Public Service Vehicles (PSV’s). In addition to determining the<br />
actual changes in traffic flows through the village, the classified counts provide<br />
information about the effect the bypass has had on individual vehicle types.<br />
2.21 In addition to the reduction in traffic along the old <strong>A6</strong>, Table 2.3 shows that between<br />
the hours of 7:00 to 19:00, the proportion of HGV’s as total traffic through <strong>Clapham</strong><br />
dropped from 8% to 2% after the bypass opened. The Manual Classified Count<br />
conducted at Milton Ernest indicates that HGV’s still comprises of approximately 7%<br />
of traffic along the corridor and that the bypass has clearly been successful in rerouting<br />
HGV’s out of <strong>Clapham</strong>, and onto the bypass.<br />
Car<br />
LGV<br />
HGV<br />
OGV<br />
Vehicle Type Before <strong>Study</strong> <strong>After</strong> <strong>Study</strong> Change<br />
80% 86% 6%<br />
11% 10% -1%<br />
8% 2% -6%<br />
1% 2% 1%<br />
Table 2.3 – Proportion of Traffic by Vehicle Type Using the Old <strong>A6</strong><br />
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3. POPE Methodology<br />
INTRODUCTION<br />
3.1 As part of this <strong>One</strong>-<strong>Year</strong> <strong>After</strong> <strong>Study</strong>, the Report is also assessing the predicted level<br />
of economic benefits. This section assesses the level of economic benefits predicted<br />
for the <strong>A6</strong> <strong>Clapham</strong> bypass and compares these predictions with actual benefits<br />
accrued when considering actual traffic volume changes and actual journey time<br />
benefits.<br />
3.2 The approach that we have taken is termed the Post Opening Project Evaluation<br />
(POPE) methodology. The basis of the POPE methodology is that through previous<br />
COBA evaluations undertaken it has been identified that the majority of benefits are<br />
derived primarily from two areas:<br />
<br />
<br />
Link Transit time (vehicle hours) benefits; and<br />
Accident Benefits.<br />
3.3 As such, link transit time, (which is represented by traffic volumes multiplied by<br />
journey times) and the number of accidents can be collected before and after<br />
scheme opening and the difference between these observed values can be<br />
compared to the difference shown in time and accidents for the same links shown in<br />
the OPR COBA’s. The premise of the POPE methodology is that the change in the<br />
observed flows, times and accidents can be directly associated to the economic<br />
benefits predicted for this scheme.<br />
3.4 The following section outlines this approach in more detail.<br />
VEHICLE HOUR BENEFITS<br />
3.5 To calculate link transit time or vehicle hour benefits, the COBA deck from OPR must<br />
be available, and the following changes implemented so that sensible and like-for-like<br />
comparisons can be made:<br />
<br />
<br />
<br />
<br />
OPR - Do Minimum: Although flow and delay data was probably collected prior<br />
to scheme implementation at the OPR stage, journey time and delay information<br />
must be determined by re-running the COBA deck with a journey time year set to<br />
the same as that when the Post Opening surveys were undertaken;<br />
OPR - Do Something: As with the OPR Do Minimum this data will need to be<br />
determined from re-running the COBA deck for the survey year after opening;<br />
Actual - Do Minimum: Pre opening count and journey time data is collected for<br />
each new scheme route before opening. This information is obtained for the AM,<br />
IP and PM time periods; and<br />
Actual - Do Something: Traffic volumes and journey times from surveys after<br />
the opening of the schemes are directly applicable to this scenario.<br />
3.6 The original Appraisal Summary Table published was in July 1998 and subsequently<br />
a revised COBA was produced in 2001. The benefits of the revised version differ<br />
from what was originally published in the AST and it is the revised COBA that has<br />
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been used in the POPE analysis for this scheme which has been adapted to enable<br />
comparison between the original OPR AST and the POPE methodology. Both the<br />
differences between the benefits and the methodology used for the revised COBA<br />
benefits will be explained in detail in Chapter 5. All monetary benefits are in 1998<br />
resource prices discounted to 1998.<br />
3.7 In considering the changes between the COBA forecast benefits and the observed<br />
vehicle hour benefits, there are limitations bought about by the availability of data.<br />
Only peak hour and off peak hour journey times are available for the key links before<br />
and after opening, even though count data has been collated for the whole 24 hour<br />
period.<br />
3.8 This means that only the bypass and bypassed links (where data is available) are<br />
considered in the POPE assessment, and thus the change in vehicle hours can be<br />
compared with the change in link transit time for the same links in the OPR COBA.<br />
3.9 This test assumes that flow data, on key links, is available by hour for a 24 hour<br />
period and journey time data is only available for the peak and off peaks. This<br />
enables the proportion of total traffic travelling in the AM peak, PM peak and Off<br />
Peak and the application of the peak and off peak journey time to these proportions.<br />
