Road geometry evaluation for heavy vehicle stability

Road geometry parameters such as curve radius, crossfall, superelevation on bends, transitions, rutting and surface unevenness all have an influence on the rollover stability of a heavy vehicle. Using advanced 3D multibody dynamics simulation, Advantia evaluates road designs and survey data in terms of the impact on heavy vehicle stability. Project summary by Rob Di Cristoforo.

Road agencies, road construction engineering firms and legal teams in road crash matters all need to know one thing: Does this particular section of road pose an unacceptable risk of heavy vehicle rollover?

One way to answer that question is to drive a truck along the section of road at the desired speed and see if it exceeds a safe level of lateral load transfer. Advantia does just that, but in a virtual environment using TruckSim.

TruckSim is a software tool for simulating and analysing the dynamic behaviour of medium to heavy trucks, buses and articulated vehicles. Advantia uses TruckSim as an Accredited Assessor under the PBS (Performance Based Standards) Scheme. It reflects all of the important features of a heavy vehicle’s mechanical design that enable a faithful representation of the actual vehicle’s dynamic behaviour to be developed.

View the below video clip for an example of TruckSim in action.

Now by running one of these advanced models over a particular section of road, either from a design data set or from survey data taken from an existing road, one can quickly determine the level of safety of the road in terms of the likelihood that the vehicle will become unstable when negotiating that section of road.

Ideally, a heavy vehicle should be able to negotiate any section of road at an appropriate speed without exceeding a Load Transfer Ratio of 0.6.

This method can be used to evaluate new road design options for:

  • Roundabouts
  • Freeway interchanges
  • Winding roads on steep terrain.

You can tailor the analysis by using the types of heavy vehicles you expect will access the road. If the analysis suggests a revision of the design, you can then test the revised design to demonstrate the level of improvement.

In the case of a road crash re-construction, a section of road may be surveyed to obtain the required dataset. An actual crashed vehicle can be modelled in the software and an analysis can be conducted to investigate, for example, the likely speed that a vehicle was doing when it rolled over, or the likelihood that a failed suspension or tyre may have been the cause of the crash.

A road can be constructed with varying levels of detail, including shoulder drop-offs, ruts, pot holes, crossfall variations and surface unevenness.

Please contact Advantia for more information.