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The passenger car tire testing reported herein extends earlier published research. Results under minimally-wet conditions displayed behavior similar to those previous tests conducted at greater water depths, except for the lowest water depth considered (0.25 mm or 0.01 inches). These tests reinforce the earlier conclusion that tire tread depths of less than about 3.0 mm (4/32 inches) develop significantly less cornering friction on wet surfaces at highway speeds than will tires of greater tread depth, and can approach hydroplaning at those speeds in the presence of minimal water film thickness. Some effects on wet friction capability due to tire aging and aspect ratio are presented, as well as some observations on the significance of tire placement. Also presented are suggested methods for relating laboratory results to real-world highways.

An experimental investigation of the minimum mileage between required brake adjustments is presented, for a particular vehicle configuration, fully loaded, on a defined route. To insure the results represented maximum brake lining wear, or minimum adjustment interval, for a container chassis, the operator followed a strict protocol requiring the use of chassis brakes only, except when safety dictated otherwise. The data collected during the investigation have been tested against a proposed procedure for predicting brake adjustment frequency. This procedure should allow brake adjustment intervals to be predicted for other vehicle configurations and other service conditions.

Tractor-trailer rollover due to high crosswinds is a well-recognized accident type. Some highway jurisdictions limit high-profile vehicle travel under certain weather conditions in certain locations to reduce the probability of rollover or other loss of control. The criteria for these travel limitations appear to be based upon analyses of very simple vehicle models. The present paper examines the rollover potential of tractor-trailers in high crosswinds utilizing a sophisticated dynamic multi-mass vehicle model. This model was developed to study handling and collisions and includes the capability to account for aerodynamic forces.

When an automobile is driven on wet roads, its tires must remove water from between the tread and road surfaces. It is well known that the ability of a tire to remove water depends heavily on tread depth, water depth and speed, as well as other factors, such as tire load, air pressure and tread design. It is less well known that tire tread depth combined with placement can have an adverse effect on vehicle handling on wet roads. This paper investigates passenger car handling on wet roads. Flat bed tire testing, three-dimensional computer simulation and skid pad experimental testing are used to determine how handling is affected by tire tread depth and front/rear position of low-tread-depth tires on the vehicle. Some skid pad test results are given, along with corresponding simulations. A literature review also is presented. Significant changes in tire-road longitudinal and lateral friction are shown to occur as speed, tread depth and water depth vary, even before hydroplaning occurs.

Offtracking is the term used to describe the difference in path radii between the leading and trailing axle of a vehicle as it maneuvers around a turn. This phenomenon probably has been observed from the time multi-axle vehicles first were constructed. As vehicles, particularly articulated trucks, have become larger and longer, and the urban environment has become more compact and crowded, practical safety concerns relating to offtracking have increased. The geometric design of streets and highways, and of parking lots and trucking yards, will be affected by the maximum offtracking of vehicles using those facilities. In some accident investigations, offtracking is a primary consideration. 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.