3.10 For the COBA OPR expansion factors from peak hour to peak period and off peak<br />
period to all other hours have been calculated from the Do Minimum observed flow<br />
data. This has then been used to factor up the outturn data to a total average day.<br />
CHANGES IN JOURNEY TIME<br />
3.11 In conducting the analysis of link transit time the one year after traffic flows have<br />
been adjusted to remove any traffic growth due to induced traffic as a result of<br />
opening of the bypass because the flows indicate that there has been additional<br />
traffic growth on this corridor above the level of national growth. This suggests that<br />
the additional flows may have come from people who previously did not use the <strong>A6</strong><br />
using the new bypass as it will reduce their overall journey time. As it is not possible<br />
to determine the journey time saving of these newly generated trips along the bypass<br />
the analysis focuses primarily on the savings related to flows removed from the old<br />
<strong>A6</strong> onto the bypass. The assumption used do this was that all induced traffic along<br />
this corridor would be on the bypass and therefore in the after scenario, the flows on<br />
the bypass could be split into trips transferred from the old <strong>A6</strong> and new trips along<br />
the corridor.<br />
3.12 The journey time data also enabled the additional savings of bypass users originating<br />
along Highfield Road and Oakley Road to be estimated as the bypass is located<br />
nearer to Oakley than the old <strong>A6</strong> and therefore they will experience subsequent<br />
decreases in journey time equal to the journey time between the bypass slip road<br />
and the two roads respective junctions with the old <strong>A6</strong>.<br />
3.13 Table 3.1 shows the differences between the vehicle hours before and after opening<br />
of the bypasses (observed traffic volumes multiplied by journey times) and the<br />
differences between flow multiplied by the forecast journey times for the same links in<br />
the COBA OPR.<br />
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SFM/PIES 2000 COMMISSION<br />
ONE YEAR AFTER STUDY - <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong><br />
Low Growth<br />
High Growth<br />
OPR COBA<br />
Do Minimum 466,027 562,214<br />
Do Something 317,868 354,408<br />
Difference 148,159 207,806<br />
Observed<br />
‘Before’ 622,423 622,423<br />
‘<strong>After</strong>’ 440,409 440,409<br />
Difference 182,013 182,013<br />
Table 3.1 - Comparison of forecast and actual vehicle hours for <strong>Clapham</strong> along the<br />
bypass and bypassed links.<br />
3.14 Table 3.1 shows that the saving in observed vehicle hours for the <strong>Clapham</strong> bypass is<br />
182,000 hours over the year. For the same links and scheme year, the Low Growth<br />
prediction was 148,000 and the High Growth prediction was 208,000. The COBA<br />
assessment showed that the Link Transit Time benefits for this scheme was £27.85m<br />
for the Low Growth Scenario and £40.92m for the High Growth Scenario.<br />
3.15 It was normal at the time of the OPR assessment for Low and High Growth to be<br />
weighted to create an average cost, by utilising 60% of the Low Growth result, and<br />
40% of the High Growth Result. We have retained this assumption when considering<br />
weighted growth in this report. Using the relationship between vehicle hours saved<br />
and economic benefit from the COBA analysis, the observed 182,000 hours saved<br />
correlates to £35.0m benefits. Table 3.2 compares the forecast and actual journey<br />
time benefits for the scheme.<br />
COBA Forecasts<br />
Actual<br />
Difference in<br />
Annual Vehicle<br />
Hours in 2003<br />
30 <strong>Year</strong><br />
Journey Time<br />
Benefits<br />
Difference in<br />
Annual Vehicle<br />
Hours in 2003<br />
30 <strong>Year</strong><br />
Journey Time<br />
Benefits<br />
Low Growth 148,159 £27.85m 182,013 £35.00m<br />
High Growth 207,806 £40.92m 182,013 £35.00m<br />
Table 3.2 – Journey Time Benefits<br />
3.16 The POPE comparison suggests that the forecast journey time benefits for the<br />
scheme is £33.1m compared with actual outturn benefits of £35.0m as shown in<br />
Table 3.3 -. The outturn journey time benefits are estimated to be approximately 6%<br />
higher than predicted.<br />
Predicted Benefits POPE Outturn Benefits Percentage difference<br />
£33.08m £35.00m 5.8%<br />
Table 3.3 - Comparison of POPE Outurn and Predicted Journey Time Benefits<br />
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3.17 Two potential caveats exist with the journey time saving analysis using the POPE<br />
methodology and should be considered when interpreting these results.<br />
<br />
<br />
The POPE analysis does not consider any journey time savings for the new trips<br />
or reassigned trips which are drawn into the corridor.<br />
The impacts of the bypass on the section between the newly constructed south<br />
roundabout and the Manton Lane roundabout section have not been evaluated<br />
as no counts were made on this section. The indication from the <strong>One</strong> <strong>Year</strong> <strong>After</strong><br />
<strong>Study</strong> is that congestion is occurring on this stretch of road which is the key route<br />
into Bedford from the <strong>A6</strong> and also has the entrance to Sainsburys supermarket.<br />
