Examining potential factors affecting the safety performance and design of exclusive truck facilities

ID: 321 It is believed that increasing truck volumes contribute to traffic congestion, pavement deterioration and crashes due to differences in the physical and operational characteristics of trucks and passenger cars. A 2002 US DOT report showed that the number of crashes involving commercial trucks had increased by 40.3% over the last two decades. Based on Insurance Institute for Highway Safety statistics, trucks represent eleven to thirteen percent of all crash fatalities, while they make up only three percent of all registered vehicles. Also, in two-vehicle crashes involving a truck and a passenger car, it is observed that 98 percent of the fatalities involve occupants of the passenger car. Many state agencies are considering exclusive truck facilities to be an alternative to handle these safety and operational issues due to the increasing truck volumes. There have been many research efforts to understand the relationship between risk factors related to truck traffic and crash frequencies, but most have produced contradicting results. This study aims at examining factors that may influence the safety performance of exclusive truck facilities and at providing recommendations for their design. To accomplish this objective, five years’ roadway and crash data for Texas was collected to develop a comprehensive crash database. Negative binomial regression models were used to establish a relationship between truck crashes and various environmental, geometric and traffic variables. Separate models were developed for truck-related (involving at least one truck and another vehicle), truck-only (two trucks or more) and single-truck crashes. The results suggested that the percentage of trucks in Average Annual Daily Traffic (AADT), classification of the roadway (Rural/Urban), posted speed limit, surface condition, alignment and shoulder width are associated with truck crashes. It is observed that truck-related and truck-only crashes decreased as the percentage of trucks increase on freeway facilities. Based on conclusions derived from the literature review and statistical analyses, straight segments with wider shoulders and uniform grades are recommended for exclusive truck facilities. It is also recommended to provide ramps, horizontal and vertical curvature and signing based on truck size, driver eye height, braking ability and maneuverability. 1 Corresponding and presenting author