Dynamic rollover threshold of articulated freight vehicles

Different measures of relative roll instability of heavy vehicles are inves tigated to determine their dynamic rollover characteristics. Analytical mod els of different vehicle combinations are presented and a concept of effect ive lateral acceleration is proposed to characterize the relative roll inst ability under dynamic directional manoeuvres. The analytical models for a f ive-axle tractor semi-trailer combination and an eight-axle A-train double are analysed to establish the dynamic rollover threshold based upon relativ e roll instability criterion and effective lateral acceleration. The dynami c rollover threshold of the vehicle, derived for different suspension prope rties and operating conditions, is compared with the corresponding static r ollover threshold of the vehicle. From the results of the study, it is esta blished that dynamic rollover threshold based on effective lateral accelera tion in most cases is either slightly lower or equal to the static rollover threshold acceleration. The difference between the dynamic and static roll over thresholds is less than 5% for the vehicle configurations and the stee ring manoeuvres considered in the study. The static rollover threshold may thus be conveniently employed to estimate the dynamic rollover propensity o f heavy vehicles.