Some of this congestion is likely to be due to the induced traffic generated by the<br />
bypass which has subsequently has caused negative journey time impacts on<br />
flows on this section and these increased journey times have not been included<br />
in the POPE analysis.<br />
CHANGES IN ACCIDENT BENEFITS<br />
3.18 Table 3.4 below shows the difference between the actual number of accidents before<br />
and after opening of the bypass and the difference between the numbers of<br />
accidents predicted by COBA. The observed ‘Before’ accidents are based on<br />
average annual accident rates for the 3 years before the scheme opening.<br />
OPR COBA<br />
Observed<br />
Low Growth High Growth<br />
Do Minimum 9.3 11.3<br />
Do Something 3.4 4.2<br />
Difference 5.8 7.1<br />
‘Before’ 13.0 13.0<br />
‘<strong>After</strong>’ 6.0 6.0<br />
Difference 7.0 7.0<br />
Table 3.4 – Comparison of actual and predicted number of accidents at <strong>Clapham</strong><br />
along the bypass and bypassed links<br />
3.19 The COBA assessment showed that accident benefits were £9.54m for the 30 <strong>Year</strong><br />
Appraisal period. This means that 7 accidents saved in 2003 correlates to £9.54m of<br />
accident benefits over the 30 year appraisal period. Table 3.5 shows the POPE<br />
estimates of accident benefits for High and Low growth.<br />
COBA Forecasts<br />
Actual<br />
Difference in<br />
number of<br />
accidents in<br />
2003<br />
30 <strong>Year</strong><br />
Journey Time<br />
Benefits<br />
Difference in<br />
number of<br />
accidents in<br />
2003<br />
30 <strong>Year</strong><br />
Journey Time<br />
Benefits<br />
Low Growth 5.8 £9.29m 7.0 £11.09m<br />
High Growth 7.1 £11.14m 7.0 £11.09m<br />
Table 3.5 – Accident Benefits<br />
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ONE YEAR AFTER STUDY - <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong><br />
3.20 Table 3.6 summarises the comparison of outturn and predicted accident benefits for<br />
the weighted growth. This shows that outturn accident benefits on the bypass and<br />
bypassed links were about 11% higher than forecast.<br />
Predicted Benefits POPE Outturn Benefits Percentage difference<br />
£10.03m £11.09m 10.6%<br />
Table 3.6 – Comparison of POPE Outturn and Predicted Accident Benefits<br />
SUMMARY OF POPE METHODOLOGY<br />
3.21 These results suggest that the POPE methodology may be a robust way of<br />
evaluating link transit time benefits, particularly when most of the key links have all<br />
been counted and journey times have been undertaken.<br />
3.22 The POPE methodology for accidents should be treated with caution, as it is normal<br />
for changes in accidents to be assessed over 3-5 years. Therefore, conclusions can<br />
only be considered as indicative when they are derived from only one year’s data.<br />
3.23 Thus, the POPE methodology will continue to be used on other schemes in order to<br />
provide a larger sample to verify POPE as an evaluation tool.<br />
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4. Economic Benefits of the Two Schemes<br />
INTRODUCTION<br />
4.1 Economic benefits of a scheme have been traditionally assessed using the<br />
Government’s COBA (Cost Benefit Analysis) program, which considers changes in:<br />
<br />
<br />
<br />
Link transit time, which is the time on each affected link both before and after<br />
opening weighted by vehicle flows;<br />
Vehicle operating costs (VOC), reflecting fuel and other operating costs<br />
calculated by a change in total distance travelled on the affected links, but also<br />
considering vehicle speeds; and<br />
Accident rates and costs, which change after infrastructure improvements are<br />
made as accidents are normally less frequent on new roads.<br />
4.2 This section presents a comparison of predicted benefits as calculated by COBA and<br />
an assessment of what those benefits would be if the outturn traffic volumes and<br />
journey time savings were known at the time.<br />
COBA RE-EVALUATION<br />
4.3 The original Order under the Highways Act 1980 for the <strong>A6</strong> <strong>Clapham</strong> bypass was<br />
made in 1992. The Appraisal Summary Table published for this scheme was for a<br />
1996 scheme (Version of 22 July 1998) and reflects the benefits put forward for<br />
public inquiry and the OPR.<br />
4.4 The relevant COBA data for the scheme published in the AST was unavailable but a<br />
revised COBA was produced by the DETR in November 2001. Although these were<br />
not the exact figures which the OPR would have been based, due to the time elapsed<br />
between the OPR and the construction of the bypass this revised COBA will be<br />
based on more accurate scheme specification and more recent economic and traffic<br />
growth forecasts over the 30 year appraisal period of the project. Therefore the<br />
revised COBA will more accurately reflect the benefits of the scheme and has been<br />
used for the purpose of this evaluation.<br />
4.5 To provide a re-evaluation of scheme benefits, the objective would be to introduce<br />
actual traffic volumes, rather than predicted traffic volumes, whereby the outturn<br />
traffic volumes are also input into the Do Minimum scenario. Although the benefits in<br />
the original COBA run and generally matched closely with the results in the POPE<br />
methodology, upon closer examination of the COBA network and forecast flows it<br />
was not possible to replicate this using the observed data primarily due to the way<br />
