Frank R Wilson

HEAVY TRUCK DYNAMIC ROLLOVER: EFFECT OF LOAD DISTRIBUTION, CARGO TYPE, AND ROAD DESIGN CHARACTERISTICS

The dynamic response of a five-axle tractor–trailer unit carrying loads of various weights was evaluated under actual operating conditions as the vehicle traveled along roadway curves with various radii. A data acquisition system (DAS) was designed and developed to record information for a vehicle moving at highway speeds. The DAS used sensors interfaced to a central processing unit. The test runs were performed over a total of 1,110 km of highway under three load configurations: empty, loaded with less than the truck load, and loaded with bottled spring water packed in boxes. Data on lateral, longitudinal, and vertical accelerations; steering activity; vehicle speed; and roll angle of the trailer were recorded. It was found that in most cases the average level of lateral acceleration exhibited on both the tractor and the trailer exceeded expected values calculated for the curves on the basis of geometric design characteristics. Comparisons of actual results with theoretical considerations confirmed this observation. Analyses of field data indicated that under certain motion and load conditions, the occasional peak lateral acceleration values generated were in the vicinity of rollover threshold values estimated for the instrumented vehicle. The results also showed that although the vehicle traveled at or below the posted speed limit in the majority of cases, lateral accelerations recorded for the trailer exceeded expected lateral accelerations under all load configurations. This suggests the need to consider establishing speed limits on curves that take into consideration the different responses of heavy trucks compared with those of smaller and lighter vehicles.

Impact of Wind Forces on Heavy Truck Stability

A transport truck equipped with instrumentation that measured speed, lateral acceleration, and roll angle of the vehicle was driven around a highway ramp in New Brunswick, Canada, under varying wind conditions. The rollover threshold of the truck was calculated on the basis of characteristics of the vehicle and then compared with the lateral accelerations measured on the truck. Analysis of the data indicated that there was a significant difference in lateral accelerations between different wind speeds, verifying that wind can contribute to rollover. Analysis of the rollover threshold revealed that the lateral accelerations experienced by the truck were often greater than the rollover threshold for brief periods of time, but they were not sufficiently long enough to cause rollover.

Development and Intermediate Findings of a Level III Heavy-Truck Collision Study

The development, implementation, and intermediate results of a Level III (on-scene) study of heavy freight vehicle collisions are presented. The University of New Brunswick’s Accident Research Team, under contract with Transport Canada, has conducted over 50 in-depth investigations over a 3-year period. Although the present findings are based on a relatively small sample, a number of common, and perhaps surprising issues have been identified. Many of the cases highlight the need for increased safety regulations targeted at the design and operation of these vehicles and the infrastructure over which they operate. The most common problems identified include the propensity of heavy trucks to roll over, load security, and inadequate crash protection afforded to the occupant compartment. The issues related to the establishment of an intense investigation protocol are discussed in this paper, as are the findings of the investigations that have occurred over a 3-year period. Recommendations are presented that are directed toward the refinement of a Level III protocol for further heavy-vehicle investigations. In addition, changes are proposed to existing Canadian Motor Vehicle Safety Standards as they apply to heavy trucks.

REGIONAL INTERMODAL FREIGHT TRANSPORT FLOWS AND PROJECTIONS

This study examined intermodal transport in the Province of New Brunswick in Canada’s Maritime Provinces. In 1998, the Policy Branch of the New Brunswick Department of Transportation commissioned the University of New Brunswick’s Transportation Group to conduct a study of intermodal freight transport in New Brunswick. The objective was to evaluate intermodal movements and provide the first provincial database on intermodal traffic, consisting of (a) traffic flowing through the province without an intermediate stop, (b) movements entirely within the province, and (c) movements with either a destination or an origin in the province. Data were collected from rail, truck, air, and marine centers. Transborder (between the United States and Canada) traffic was monitored, and a survey was conducted of shippers using either intermodal transport or potential users of the service. Issues that carriers and shippers had with existing intermodal services were solicited and evaluated. Growth trends for intermodal transport in the study area were developed using a most likely scenario. In developing the growth trends, the potential effects of recent and current events on growth were evaluated.

Safety implications of extending some Canadian Motor Vehicle Safety Standards to light trucks and vans

The primary objective of this research was to evaluate the implications of extending specific Canadian Motor Vehicle Safety Standards (CMVSS) to light trucks and vans (LTVs). This was accomplished through the examination of the potential safety-related benefits of these standards comparing the injury frequencies and severities of the light trucks and vans and the passenger cars (PCs). The standards considered, which currently apply to passenger cars but not to LTVs, are the head restraint (CMVSS 202), side door strength (CMVSS 214), and roof crush strength (CMVSS 216) standards. The comparison was effected by means of logit models developed from multidimensional tables with injury frequency and severity as dependent variables. There are indications that installing head restraints in light trucks and vans could reduce or prevent minor neck injuries and that modest benefits could be achieved by extending the roof crush standard to the LTVs. It was also determined that the side door strength standard may not necessarily be as beneficial to LTVs in conditions in which the vehicle is struck on the side by another LTV. It is suggested that the general public be made aware of the differences in safety standards between LTVs and PCs.

ON THE USE OF MATHEMATICAL PROGRAMMING IN THE EVALUATION OF TRANSPORT POLICIES

This paper focuses on the evaluation processes by which decisions regarding transportation alternatives can be assisted. A multidimensional approach usually called multiple criteria decision making is required to represent the complexity of transportation policy and systems. The multiple criteria decision making techniques can be divided into two groups. The first is based on a ranking scheme approach and the second on a mathematical programming approach. A multiple objective mathematical programming procedure known as Goal Programming is presented. The authors examined the use of that procedure in real transportation problems. The results suggest that multiple objective mathematical programming techniques in general do not appear to be appropriate in transportation policy analysis involving mutually exclusive alternatives. Their use can be limited to special cases in the private sector.