On Lateral Stability of Heavy Vehicle Combinations - Linking Accident Analysis and Vehicle Dynamics

Licentiate thesis, 2008

One of the hazardous motions of heavy trucks is lateral instability which can be defined as deviation from driver intended path due to skidding of the vehicle. Lateral instability is associated with 9% of heavy trucks involved in traffic accidents, which represents a considerable figure when translated to real accidents. For instance in the US, this can be translated into about 36000 traffic accidents each year which could have been mitigated or even prevented. The objective of the research presented in this thesis is to develop reality-based lateral stability control strategies for heavy trucks. By reality-based it is meant that the control strategy should be designed to reduce heavy trucks accidents due to lateral instability and should be evaluated in the same scope. To fulfill this objective, an analysis of heavy truck accidents based on the Large Truck Crash Causation Study database was conducted. Accident scenarios were studied and a category of critical maneuvers causing loss of control was identified. Based on the accident analysis results, relevant existing test maneuvers were adapted for trucks and compared; the sine with dwell maneuver was selected as the most suitable test for evaluation of lateral stability of heavy trucks. Furthermore, some performance measures were proposed based on a series of field tests. As the first insight into the development of lateral stability control strategies for heavy trucks, Rear Axle Steering (RAS) for a single unit truck was investigated. It was shown that by RAS, considerable safety benefits and enhancement in driver comfort can be gained.