A new report by Austroads considers how to more accurately model heavy vehicle movements during interrupted traffic flows.

The publication was developed in response to increasing heavy vehicle traffic on arterial road networks because the length and low acceleration capability of heavy vehicles can reduce traffic flows, especially at intersections.

Road agencies are concerned that traffic modelling software such as SIDRA, LINSIG, AIMSUN and VISSIM cannot correctly calculate the capacity of arterial roads where there are many heavy vehicles because of the inaccurate scenario testing that ultimately affects policy analysis.

Austroads commissioned a research project to develop parameters that could accurately model heavy vehicle movements during interrupted traffic flows in Australia and New Zealand.

“To collect the data serving as a basis for parameter development, we conducted field surveys, including video surveys, at four intersections with signals and one intersection without signals in Perth and Melbourne,” said Dr Young Li, Senior Professional, Future Transport Systems, ARRB and a co-author of the report.

“We surveyed vehicle length, clearance space, acceleration, start-up and saturation headways, through and turning speeds, critical gap and follow-up headway and monitored five heavy vehicle types: rigid trucks, single articulated trucks, B-double trucks, double road trains and triple road trains.”

The report developed a set of heavy vehicle parameters for use as a guide when road agencies are applying them to similar modelling conditions used in the study – arterial roads that are relatively flat and in speed limit zones of between 60 to 70 kilometres an hour.

“Application of the parameters to dissimilar traffic and highway conditions should be reviewed using field observations,” said Dr Li.

Report recommendations include testing the parameters under more varied conditions and at different sites to improve confidence in them and testing more specific vehicle types.

Dr Li will host a webinar on Monday 9 December giving an overview of the study. There is no fee for the session, but registration is essential to join live, or to receive a link to its recording. Register here.

Download the Austroads report: Improving the Reliability of Heavy Vehicle Parameters to Support More Accurate Traffic Modelling in Australia and New Zealand