Showing papers on "Rollover published in 1989"

Rollover caused by concrete safety-shaped barrier

Abstract: The results of a study sponsored by the Federal Highway Administration and conducted at the Texas Transportation Institute that examined the issue of rollovers caused by concrete safety-shaped barriers are presented. The study objectives were to determine the extent and severity of overturn collisions with concrete safety-shaped barriers, identify the causes of rollover of vehicles in impacts with concrete safety-shaped barriers, and identify potential countermeasures to reduce concrete safety-shaped barrier rollovers. The study approach consisted of a critical review of the literature, clinical and statistical analysis of accident data files, and computer simulation. The extent of the rollover problem on concrete safety-shaped barriers was found to be less than reported in previous literature. A number of impact conditions were identified from accident studies and confirmed by simulation as potential contributory factors to rollovers. Three alternative barrier shapes were evaluated as potential countermeasures: F-shape, constant slope, and vertical wall. Results of the evaluation indicate that the F-shaped barrier offers little performance improvement over the existing safety shape. The vertical wall barrier offers the greatest reduction in rollover potential, but with the greatest increase in lateral accelerations. The constant sloped barrier may provide the best compromise solution.

Kineto-static roll plane analysis of articulated tank vehicles

Abstract: The roll stability of an articulated tank vehicle with partial liquid load is discussed from the viewpoint of fundamental mechanics of vehicle response and quantitative influence of size and weight variables. A kineto-static roll plane model for a partially filled tank vehicle of arbitrary tank geometry is developed incorporating the moments and forces associated with liquid movement within the tank. A roll plane model for a partially filled tank of arbitrary shape is developed and integrated with the static roll plane model of the vehicle. The influence of liquid motion within the tank during a steady turning manoeuvre is investigated. The rollover immunity of the tank vehicle is investigated through computer simulation. The vertical and lateral translation of the fluid bulk during steady turning is computed using an iterative algorithm. The corresponding roll moments and forces arising due to liquid motion are incorporated into the static roll model to study the rollover immunity levels of liquid tank vehicles. The influence of tank geometry and liquid fill level on the rollover immunity of the tank vehicles is presented. The rollover threshold levels of the tank vehicle are compared to that of an equivalent rigid cargo vehicle for various loading conditions. The influence of compartmenting of the tank and the influence of the location of the trailer axles on the rollover immunity levels is studied and an optimal order to unloading the various compartments is determined. (Author/TRRL)

Static stability as a predictor of overturn in fatal motor vehicle crashes.

Abstract: Fatal Accident Reporting System (FARS) files for the years 1981-1984 were examined for rollover crash involvement of 15 utility and passenger vehicle make-models for which static stability values (1/2 track width divided by height of center of gravity) were published. The values ranged from highs of 1.57-1.62 for the pre-1979 Ford LTD, the pre-1979 Chevrolet Nova, and the pre-1982 Pontiac Firebird to lows of 1.01-1.07 for the Jeep CJ-5 and CJ-7 and the pre-1978 Ford Bronco. Rollover as the first harmful event and as the most harmful event per 100,000 vehicles registered was strongly predicted by stability. Stability was unrelated to nonrollover crashes. The low-stability vehicles were much more likely to roll over on the road rather than after leaving the road. Other road, driver, and environmental risk factors recorded in the FARS files were not correlated to stability in such a way as to explain the high rollover of low-stability vehicles. Using Federal Highway Administration vehicle mileage estimates, calculations were made of the mileages under various conditions which the vehicles with low stability values would have to have been driven if mileage or hazardous-condition differences rather than stability differences accounted for their substantially higher fatal rollover fatal crash rates. This analysis indicates that fatal rollover rates of low-stability vehicles could not have occurred at reasonable mileage.

Risk of fatal rollover in utility vehicles relative to static stability

Abstract: The risk of fatal rollover of utility vehicles per 100,000 registered vehicles relative to cars during 1982-87 was strongly correlated to the static stability of the vehicles. Distance between the center of the tires divided by twice the height of center of gravity explained 62 per cent of the variation in fatal rollover rates where rollover was the first harmful event. Statistical controls for 20 major risk factors indicated no correlations that would deflate the correlation between stability and rollover. Low stability utility vehicles roll over more often on the road suggesting that the lateral force of turning is often the tipping force.

