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Heavy vehicles with high centres of gravity are prone to rollover accidents. For a given height and width, stability is affected by suspension design. In articulated vehicles, the matching of the tractor and trailer suspensions, as well as the degree of coupling between tractor and trailer, affects the stability of the combination. A number of loaded articulated combinations with high centres of gravity were tested on a specially-constructed tilt deck. Parameters including lateral load transfer at each axle group, deflections of the sprung and unsprung parts of the suspensions, movement at the fifth wheel coupling and torsional deflection of the chassis were measured up to the point of first wheel lift. A computer model of the rollover process was also developed. The effects of suspensions, couplings, tyres and chassis on the rollover limit are discussed.

The development of larger more productive innovative heavy vehicle combinations for public road operations relies heavily on proving new vehicle concepts to both government and local authorities. In a number of cases simulation modelling has proved to be a useful tool in showing that proposed innovative heavy vehicle concepts are safer and more efficient alternative to conventional equipment. This paper provides examples of the use of AUTOSIM™ in developing custom yaw/roll and yaw/roll/pitch models for investigating the dynamic performance of combination vehicles. Models are described for large innovative road trains which incorporate B-doubles units. Consideration is given to the modeling of the trailing fidelity of these vehicles on non-planar surfaces and examples of model outputs for combination vehicles operating on various three-dimensional features are presented.