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

Accessed by AR - ARRB TRANSPORT RESEARCH on 04 Feb 2005
Austroads 2004
— 52 —
Best Practices in Road Use Data Collection, Analysis and Reporting
The issue of utilising WIM equipment as part of a traffic counting program is also discussed in
some detail. As long as all lanes of traffic are monitored at a WIM site, the traffic count data (and
WIM data) should add extra value to a counting program. The related issue of correlating classified
count data with vehicle mass data is more complex and there is not much information published on
this topic. In practice, if the ratio of loaded and unloaded vehicles at a counting station is consistent
with a nearby WIM site, then an accurate estimate of pavement loading can be determined.
Road use data can come from many sources meeting a variety of needs. This leads to the issues
of data integration and accessibility. Many stakeholders are consequently involved. This report
provides a stakeholder consultation model from Main Roads WA. These issues are rather involved,
and RAs at present have quite varied policies on data availability and its pricing. As the trend to
outsource data continues amongst RAs, third parties may become both supplier and purchaser of
road use data. While these issues were discussed at the October 2003 Workshop and described in
some detail in this report, they will continue to confront RAs in the future. It is appropriate to
develop, as a future research task, an appropriate policy or business model in this area of data
integration, accessibility and pricing.
In summary, a list of recommendations is as follows:
1. Vehicle detection - a pair of axle sensors should be considered where possible to give better
accuracy, better distinction by direction, and the ability to produce classified counts through
axle configurations. If a single axle is used, it is a recommended practice to correct for traffic
composition and convert axle-pairs into vehicle counts for reporting purposes.
2. Vehicle classification - the current Austroads vehicle classification be maintained but allowing
sub-classes as variations of the basic system. It is appropriate to introduce a new notation to
designate different jurisdictional versions, e.g. the Austroads (Vic) for the Victoria version.
3. Error bin - an error bin (no. 13) be introduced into the Austroads system as good practice to
indicate the quality of the classified counts. The number of error counts should be monitored
and, if these remain high relative to the traffic stream, the reasons for these errors should be
identified and the problem rectified. The inclusion of error counts in bin 13 in the total counts
requires some judgement. If the number of error counts is high relative to the total counts, it
is necessary to identify the reasons for such a situation before error counts are included. If it
is deemed appropriate to distribute bin 13 vehicles, the method of distributing across all bins
from 1 to 12 or only to bin 1 can be considered, or both methods are used and guided by
relevant local knowledge.
4. Vehicle classification by length - a variety of threshold values are being used for vehicle
classification by lengths. It is recommended that RAs come to agreement on a single
classification system by lengths. Some empirical work using a standard loop design would
appear necessary. On reaching agreement, the Austroads system should incorporate a
definitive multi-bin system by vehicle lengths as a component of the total Austroads
classification system. This harmonisation should facilitate equipment manufactures to design
their equipment for a single specification.