Abstract:
Braking distance of a vehicle is an important safety consideration in highway geometric design.
Braking distances have been commonly estimated based on vehicle wheel loads and assumed tirepavement
friction. The use of classic vehicle dynamics simulation model, which simplifies tire
stiffness as linear elastic function, is a main approach to estimate tire-pavement friction and predict
braking distances. The interaction of nonlinear vehicle dynamics with pavement surface roughness
has not been considered in analyzing its impact on vehicle braking distance. The impact of pavement
roughness induced vehicle vibration on braking distance is the topic of interest in this paper. A
nonlinear vehicle dynamics simulation model is proposed where tire stiffness is considered as a
nonlinear elastic function in the analysis of vehicle dynamics. The model is implemented in
MATLAB 11.0. A hypothetical example is given to illustrate the possible difference between models
with linear and nonlinear tire stiffness in calculating braking distance on a wet pavement. Although
the model presented is rather simplified considering only nonlinear tire stiffness, and a more elaborate
simulation model is required to examine in detail the actual impact of considering nonlinear vehicle
dynamics, the example does show that further study is necessary to examine the need for vehicle
dynamics simulation in order to reliably predict vehicle braking distances on highways, taking into
account the effect of pavement roughness.