the input flows had been modelled and the fact that the COBA network used<br />
consisted of 200 links and therefore based upon the limited journey time and traffic<br />
flow data, accurately updating the network would not feasible.<br />
4.6 To enable a consistent comparison with the AST, the differing scheme opening years<br />
between the AST and the revised COBA need to be adjusted as the AST was based<br />
upon the scheme discounted back to 1994 and the revised COBA was based upon a<br />
the scheme discounted back to 1998.<br />
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4.7 To enable a consistent comparison, the revised COBA was discounted back a further<br />
4 years to 1994. This would effectively lower the outturn benefits because the first<br />
year of benefits would be realised further in the future from the discounting base<br />
resulting in the first year of benefits being lower solely due to the benefits stream<br />
being further in the future.<br />
4.8 This process replicates the benefits from the COBA revision with the 2003 opening<br />
date and puts it in the context of the OPR AST enabling a direct comparison to be<br />
made between the revised COBA and the original OPR. Based on this adjustment,<br />
Table 4.1 shows the difference between the revised COBA and the original OPR<br />
publication.<br />
Benefit AST OPR (1994<br />
prices discounted<br />
to 1994)<br />
Revised COBA<br />
(1998 prices<br />
discounted to<br />
1998)<br />
Revised COBA<br />
(1994 prices<br />
discounted to<br />
1994)<br />
Journey Time and<br />
Vehicle Operating<br />
Cost<br />
£27.6m £34.56m £30.95m<br />
Accident Benefits £10.5m £10.30m £9.22m<br />
PVB £38.2m £44.86m £40.17m<br />
Table 4.1 – Comparison of OPR AST and Revised COBA analysis<br />
4.9 The revised COBA which was produced in 2001 for a 2003 opening when adjusted<br />
for a 1994 price and discounting base, estimated journey time savings to be 12%<br />
higher than in the original OPR AST and the accident savings to be 12% lower. The<br />
overall effect is a Present Value of Benefits (PVB) 5% higher than when the original<br />
OPR AST was produced.<br />
4.10 For the purpose of the comparison of the Appraisal Summary Table and Evaluation<br />
Summary Table in Chapter 5, it will also be necessary to convert the results from the<br />
POPE methodology using the same process. Vehicle operating costs have not been<br />
considered in the POPE evaluation as they are expected to be negligible and only<br />
account for 1% of PVB in the COBA analysis. Table 4.2 shows the revised POPE<br />
benefits for comparison with the original OPR AST benefits.<br />
POPE _ <strong>A6</strong> <strong>Clapham</strong> OYA _ final<br />
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SFM/PIES 2000 COMMISSION<br />
ONE YEAR AFTER STUDY - <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong><br />
Benefit AST OPR (1994<br />
prices discounted<br />
to 1994)<br />
POPE 2003<br />
Scheme (1998<br />
prices discounted<br />
to 1998)<br />
Revised POPE<br />
(1994 prices<br />
discounted to<br />
1994)<br />
Journey Time and<br />
Vehicle Operating<br />
Cost<br />
£27.6m £35.00m £31.34m<br />
Accident Benefits £10.5m £11.09m £9.93m<br />
PVB £38.2m £46.09m £41.27m<br />
Table 4.2 – Conversion of POPE Methodology Benefits for OPR AST Comparison<br />
RE-EVALUATION OF SCHEME COSTS<br />
4.11 As well as re-assessing the level of benefits accrued we have also undertaken a<br />
review of predicted and actual costs. Table 4.3 presents the predicted costs<br />
calculated before opening as part of the justification of the scheme, as well as the<br />
actual costs converted to the same price base so that direct comparisons can be<br />
made between them. Outturn prices have been converted from 2002 figures to 1994<br />
prices by using the change in RPI between 2002 and 1994 between which there was<br />
a 23% increase in prices. The prices are undiscounted total capital costs.<br />
Predicted (1994<br />
Prices)<br />
Outturn (2002<br />
Prices)<br />
Outturn (1994<br />
Prices)<br />
Construction N/A £30.19m £24.69m<br />
Land N/A £1.33m* £1.09m*<br />
Preparation N/A £0.48m £0.39m<br />
Supervision N/A £0.60m £0.49m<br />
TOTAL £30.9m £32.6m £26.7m<br />
* Does not include potential claim of £4.5m submitted under the Section 17 of the Land<br />
Compensation Act<br />
POPE _ <strong>A6</strong> <strong>Clapham</strong> OYA _ final<br />
Table 4.3 – Predicted and Outturn Scheme Costs<br />
4.12 Subsequently the undiscounted total costs need to be adjusted to take into account<br />
the difference in period to base year discussed in the recalculation of the benefits.<br />
To again enable consistency, the Present Value of the outturn costs will be based<br />
upon the factor between undiscounted cost and discounted cost in the OPR. The<br />
comparison of OPR and Outturn costs shows that although the outturn costs are<br />
higher due to the later construction date, in economic terms the schemes outturn<br />
costs were lower than what was predicted. Should the claim under the Land<br />
Compensation Act be successful to the total £4.5m claim the undiscounted outturn<br />
costs in 1994 prices would be £30.3m which is still £0.6m less than what was<br />
specified at OPR stage.<br />
4.13 For the calculation of present value in the EST it was assumed that the expenditure<br />
