Towards performance-based route selection guidelines for heavy vehicles (the dynamics of heavy vehicles over rough roads)

With an increasing number of transport operators seeking permits to operate nonstandard or purpose-built vehicle types, information is required to assist road authorities to determine which vehicle types could operate on the road network without compromising the safety of other road users. A project was created by ARRB TR to develop guidelines for determining route access for heavy vehicles. This project was developed in conjunction with the state road authorities, the National Road Transport Commission and the transport industry to obtain an understanding of the road space requirements for a range of common vehicle types. This project is the subject of this thesis. Two series of field experiments were conducted with six common heavy vehicle types on public roads west of Parkes NSW. Information collected during these full-scale experiments was used to increase the knowledge of the dynamic behaviour of these vehicles and to develop model route access guidelines. Data obtained from these field experiments also provided information to validate computer models and simulation outputs. This thesis showed that: 1) There was experimental evidence to demonstrate that vehicle lateral movement is excited by differences in vehicle wheelpath profiles (point-by-point pavement crossfall), which make a contribution to trailing fidelity (swept width), offtracking and swept path; 2) Vehicle type and speed are prime influences on the lateral movement of the rear trailer and therefore an important input into the model route access guidelines. Notwithstanding the practical and safety implications of applying different speed limits for various vehicle types, speed is a prime contributor to vehicle lateral movement and should be considered when determining route access; 3) Limited lateral position information suggested that one driver of two vehicle types position the vehicles so that the tyres on the rear trailer track on the sealed pavement and not on the pavement shoulder; 4) Based on a statistical analysis of the data obtained from the small sample which only considered the average crossfall of each test section the relative importance of the key parameters was (highest to lowest), IRI, vehicle speed and vehicle type. It was shown that good estimates of lateral movement can be obtained using a double integration technique of the measured lateral acceleration, without applying compensation for the trailer roll or the pavement crossfall. It is recommended that route access guidelines be developed using the lateral performance of a larger sample of vehicles in each class of heavy vehicles operating over a larger range of road types. The route access guidelines should contain a matrix of information on vehicle type/length, pavement condition roughness/profile and lane width. This would provide operators and regulators with a desk-top assessment tool for determining route access.