Rollover potential of vehicles on embankments, sideslopes and other roadside features

Abstract: This study examined vehicle interaction with various roadside features to determine key roadside-feature design criteria based on their potential for inducing vehicle rollover. The Highway-Vehicle Object Simulation Model (HVOSM) computer program was used in the study to determine dfferences between large and small vehicles and their performance capabilities with regard to various roadside features. The HVOSM was modified to improve its application to rollover situations. The results of the study are presented and discussed. The tests showed that 3:1 slopes are only marginally safe for traversal by small, lightweight automobiles. Ditches with front slopes no steeper than 3:1 appear relatively safe. These and other study results are discussed.

Aircraft Crash Survival Design Guide. Volume 3. Aircraft Structural Crash Resistance

Abstract: This five-volume publication has been compiled to assist design engineers in understanding the design considerations associated with the development of crash-resistant U.S. Army aircraft. A collection of available information and data pertinent to aircraft crash resistance is presented, along with suggested design conditions and criteria. The five volumes of the Aircraft Crash Survival Design Guide cover the following topics: Volume 1 - Design Criteria and Checklist; Volume 2 - Aircraft Design Crash Impact Conditions and Human Tolerance; Volume 3 - Aircraft Structural Crash Resistance; Volume 4 - Aircraft Seats, Restraints, Litters and Cockpit/Cabin Delethalization; and Volume 5 - Aircraft Postcrash Survival. This volume (Volume 3) contains information on the design of aircraft structures and structural elements for improved crash survivability. Current requirements for structural design of the U.S. Army aircraft pertaining to crash resistance are discussed. Principles for crash-resistant design are presented in detail for the landing gear and fuselage subject to a range of crash conditions, including impacts that are primarily longitudinal, vertical or lateral in nature and those that involve more complicated dynamic conditions, such as rollover. Analytical methods for evaluating structural crash resistance are described.

Simulations of vehicle dynamics during rollover. final report

Abstract: The capability to predictively simulate vehicle rollover dynamics using the Articulated Total Body (ATB) model was developed and validated using the results of two controlled automobile rollover crash tests. The vehicle was modeled as a single rigid body with vehicle contact surfaces approximated by (hyper)ellipsoids. Appropriate vehicle mass, center of mass, rotational inertial properties, initial conditions, and the interactive geometry between the vehicle and the crash environment were specified. The events simulated were a multiple crash/rollover in which a vehicle was induced to roll by a ramped guardrail and a rollover which was initiated by an active rollover test device developed by the national Highway Traffic Safety Administration. The results of these computer simulations were compared with high-speed film coverage of the tests using computer graphics images of the predicted vehicle positions. Also compared were the linear and angular accelerations, velocities, displacements, and kinetic energies. The simulated results compared well to the test results. Particularly good agreement was achieved for vehicle position in time. Angular velocities also showed good agreement. Poorest agreement was between the simulated and measured vehicle accelerations.

Statistical estimation of rollover risk. final report

Abstract: This report describes the results of a statistical analysis to determine the probability of a rollover in a single vehicle accident. Over 39,000 accidents, which included 4910 rollovers in the states of Texas, Maryland, and Washington were examined for 40 vehicle make/models using logistic regression analyses. Mathematical models were developed that related vehicle factors such as wheelbase and stability factor (one-half the track width divided by the center of gravity height) and accident factors (driver and environmental variables) to rollover probability. It was found that at the accident level (predicting rollover versus nonrollover) the vehicle stability factor and whether the accident occurred on an urban or rural road are important predictors of rollover probability. At the vehicle make/model level (comparison of predicted and actual rollover rates for the 40 make/models), the index of agreement (r-squared) exceeded 0.90 with the stability factor in the regression model. Without the stability factor, the r-squared dropped to 0.53 indicating the importance of this factor. Other factors added little to predicting rollover at the make/model level.

