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

Accessed by AR - ARRB TRANSPORT RESEARCH on 04 Feb 2005
4 TRAFFIC COUNTING PROGRAM
Austroads 2004
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Best Practices in Road Use Data Collection, Analysis and Reporting
This section addresses best practices in a traffic counting program. It begins with a brief
description of the current situation in traffic counting programs amongst road authorities (RAs).
The description is from the perspective of traffic counting techniques and methods as well as from
the perspective of the RAs having to balance rigour in their traffic counting programs against an
increasing rate of change and variation in traffic flows caused by economic activity, increased
scrutiny and user demands as well as budgetary cost pressures (Section 4.1). This section covers
best practices in the three main areas of traffic counting programs: obtaining the raw data (Section
4.2), transforming the raw data into AADT and VKT (Section 4.3) and reporting of the raw and
transformed data (Section 4.4).
4.1 Background
Traffic counts and classifications are the basic raw materials for the study and analysis of traffic,
forming a key input and influencing the design, maintenance and management decision making of
every RA. In fact, the importance of traffic data extends beyond the interests of each RA to include
various commercial users (for planning and commercial studies) and other government agencies at
a national level on policies leading to an integrated national land transport infrastructure network.
In general, there are three main themes of traffic data:
Variation of traffic flow by location,
Time-variation of traffic flow,
Composition of the traffic flow.
The above data are collected by counting stations. Counting stations are located at various points
in the road network to ensure the collection of a representative sample of data that will, in isolation,
report on particular road segments or corridors and, in aggregate, report on the entire road network
itself. Two types of counting stations are employed. They are the Permanent Counting Stations
(PCS, also known as ‘Pattern Stations’) and Short-term Counting Stations (SCS, also known as
‘Sample’ or ‘Coverage’ Stations). Pattern Stations continuously monitor or frequently sample traffic
to determine patterns and seasonal fluctuations. Such stations are permanent or semi-permanent
for counting over a defined ‘season’ (usually a year). Short-term stations are counting stations that
are utilised for brief traffic surveys ranging from periods of a few weeks to one hour, with a typical
sample site counting traffic for seven consecutive days.
Traffic counting faces pressure from users who want additional data for reports and projects, as
well as from owners who want improved cost efficiencies. Out-sourcing many aspects of data
collection and maintenance is more commonplace today and one particular traffic data unit in a RA
has become totally off-budget, requiring it to secure customers amongst the various divisions
within the parent RA.
At the same time, rapid changes in the economy, the development of toll roads, increased freight
flows, changing vehicle regulation and technology have resulted in potentially large changes in
traffic patterns as well as the potential to use new technology to track and count vehicles.
In this environment, it is timely to revisit the fundamentals of traffic counting programs. The
contribution of the practitioners in this field through the earlier fieldwork and the recent Austroads
Road Use Data Workshop has been invaluable towards a common sense approach in addressing
and developing best practice for traffic counting programs.