AP-G84/04 Best practice in road use data collection, analysis ... - WIM

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Accessed by AR - ARRB TRANSPORT RESEARCH on 04 Feb 2005 Austroads 2004 — 14 — Best Practices in Road Use Data Collection, Analysis and Reporting Traffic counting programs are well established and documented through a series of guides beginning with NAASRA (1982) and the two versions of GTEP Part 3 (Austroads 1998a and 2004). A national review of traffic counting procedures (Roper 2001) and subsequent recommendations (Bennett 2002), addressed the issues of additional data collection facilities and consistency across the reporting RAs. The studies of Roper (2001), Bennett (2002), a parallel research activity addressing an international literature review on consistency of data (Martin and Chiang 2002), and a review of the current traffic data of the RAs (Roper et al. 2002), led to the Road Use Data Workshop in October 2003 involving representatives from the RAs specifically addressing the key issues in traffic data (Luk and Karl 2003). In addition to the studies and Workshop already mentioned, a range of other sources (such as the US FHWA, the European Commission and other reports) were accessed in the preparation of this section. The NAASRA (1982) Guide provided a solid grounding for RAs on which to base their traffic counting operations and, in general, this has resulted in a consistent and diverse set of traffic data available from RAs, as can be seen in Figure 6 (Roper et al. 2002). A cursory examination of the tables will show that most of the tabulated data items of interest are already reported by most of the RAs. 4.2 AADT and VKT Estimation Annual Average Daily Traffic (AADT) and Vehicle-Kilometres Travelled (VKT) are two of the most commonly used descriptors of traffic derived from raw traffic counts. Data expressed in AADT and VKT are universally understood. This section begins with brief introductions to AADT and VKT, followed by discussions on accuracy and adjustment factors. 4.2.1 AADT AADT is the Average Annual Daily Traffic passing a roadside observation point over the period of a calendar year. It can be obtained by a number of ways. For example, it is obtained by measuring the total volume of traffic passing the observation point over a year and then divided by the number of days in that year, i.e. AADT = n ∑Vi / n i= 1 where Vi = the total traffic counts on day i and n is the number of days in that year (n can be 365 and 366 days). Some jurisdictions adopt n = 365.25 days but the difference should be small. The production of AADT data would be straightforward if all counting stations were to operate without fail for every day of the year, recording daily traffic data. However, in reality, reliability is not 100% and not every counting station is a permanent station that operates all year round. AADTs derived from permanent or pattern sites may require ‘plugging the gaps’ due to missing data. Such adjustments are preferably minor and involve a few days of lost or corrupt data over a twelve month period. Permanent sites, however, comprise only a small amount of the traffic counting network. The issue of handling missing data will be addressed in Section 6.
Accessed by AR - ARRB TRANSPORT RESEARCH on 04 Feb 2005 (a) Traffic volume data items by jurisdiction Data Item ACT NSW NT QLD SA TAS VIC WA NZ ADT AADT AWT AAWT Midweek Volume VKT DHV Growth & Trends in AADT Growth & Trends in VKT (b) Traffic flow data items by jurisdiction Data Item ACT NSW NT QLD SA TAS VIC WA NZ Ranking in highest hourly flows Distribution of Hourly Flows through the year Directional Patterns Directional/Lane Distribution of traffic Seasonal Patterns Use of Aggregated Data by Time or Location (e.g.: 15, 30, 60-minute intervals etc.) (c ) Traffic composition data items by jurisdiction Data Item ACT NSW NT QLD SA TAS VIC WA NZ Use of Austroads Vehicle Classification schemes Other schemes Traffic Composition (e.g. % HV, % Artic. % Rigid, % Combination, etc.) Austroads 2004 — 15 — Best Practices in Road Use Data Collection, Analysis and Reporting (d) Weigh-in-motion data items by jurisdiction Data Item ACT NSW NT QLD SA TAS VIC WA NZ Weigh-in-Motion (WIM) Truck Weight Data Freight Mass (e) Other data items by jurisdiction Data Item ACT NSW NT QLD SA TAS VIC WA NZ Functional Classification of Road Geographical Regions Types of Counts Collected (e.g., Turning Counts, Axle Counts, Vehicle Counts, Bicycle Counts) Other Types of Traffic Data Collected (e.g., Travel Time Surveys) (f) Adjustment factors by jurisdiction Data Item ACT NSW NT QLD SA TAS VIC WA NZ Seasonal Adjustment Factors Expansion Factors (e.g.. 12 hour count to 24 hour count) Other Adjustment Factors (e.g.. public holiday, weekends, etc ) Daily Flow Factors Figure 6 – Survey of road use data needs amongst Road Authorities
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AP-G84/04 Best practice in road use data collection, analysis ... - WIM

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