NRA TA 85 Guidance on Minor Improvements to National Roads

<strong>NRA</strong> <strong>TA</strong> <strong>85</strong> <strong>Guidance</strong> on
Minor Improvements to
National Roads
2012 <strong>NRA</strong> CONFERENCE
LIMERICK
Presented by:
Eddie Murphy &
Bryan Kennedy
Kildare National Roads Office

What is <strong>NRA</strong> <strong>TA</strong><strong>85</strong>/11 and what is it’s purpose?
• It is a Technical Advice Note that provides guidance on the
design principles to be considered when implementing Minor
Improvement and Road Safety Improvement Schemes on
National Roads.
• <strong>NRA</strong> <strong>TA</strong><strong>85</strong>/11 supersedes the October 2006 version of <strong>NRA</strong>
IAN <strong>85</strong>/06 (Minor Improvements to Existing National Roads).

What does it apply to?
• Minor Improvement Schemes
• Road Safety Improvement Schemes
What doesn’t it apply to?
• Maintenance Schemes

Definitions
Minor Improvement Scheme
“Is an upgrade to an existing section of substandard road less
than 2km in length where a design element or combined set of
design elements are improved”.
A Road Safety Improvement Scheme
“Is a Schemes that specifically targets sections of the network
with high collision rates to improve road safety”.

Definitions
Maintenance Schemes
“predominantly involve pavement works and other road feature
maintenance works such as;
• overlay and inlay works which regulate the camber of the
existing road i.e. return the camber to its original shape;
• the introduction of new traffic signs and road markings”

Minor Improvements
Objective:
The objective of a Minor Improvement Scheme is to achieve a
localised improvement appropriate to, and consistent with, the
characteristics of the adjacent sections of the route.
The aim of a Minor Improvement Scheme should be:
• To improve Road Safety and
• To make better use of the existing road network

Minor Improvements (contd.)
Example of elements of the road that might be improved would
include:
• Applying superelevation in accordance with <strong>NRA</strong> TD 9
• Improvements to the horizontal and vertical alignment
• Upgrading the road cross-section
• Sightline Improvements at junctions

Road Safety Improvement Schemes
Objective
“…to achieve a reduction in the frequency, and severity of
collisions which have occurred on this section of the
Network”

Who is the Road Authority?
• For Minor Improvement Schemes the Road Authority shall be
the relevant Local Authority responsible for the Scheme.
Relevant Section in the <strong>NRA</strong>
• Minor Improvement Scheme – Pavement Maintenance
Section, Network Operations.
• Road Safety Improvement Schemes – Road Safety Engineering
Section.

Preliminary Design Report
Objective
“…to address and present issues relating to compliance with the
relevant parts of the <strong>NRA</strong> DMRB for the options considered”
Section 2.2 of <strong>TA</strong><strong>85</strong> states
“ A copy of the Preliminary Design Report shall be issued to the
<strong>NRA</strong> Standards Section for their information”

Contents of The Preliminary Design Report

Preliminary Design Report
Table 2/1 of <strong>TA</strong><strong>85</strong>/11

Preliminary Design Report

Chapter 3 Design Standards
Design Speed
• Related to road characteristics, not mandatory speed limit.
• Geometric Elements consistent with road character.
• Calculated for the section of road being improved and for the
2km either side using the method contained in Chapter 1 of
<strong>NRA</strong> TD9 “Road Link Design”.

Chapter 3 Design Standards
Horizontal Alignment
• Shall be consistent with the existing road network for 2km
either side of the proposed scheme.
• Shall consider the impact of any realignment on existing
accesses and junctions.
• Shall ensure that the proposed horizontal alignment design
does not introduce new safety problems

Chapter 3 Design Standards
Horizontal Alignment
• Where adverse camber is present superelevation shall be
designed in accordance with <strong>NRA</strong> TD 9 “Road Link Design”.
• Where this cannot be achieved superelevation should be
consistent with the level of superelevation provided on
adjacent sections as a minimum, and shall be recorded as a
Departure.

Chapter 3 Design Standards
Horizontal Alignment
• Applied superelevation shall not adversely affect existing
drainage, vehicular accesses or junctions .
• Examples from Chapter 4 of <strong>NRA</strong> <strong>TA</strong> <strong>85</strong>/11

Chapter 3 Design Standards
Vertical Alignment
• Alterations shall be carried out to satisfy the Desirable
Minimum requirements of <strong>NRA</strong> TD 9 “Road Link Design”.
• Where it is not possible to meet the Desirable Minimum
requirements it shall be recorded as a Departure.
• Shall ensure that the proposed vertical design does not
inadvertently introduce hidden dips.