profile of the outturn costs was similar to the profile in the revised COBA forecasts.<br />
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5. Evaluation Summary Table<br />
INTRODUCTION<br />
5.1 In order to evaluate fully the effects of the opening of the bypass, we have<br />
undertaken a review of the Appraisal Summary Table (AST) prepared for each of the<br />
improvements. Table 5.1 presents the AST’s for the <strong>A6</strong> <strong>Clapham</strong> bypass.<br />
5.2 These AST’s summarise the predicted impacts of the two schemes across a range of<br />
different sub-objectives. The sub-objectives considered within an AST are:<br />
<br />
<br />
<br />
<br />
<br />
Environmental impacts such as Noise, Local Air Quality, Landscape,<br />
Biodiversity, Heritage and Water;<br />
Safety impacts, measuring reduction in accidents;<br />
Economy impacts including savings in Journey time and Vehicle Operating<br />
Costs, Scheme Cost and Reliability of journeys;<br />
Accessibility impacts, such as change in access to public transport, severance<br />
within communities and impact on pedestrian and other modes; and<br />
Integration, measured by how the scheme accords with local policy.<br />
APPRAISAL SUMMARY TABLES (AST)<br />
5.3 The main points to note from the ASTs are:<br />
Environment:<br />
<br />
<br />
<br />
Safety<br />
Improvement due to vehicles re-routed away from village so that 301 properties<br />
would benefit from reduced noise in <strong>Clapham</strong>;<br />
Similarly, 400 properties would see an improvement in air quality;<br />
Negative impacts forecast on landscape, biodiversity and water<br />
Significant number of accidents saved, (311 accidents through <strong>Clapham</strong> over 30<br />
years);<br />
Economy<br />
<br />
<br />
<br />
The original AST showed 7% of all vehicles were HGV’s.<br />
Significant benefits from journey time savings.<br />
Moderate benefits in terms of improvements to journey reliability.<br />
Accessibility<br />
<br />
Large benefits to severance and ‘pedestrian modes’ forecast by statement of<br />
removal of 80% of traffic from <strong>Clapham</strong> village.<br />
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Integration<br />
<br />
Positive benefit shown for as will integrate with other highway schemes, rail<br />
based park and ride; and local residential and commercial developments.<br />
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Table 5.1 – AST for <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong><br />
<strong>A6</strong> <strong>Clapham</strong>, Bedford (GOER) 1996 scheme - 5km D2 bypass Cost £30.9m<br />
PROBLEMS<br />
Poor safety and environment within <strong>Clapham</strong> (pop 3,200) where <strong>A6</strong> carries up to 21,000 vpd (7% HGV). 300 residential properties + 2 schools front<br />
on to the road. Peak hour queuing occurs on length between village and northern outskirts of Bedford.<br />
OTHER OPTIONS 2 Pelican crossings already provided in village. Large scale traffic calming scheme would have unacceptable noise, air pollution and severance<br />
effects. Other options considered include reduced standard single carriageway bypass on proposed line; an eastern bypass and improved rail services<br />
to new Bedford North station with park and ride. All have inferior benefits.<br />
CRITERIA SUB-CRITERIA QUALITATIVE IMPACTS QUANTITATIVE MEASURE ASSESSMENT<br />
ENVIRONMENTAL Noise Properties within <strong>Clapham</strong> benefit from removal of traffic<br />
No. properties experiencing:<br />
301 properties<br />
IMPACT - Increase In Noise 15<br />
experience net<br />
- Decrease in noise 316<br />
decrease in noise<br />
CO2 Local air quality Removal of through taffic by bypass will improve air quality within <strong>Clapham</strong><br />
No. properties experiencing: -409 PM10<br />
tonnes added -improved air quality 400 -2549 NO2<br />
0 - 2000<br />
- worse air quality 0<br />
Landscape <strong>Bypass</strong> partially within local areas of Great Landscape Value and would result in loss of<br />
- Slight -ve<br />
pasture land<br />
Biodiversity County Wildlife Site affected - Slight –ve<br />
Heritage No significant impacts. - Neutral<br />
Water<br />
Even with mitigation, there may still be a significant risk of polluting a sensitive<br />
- Moderate –ve<br />
watercourse and an aquifier used for public water supply during both construction and<br />
operation; and an impact on flood risk as the scheme is within a floodplain and bridges a<br />
river.<br />
SAFETY - <strong>Bypass</strong> reduces pedestrian/vehicle conflict in village and replaces a section of poor Accidents Deaths Serious Slight PVB £10.5m<br />
standard single carriageway. 311 9 94 359 54% of PVC<br />
ECONOMY Journey times & Faster journey times on new bypass<br />
Peak Interpeak PVB £27.6m<br />
VOCs<br />
4.6 mins 3.5 mins<br />
Cost PVC £19.6m<br />
Reliability Route Stress Slight<br />
Before 104% <strong>After</strong> 38% Low rel to PVC<br />
Regeneration Serves regeneration priority area? No<br />
ACCESSIBILITY Public Transport Will help to reduce peak journey times of existing local bus services - Slight +ve<br />
Severance Removes 80% of traffic from village - Moderate +ve<br />
Pedestrian/other Will improve accessibility for residents to local services Moderate +ve<br />
INTEGRATION - Complements Bedford/Kempston package proposals and facilitates proposed Bedford<br />
North rail station with park and ride. Assists proposed local residential and commercial<br />
