Lane Change Dynamics of a Commercial Tractor-Trailer
Authors: Boggess Brian M. , Ralston Harold H. , Boyd Dusty A. , Strawbridge Bryan E. , Morr Douglas R. , Dunn Ashley L. , Castro Elaine K. 
Published: January 2020

A number of vehicle-to-vehicle accidents occur as a result of significant differentials in speed and lane changes between traffic in laterally offset lane positions. These analyses can include many scenarios. One typical scenario is the merging of an articulated commercial vehicle from a roadway shoulder or on-ramp into a travel lane at a relatively low speed compared to the posted speed limit and/or actual travel speed of established lane traffic. Collisions arising during such events often involve less than full engagement between the vehicles and are complicated by the extended length (20 meters (m) (65.6 feet (ft)) or more) of most combination units and its effect on the time and distance it takes the unit to transition from one lane to another.

Vehicle dynamics is used to analyze and understand the lane change dynamics in order to assess causes of accidents, as well as aide engineers in creating safeguards to avoid such accidents. A review of currently available analytical models finds that most are based on an analysis of a single-point object or a standard, non-articulated passenger vehicle. Additionally, many of these models consider either a constant lateral acceleration profile or a half-sine acceleration profile with specified peak lateral acceleration resulting in a constant lane change time regardless of vehicle longitudinal speed. When considering the actual lane change dynamics of a tractor-trailer, the typically applied predictive models are limited to predicting the dynamics of a singular point on the tractor-trailer during the lane change as opposed to more specific dynamics of the tractor and trailer combined effect.

Testing in this study was completed using a conventional truck-tractor with sleeper berth, coupled to an unloaded 40-foot trailer chassis with a container. A total of 23 tests were completed, including (a) constant speed maneuvers for travel speeds ranging from 8.0 to 67.6 kilometers per hour (kph) (5.0 to 42.0 miles per hour (mph)) and (b) continuously accelerating travel speeds with lane changes initiated at 10.5 to 27.4 kph (6.5 to 17.0 mph). Two-dimensional time dependent tracking of the corners (tractor front left and right, trailer rear left and right) of the vehicle was documented and an imaging of the Detroit Diesel engine electronic control module (ECM) was collected after each test. Results of this study show that above speed ranges of 48 to 56 kph (30–35 mph), the timing involved in a constant-speed lane change maneuver tends to converge toward a constant; however, at lower speeds a clear inverse relation exists between speed and lane change timing. Empirical relationships were developed to more accurately predict the lane change dynamics of multiple points and the overall profile of an articulated commercial vehicle. Overall, this study provides data and relationships for consideration in lane change dynamics as well as the ability to distinguish timing of when a tractor-trailer would become perceivable versus its position in the roadway.