Chapter 3 Design Standards
Vertical Alignment
• Example from Chapter 4 of <strong>NRA</strong> <strong>TA</strong> <strong>85</strong>/11

Chapter 3 Design Standards
Cross-Section
• Cross-section should comply with Table 6/1 of <strong>NRA</strong> TD 9
“Road Link Design” where possible & should also consider the
future route strategy for the existing road.
• Any reduction in cross-section shall be recorded as a
Departure. Example from Chapter 4 of <strong>NRA</strong> <strong>TA</strong> <strong>85</strong>/11

Chapter 3 Design Standards
Overtaking Value
• Provide the best improvement to overtaking opportunities
that can be economically devised
• Principle objective of some minor improvements may be to
provide enhanced overtaking opportunity (achieve the
minimum overtaking value specified in Table 7/3 of <strong>NRA</strong> TD 9
“Road Link Design”.
• Shall ensure that overtaking and non-overtaking sections
clearly identified

Chapter 3 Design Standards
Overtaking Value
• Considerations should be made of nearside overtaking
sections at junction locations
• Examples from Chapter 4 of <strong>NRA</strong> <strong>TA</strong> <strong>85</strong>/11.

Chapter 3 Design Standards
Junctions & Access Modifications
• Minor improvements involving upgrades to existing junctions
shall comply with the requirements of <strong>NRA</strong> TD 9 and <strong>NRA</strong> TD
41-42 “Geometric Design of Major/Minor Priority Junctions
and Vehicular Access to National Roads” where possible.
• Forward visibility and visibility splays at junctions and
accesses, which are currently below <strong>NRA</strong> DMRB standards,
shall not be adversely affected and where possible should be
improved.

Chapter 3 Design Standards
Junctions & Access Modifications
• Departures shall not be permitted to reduce visibilities below
standard where existing visibilities are above <strong>NRA</strong> DMRB
standards. Examples from Chapter 4 of <strong>NRA</strong> <strong>TA</strong> <strong>85</strong>/11.

Chapter 3 Design Standards
Safety Barrier
• If the Design Speed is 100km/h or greater, the requirements
of <strong>NRA</strong> TD 19 Safety Barriers shall apply.
• A review of the operational characteristics of any existing
barriers for compliance with <strong>NRA</strong> TD 19 shall be carried out.
• The operational characteristics of any existing safety barriers
which are retained shall not be affected.

Chapter 3 Design Standards
Safety Barrier
• Where it is not feasible to apply the requirements of <strong>NRA</strong> TD
19 the following alternative actions shall be considered;
Removal of the hazard.
Relocation of the hazard to a safer position.
Redesign of the hazard to reduce the danger to road users.
Provide warning signage in advance of the hazard.
Mitigate the presence of the hazard by improved road edge
delineation.
Redesign of the road layout to lower the risk.

Chapter 3 Design Standards
Safety Barrier
• Minor improvements schemes with a Design Speed less than
100km/h, safety barriers will generally not be required, unless
it is considered to be a specific hazard.
• However a review of TD19 Safety Barrier is being carried out
and all National Roads will be subject to a Safety Barrier Risk
Assessment in the future.
• The following is the procedure to be followed for the Safety
Barrier Risk Assessment;

Chapter 3 Design Standards
• The Hazard location and type will be identified by Designers.
• The Designers to remove, relocate or redesign hazards to
remove the need for a safety barrier.
• The need for a barrier will be determined by a designer risk
analysis based on the following data:
Collision Data
Sinuosity
Run off road Data
AADT
• Locations will be classified as High, Medium and Low Risk

Chapter 3 Design Standards
Drainage
• Shall ensure that surface and sub-surface drainage provisions
in accordance with HD 33, as amended by the <strong>NRA</strong>, are
included in the design.
• Where existing road drainage provisions are to be
incorporated an assessment of the adequacy of the drainage
system shall be made and should include a review of the
superelevation and longitudinal gradient.

Chapter 3 Design Standards
Traffic Signs & Road Markings
• Improvements to existing signs, road markings and reflectors
shall comply with the requirements of the Traffic Signs
Manual.

Chapter 3 Design Standards
Non Motorised Road Users
• The design shall address the needs of Non Motorised Road
Users.
• An assessment of existing footways/cycle tracks in the vicinity
of the minor improvement shall be undertaken.
• Where footways/cycle tracks are required, the verge shall be
widened accordingly to accommodate these features.

Chapter 3 Design Standards
Road Safety Audits
• All schemes shall be subject to Road Safety Audits
During Design
Completion of Construction
• Road Safety Audits should be carried out in accordance with
<strong>NRA</strong> HD 19 Road Safety Audits.

Example 1: N72 Cappagh Bends
• Realignment of Horizontal Geometry
• Realignment of Vertical Geometry
• Application of Superelevation
• Nearside Overtaking Opportunity
• Increase in Stopping Sight Distance
• Increase in Visibility from Junction
• Removal of Road Side Hazards
• Installation of New Safety Barrier

Thank You for Your Attention
We will now take any questions