developments<br />
- Positive<br />
COBA PVB £38.2m PVC £19.6m NPV £18.5m BCR 1.95<br />
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OUTTURN EFFECTS<br />
5.4 In order to assess the actual or outturn effects of the opening of the two<br />
improvement schemes, we have produced an Evaluation Summary Table (EST),<br />
which mirrors the appearance of the AST, and includes details of the actual subobjectives<br />
that have been evaluated.<br />
5.5 The POPE process concentrates on economy and safety impacts of new<br />
schemes at present, but this may be widened to include environmental effects,<br />
and guidance is currently being written to outline the best approach for these<br />
objectives at present.<br />
5.6 The main points to note on the EST are:<br />
Environment<br />
5.7 The environmental aspects of the schemes have not been evaluated in detail.<br />
The main premise for the benefits identified in the AST is that properties along<br />
the old <strong>A6</strong> will experience a benefit in noise and air quality due to the removal of<br />
traffic onto the bypasses, and as the traffic reductions in the villages are similar<br />
to what was predicted, it is fair to say that the environmental impacts reported in<br />
the AST are likely to have been achieved.<br />
5.8 In terms of negative forecasts such as landscape, Biodiversity and water, no<br />
assessment of these sub-objectives have been carried out at present.<br />
Safety<br />
5.9 The AST predicted significant accident savings of 311 over the 30 year period. In<br />
order to evaluate whether these predicted savings are likely we have undertaken<br />
an initial evaluation of accident savings accrued for the new schemes.<br />
5.10 Normally, it is usual for accident savings to be evaluated at least three years after<br />
opening in order to get a fair reflection in the number of accidents in the corridor,<br />
therefore this evaluation for the <strong>One</strong> <strong>Year</strong> <strong>After</strong> Evaluation is an initial view and<br />
cannot be considered as a firm conclusion at this time.<br />
5.11 Despite this caveat, we have obtained accident data for three years before<br />
opening to determine an average annual number of accidents on the <strong>A6</strong> between<br />
the Northern access/egress of the bypass onto the <strong>A6</strong> and the junction with Cut<br />
Throat Lane and a year post scheme opening between the same two points split<br />
between accidents on the old <strong>A6</strong> and on the <strong>A6</strong> bypass. Average flows for the old<br />
<strong>A6</strong> have been derived from the counts at Milton Ernest and South of Green Lane<br />
on the old <strong>A6</strong>. Table 5.2 shows the accident rates on the old <strong>A6</strong> in the year<br />
before the bypass. Average flows on the bypass have been derived from the<br />
counts between the South Roundabout and the Oakley Road slip. Table 5.3<br />
shows the accidents split by bypass and old <strong>A6</strong> based upon 3 years of ‘Before’<br />
data and one year of ‘<strong>After</strong>’ data.<br />
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Length of studied<br />
section (km)<br />
Average Flow<br />
(AADT)<br />
Average No of<br />
accidents<br />
Accident Rate<br />
(PIA/ mvkm)<br />
4.7 17,300 13 0.44<br />
Table 5.2 – Summary of Accidents on the <strong>A6</strong> <strong>One</strong> <strong>Year</strong> Before<br />
Length of<br />
studied<br />
section(km)<br />
Average Flow<br />
(AADT)<br />
No of<br />
accidents<br />
Accident Rate<br />
(PIA/ mvkm)<br />
Old <strong>A6</strong> 4.7 4,800 2 0.24<br />
<strong>A6</strong> <strong>Bypass</strong> 4.7 16,143 4 0.14<br />
Total Corridor 4.7 20,943 6 0.17<br />
Table 5.3 – Summary of Accidents on the old <strong>A6</strong> and <strong>Bypass</strong> <strong>One</strong> <strong>Year</strong> <strong>After</strong><br />
5.12 The accident rate along the <strong>A6</strong> corridor through <strong>Clapham</strong> dropped from 0.44<br />
personal injury accidents (PIA) per million vehicle kilometres (mvkm) to 0.17<br />
PIA/mvkm, a drop of 61%. This includes a drop of 45% in PIAs per mvkm along<br />
the <strong>A6</strong> through <strong>Clapham</strong> village.<br />
5.13 Table 5.4 shows the accidents by severity split.<br />
Number of Casualties<br />
Number of<br />
PIA’s<br />
Slight Serious Fatal<br />
Before 13 18 2 0<br />
<strong>After</strong> 6 8 6 0<br />
Table 5.4 – Accident Severity Splits Before And <strong>After</strong><br />
5.14 Although the annual number of accidents has shown a decrease one year after<br />
opening, Table 5.4 shows a threefold increase in serious injuries one year after<br />
opening compared to one year before opening. This is solely due to a head on<br />
collision between two cars on the old <strong>A6</strong> due to one of the cars speeding on a<br />
bend and moving across to the opposite side of the road and subsequently 5<br />
serious injuries occurred in this one single accident alone.<br />
5.15 Although the number of accidents has decreased since the opening of the<br />
bypass, the actual monetary cost of the accidents one year after study would<br />
exceed that before solely due to this one accident as the value of a serious injury<br />
is valued approximately 10 times higher than a slight accident. Analysis of<br />
