Analysis of the dynamic response of heavy trucks on highway curves under actual operating conditions

The dynamic response of a 5-axle tractor-trailer unit carrying loads of varying weight was evaluated under actual operating conditions as it travelled over the highway and through curves of varying radius. To complete the over-the-road tests, a Data Acquisition System (DAS) was designed and developed for the Transportation Research Group to their specifications. The equipment can record information on a vehicle moving at highway speeds by use of a number of sensors which are interfaced to the central processing unit. The unit collects data on tri-axial accelerations at three different locations on the truck, steering inputs from the driver, vehicle speed and trailer roll angle.; Test runs were performed over a total of 1,110 km of highway from Moncton, New Brunswick to North Sydney, Nova Scotia. Three load configurations were tested: empty; loaded with Less-Than-Truck-Load (LTL) to 95% of trailer's capacity; and, loaded with bottled water packed in boxes to 55% of the trailer volume.; The results provided measurements of the lateral accelerations generated on the trailer as the vehicle moved along tangents and through curves. It was found that in most cases the average level of lateral acceleration exhibited on each vehicle unit exceeded the expected values as calculated for the selected curves based on geometric design characteristics. Comparisons of actual results with theoretical considerations confirm this observation.; The results from the research indicate that the greatest change in lateral acceleration at tangent points occurred on the trailer carrying bottled water—the heaviest of the loaded units. The values obtained from the unit carrying LTL suggest that the non-uniform load distribution exerted an influence on the level of change in lateral acceleration on the trailer at the tangent points.; Analyses of the field data indicated that under certain motion and load conditions, occasional peak lateral accelerations values generated were in the vicinity of rollover threshold values estimated for the instrumented vehicle. These results confirmed that the potential existed for the vehicle to roll over at certain points along the horizontal curves.; Although the vehicle travelled at or below the posted speed limit in the majority of cases, the lateral accelerations recorded on the trailer exceeded the expected lateral accelerations under all load configurations. The lateral acceleration generated on the trailer was found to be a function of gross vehicle weight, the time spent by the vehicle on the curves, and the length of the curves. The road geometry also affects the vehicle's response. Therefore, more consideration should be given to these issues by road designers and traffic engineers in an effort to better accommodate heavy truck traffic without compromising the safety of all road users. The research findings indicated that the effect of wind forces on the trailer requires further analysis.