Offtracking is the term used to describe the difference in path radii between the leading and trailing axle of a vehicle as it manoeuvres around a turn. This phenomenon probably has been observed from the time multi-axle vehicles first were constructed. Much of present offtracking analysis is based upon a "zero-speed" assumption. In other words, the magnitude of offtracking is computed simply as a kinematic problem, with no dynamic effects considered. When the problem is analysed kinetically, offtracking outside the path of the preceding wheels (a king of "oversteer") can be computed, depending on vehicle speed and configuration. Effects of roadway superelevation and other three-dimensional terrain features can be included in computer simulations. This paper summarises the history of offtracking analysis, presents a review of calculation methods in the literature, and details the speed-dependent nature of offtracking for two articulated heavy trucks, utilising three-dimensional computer simulation. (A)
Abstract