accident figures back to 1999 on the <strong>A6</strong> through <strong>Clapham</strong> indicates that this<br />
accident is ‘unusual’ with only one accident between 1999 and the opening of the<br />
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bypass having more than one person seriously injured which was an accident<br />
with 3 serious injuries. Removal of these 5 serious accidents reveals an<br />
approximately constant severity split per accident before and after the opening of<br />
the bypass. Therefore, as in the POPE methodology it has been assumed no<br />
change in the cost of an individual accident at the one year after stage in the<br />
calculation of economic benefits.<br />
5.16 It is important to reiterate that this is a <strong>One</strong> <strong>Year</strong> Evaluation, and firm conclusions<br />
should really not be derived until at least three years after opening, but the initial<br />
signs are that the scheme has been successful in reducing accidents on the <strong>A6</strong><br />
through <strong>Clapham</strong>.<br />
5.17 Atkins has obtained the locations of the observed accidents, and Figure 5.1<br />
shows the location of these accidents in 2002 one year before the scheme<br />
opened and Figure 5.2 shows the location of accidents in 2003, one year after<br />
the scheme had been open. This clearly indicates a reduction in the number of<br />
accidents along this corridor.<br />
5.18 Figure 5.2 shows that the four accidents on the bypass in the opening year were<br />
at separate locations with three on the main carriageway and one on the<br />
approach to the new southern roundabout. The carriageway accidents comprised<br />
of two collisions with the central barrier attempting to avoid a collision with<br />
vehicles in front, one of which subsequently hit the vehicle in front after hitting the<br />
barrier; and one accident due to the driver losing control of the vehicle and<br />
colliding with barriers both sides and rolling over. The remaining accident on the<br />
southern roundabout was due to a car driver cutting across into the right hand<br />
lane on the entry to the roundabout and hitting a motorcyclist.<br />
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Figure 5.1 – Accidents <strong>One</strong> <strong>Year</strong> Before the Opening of the <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong><br />
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Figure 5.2 – Accidents <strong>One</strong> <strong>Year</strong> <strong>After</strong> the Opening of the <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong><br />
5.19 Within the AST the predicted accident savings over the 30 <strong>Year</strong> assessment<br />
period have been reported and in order to provide an initial view on the<br />
robustness of these conclusions we have predicted the numbers of accidents<br />
over the 30 <strong>Year</strong> assessment period.<br />
5.20 <strong>One</strong> issue regarding the AST is that although the benefits between the original<br />
AST OPR and the revised COBA were similar in monetary terms, the number of<br />
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accidents forecast to be saved in the OPR AST is 311 whilst this is subsequently<br />
lowered to 245 in the revised COBA. Based on the annual to 30 <strong>Year</strong> factors<br />
derived from the revised COBA, the actual observed annual accident saving of 7<br />
per annum equates to 220 accidents saved over the 30 <strong>Year</strong> Period on the<br />
bypassed links. The reason why this figure is lower which contradicts with the<br />
fact that we have reported higher than forecast accident benefits in Chapter 3 is<br />
that the 245 accident savings is based upon the entire modelled network within<br />
COBA whereas the POPE analysis compared the actual and modelled accident<br />
savings on just the bypass and bypassed section of the <strong>A6</strong>. In practice there will<br />
be some benefits on other roads due to reduced traffic. Whereas the complete<br />
COBA analysis will have forecast benefits due to the reduction of traffic on other<br />
roads (e.g. on roads through Oakley village), the POPE analysis only considers<br />
accident reduction on the bypass and the old <strong>A6</strong>.<br />
Accessibility Impacts<br />
5.21 The AST predicted that accessibility benefits would accrue in terms of reduced<br />
severance and improved conditions for pedestrians and other modes, and these<br />
would result in an 80% reduction in traffic in the village.<br />
5.22 Outturn traffic volumes suggest that 60-75% of the <strong>Clapham</strong> through traffic was<br />
removed from the village suggesting that the accessibility benefits outlined in the<br />
EST are moderate.<br />
Integration<br />
5.23 The bypass complements the A421 Bedford bypass and based on proposed<br />
future developments, it will also complement the proposed Bedford Western<br />
bypass which would link the <strong>A6</strong> <strong>Bypass</strong> to the A421 which is planned in 2007/08.<br />
Plans also exist for a possible Park and Ride site near the <strong>Clapham</strong> bypass.<br />
Summary<br />
5.24 A summary of effects across all evaluation sub-objectives are included in the<br />
EST in Table 5.5.<br />
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Table 5.5 – EST for <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong><br />
<strong>A6</strong> <strong>Clapham</strong>, Bedford (GOER) 2002 scheme - 5km D2 bypass Cost £26.7m<br />