Development and analysis of intermediate tripped vehicle rollover model (itrs). final report

Abstract: This report describes the development of the Intermediate Tripped Rollover Simulation (ITRS) which can be used to investigate the rollover behavior of vehicles impacting a roadside curb. The eight degree-of-freedom ITRS model consists of sprung and unsprung masses interconnected through suspension elements. The ITRS model accounts for complete forward, lateral and directional dynamics and is capable of simulating vehicle skidding motion, simultaneous and oblique impact of the front and rear wheels with a curb, and subsequent tripped rollover under a variety of initial conditions. The ITRS vehicle model has been thoroughly examined for the energy exchanged between the vehicle components. Two energy based rollover functions were developed and examined to assess their ability to predict rollover. It has been shown that, if tripped rollover is to occur at critical speed, the dynamic criteria for rollover become satisfied when vehicle roll angles equal 9.5 and 11.5 degrees for impact angles of 0 and 25 degrees, respectively. The influence of all design parameters on vehicle rollover stability during both side and oblique impacts has been determined using the percentage sensitivity functions. The sensitivity results demonstrate that geometrical, mass and impact deformation characteristics have the largest influence on vehicle rollover propensity in tripped rollover situations.

Rollover caused by concrete safety shaped barrier, volume i - technical report. final report

Abstract: The objectives of this study are to: (1) identify the root causes of rollover of vehicles in impacts with concrete safety shaped barriers, (2) determine the extent and severity of overturn collisions with concrete safety shaped barriers, and (3) identify potential countermeasures to reduce shaped concrete barrier rollovers. The study approach consisted of critical review of literature, statistical and clinical analysis of four accident data files, and computer simulations. The extent of the rollover problem on concrete safety shaped barriers is found to be less than reported in previous literature. A number of impact conditions were identified from accident studies and confirmed by simulation as potential contributory factors to rollovers. Three alternate shapes were evaluated as potential countermeasures: (1) F-shape, (2) single constant sloped barrier, and (3) vertical wall. Results of the evaluation show that the F-shape barrier offers little performance improvement. The vertical wall barrier offers the greatest reduction in rollover potential, but also with the greatest increase in lateral accelerations. The single constant sloped barrier with an 80 degree slope may provide the best compromise solution. A benefit/cost analysis is needed and recommedned to properly compare between the various barrier shapes. This is Volume I of a two-volume final report. The other volume, FHWA-RD-88-220, contains appendixes that are too bulky for inclusion in this technical report. It is only available from the National Technical Information Service.

Reconstruction of motor vehicle accidents: a technical compendium. rollover potential of vehicles on embankments, sideslopes, and other roadside features

Abstract: This paper presents results of a computer simulation analysis to examine the potential of roadside features for inducing vehicle rollover. A modified version of the Highway-Vehicle-Object Simulation Model (HVOSM) incorporating a tire/deformable-soil interaction model was verified by full-scale vehicle tests and used to predict the dynamic responses of representative small and large automobiles traversing various roadside terrain for both tracking and nontracking departures from the roadway.

The dynamic stability testing of articulated vehicles

Abstract: This paper describes a full scale truck testing program designed to investigate the rollover behaviour of articulated vehicles. Test details and equipment including vehicle manoeuvres, anti rollover outrigger, instrumentation and data acquisition system are discussed. Results of suspension and handling characteristics, as well as steady state and dynamic rollover behaviour of vehicle combinations are presented. The steady state rollover threshold of test vehicles obtained from constant radius turn tests is found to be slightly lower than static tilt test results. The main factors that contribute to the discrepancy include the lateral tyre restraint on the tilt deck and the asymmetric rollover behaviour of test vehicles. A good agreement between these two test methods can be obtained by properly accounting for those factors. Under transient conditions, the rollover behaviour of test vehicles is affected by the phase difference in lateral acceleration between the prime mover and the trailer (A).

Roll bar for a vehicle

Abstract: In vehicles that are equipped with a rollover protection device, it may be expedient to design the rollover protection device to be lowerable. This is done by pivoting the upper frame part (30), which is possible from the driver's seat. The upper frame part (30) is connected via an axis of rotation (32) to posts (22) attached to the vehicle. It can be locked by securing bolts (40) both in the upright position and in a tilted position. The upper frame part (30) carries a lever arm (52) with a handle (54). This lever arm (52) enables the upper frame part (30) to be pivoted about the axis of rotation (32) without the driver having to move away from his driver's seat.

Dynamic behavior of seatbelts in rollover situation

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