Showing papers on "Rollover published in 1979"

Simulation of the directional response characteristics of tractor-semitrailer vehicles

Abstract: The report examines the capability of a detailed digital simulation for predicting the response to steering of tractor-semitrailer vehicles in (1) obstacle-avoidance maneuvers, (2) turning near the rollover limit, and (3) steady turning Measured and simulated results are presented for a three-axle tractor combined with either a van-trailer or a flat-bed trailer The influences of changes in tractor frame stiffness and/or the roll stiffness of the front suspension are considered in assessing the validity of the simulation Particular emphasis is placed on investigating the prediction of the articulation angle existing between the tractor and the semitrailer during steady turns The study concludes that the simulation is capable of doing an excellent job of predicting vehicle response in obstacle-avoidance maneuvers

Vehicle downsizing and roadside safety hardware

Abstract: Downsizing of domestic passenger vehicles is expected to be a major element in corporate strategies to meet legislated fuel economy mandates. With the expected introduction of significant numbers of mini-sized automobiles in the vehicle fleet, there is a need to re-examine existing roadside safety hardware design and performance criteria. Current roadside protective device designs and performance criteria are for the most part based on experience with vehicles in the 2,250 to 4,500 lb weight range. An analysis of future vehicle downsizing trends suggests that vehicles as light as 1,700 to 1,800 lb need to be considered. From available research findings it is known that crash severity increases with decreasing vehicle weight in collisions with pole like structures. High speed off center impacts of small cars into such structures may result in violent multiple rollovers. Thus it is important that the safety performance criteria for breakaway signs and luminaire supports, base bending signs, and other poles and supports be re-examined. Vehicle geometry, inertial characteristics and crash properties of mini-sized cars may present special problems in the design of traffic railings. Snagging of support posts and vehicle rollover has been observed in traffic railing tests to date with these small vehicles. Impact attenuators have been designed to accommodate vehicles in the 2,250 to 4,500 lb weight range. The performance criteria for these devises should be re-examined to consider mini-sized car problems. In this paper the evolution of the consideration of vehicle size in roadside safety hardware research is reviewed and the data available to assist in the selection of the initial mini-sized cars of interest are discussed. Results from ongoing research efforts aimed at identifying safety problems in such collisions and developing appropriate countermeasures are reviewed.

Simulation of the directional response characteristics of tractor-semitrailer vehicles: final technical report

Abstract: The capability of a detailed digital simulation is examined for predicting the steering response of tractor-semitrailers in obstacle-avoidance maneuvers, turning near the rollover limit, and steady turning. Measured and simulated results are presented for a three-axle tractor combined with either a van-trailer or a flat-bed trailer. The effect of changes in tractor frame stiffness and/or the roll stiffness of the front suspension is used to assess the validity of the simulation. Particular emphasis is given to the prediction of the articulation angle between the tractor and semitrailer during steady turns. It is concluded that the simulation provides an excellent prediction of vehicle response in obstacle-avoidance maneuvers. It has reasonable predictive capabilities for vehicle performance in severe turning maneuvers approaching the rollover limit. Since vehicle performance is very sensitive to steering level, forward velocity, and vehicle parameters in severe turns, very accurate input and parametric data are needed. Simulation data on trailer oversteer/understeer in steady turning with moderate lateral acceleration do not agree well with measured values. The articulation angle study indicates that further research is needed to obtain a detailed understanding of the steady turning behavior of articulated vehicles.