PROBLEMS<br />
SOLVED<br />
Indication of reduction in traffic flows on the <strong>A6</strong> through <strong>Clapham</strong> from between 15,000 - 23,000 vehicles per day to 2,000 – 8,.500 vpd. Proportion of<br />
HGV’s using <strong>A6</strong> through <strong>Clapham</strong> reduced from 8% to 2%.<br />
OTHER OPTIONS Not assessed<br />
.<br />
CRITERIA SUB-CRITERIA QUALITATIVE IMPACTS QUANTITATIVE MEASURE ASSESSMENT<br />
ENVIRONMENTAL Noise<br />
No assessment specifically made – but AST conclusions are likely to be valid as traffic<br />
- Large +ve<br />
IMPACT<br />
volumes have been significantly reduced in village<br />
Local air quality<br />
No assessment specifically made – but AST conclusions are likely to be valid as traffic<br />
volumes have been significantly reduced in village<br />
Large +ve<br />
Landscape Not assessed -<br />
Biodiversity Not assessed -<br />
Heritage No assessment specifically made – unlikely to be significant impacts. - -<br />
Water<br />
Not assessed - -<br />
SAFETY - <strong>Bypass</strong> reduces pedestrian/vehicle conflict in village and replaces a section of poor<br />
Accidents Saved PVB £9.9m<br />
standard single carriageway. 220<br />
ECONOMY Journey times & Faster journey times on new bypass<br />
Peak Interpeak PVB £31.3m<br />
VOCs<br />
5 mins 4.5 mins<br />
Cost PVC £18.4m<br />
Reliability Route Stress Slight<br />
Before 79% <strong>After</strong> 28% Low rel to PVC<br />
Regeneration Not assessed - -<br />
ACCESSIBILITY Public Transport Not assessed - -<br />
Severance 60-75% of traffic has been removed from the village, thus greatly reducing the<br />
severance.<br />
- Moderate +ve<br />
Pedestrian/other<br />
INTEGRATION -<br />
60-75% of traffic has been removed from the village, thus greatly improved the<br />
environment for pedestrians and others.<br />
Moderate +ve<br />
COBA PVB £41.3m PVC £18.4m NPV £22.9m BCR 2.24<br />
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6. Summary of Conclusions<br />
6.1 The Highways Agency has a requirement to carry out re-evaluations of trunk road<br />
schemes recently implemented by the Department of Transport. The purpose of<br />
these re-evaluations is to provide a back check of the levels of benefit accruing<br />
from new schemes and to determine how far the department achieves the<br />
objectives and benefits it claims from its road programme.<br />
6.2 In summary, the main points to note from the <strong>One</strong> <strong>Year</strong> Evaluation of the <strong>A6</strong><br />
<strong>Clapham</strong> <strong>Bypass</strong> TPI Scheme are;<br />
Before the improvements scheme the old <strong>A6</strong> route through the village of<br />
<strong>Clapham</strong> carried around 15,000 – 23,000 vehicles per day (on an average<br />
weekday);<br />
The <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong>, which officially opened on 12 th December 2002,<br />
carried around 17,000 vehicles per day, a month after opening;<br />
A year later, the traffic volumes on the bypass has grown to around 18,500<br />
vpd;<br />
<br />
75% of traffic has been removed from the bypassed section of old <strong>A6</strong> in<br />
<strong>Clapham</strong> suggesting that the schemes have been successful in removing<br />
through traffic from the village;<br />
The OPR AST predicted a total benefit of £38.2m comprising of £27.6m<br />
journey time and VOC savings with £10.5m of accident savings in 1994<br />
prices discounted to 1994. The POPE methodology produced total benefits<br />
of £41.3m comprising of £31.3m journey time savings and £9.9m of accident<br />
savings in 1994 prices discounted to 1994.<br />
Journey time information suggests that time savings of between 2 to 3<br />
minutes are being forecast for journeys along the 5km length of the bypass<br />
compared to the corresponding route along the <strong>A6</strong> through <strong>Clapham</strong>.<br />
<br />
<br />
<br />
<br />
The completion of the <strong>A6</strong> has led to a reassignment of traffic onto the road<br />
and new trips, and the benefits from these trips have not been incorporated<br />
as the POPE methodology.<br />
The predicted scheme costs for the <strong>A6</strong> <strong>Clapham</strong> bypass were estimated to<br />
be £30.9m in 1994 prices. This outturn costs were £27.7m in 1994 prices<br />
although this could increase as there are still Land Compensation Act claims<br />
outstanding.<br />
An Evaluation Summary Table has been prepared to be directly compared<br />
with the AST’s prepared before opening. These show that the prediction of<br />
the relief of traffic in <strong>Clapham</strong> was robust and that the accident savings<br />
predicted were robust.<br />
The <strong>A6</strong> <strong>Clapham</strong> <strong>Bypass</strong> has led to a reduction in the number of accidents in<br />
the corridor, where up to 7 personal injury accidents have been saved in the<br />
first year after opening.<br />
6.3 Evaluation of other sub-objectives within the AST will be carried out as part of the<br />
Five-<strong>Year</strong> <strong>After</strong> assessment, which will consider accident reductions in more<br />
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detail, as well as how land use has changed in the area as a result of the <strong>A6</strong><br />
<strong>Clapham</strong> <strong>Bypass</strong>.<br />
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