Search Results

In past years, considerable research has been devoted to occupant response in a variety of low-velocity, bumper-to-bumper impacts. In many crashes, however, the involvement of a braking vehicle or a higher ground clearance vehicle results in an override/underride type crash. The amount of vehicle damage can be significantly greater during such an impact because of the involvement of non-structural components above and below the bumper systems of the involved vehicles. Ten tests were conducted using five target vehicles, each occupied by an instrumented female driver. Each vehicle was tested in a bumper-to-bumper impact and then an override/underride configuration in increasing severity. An independent body shop estimator was employed to document the damage and prepare repair estimates for each test. In each test the vehicle and occupant accelerations were monitored.

Vehicle change in velocity is recognized as one of the most influential parameters on occupant kinematics and injury potential in motor vehicle collisions. Basic engineering principals and some recent epidemiological research indicate the characteristics of the vehicle velocity change, such as the shape and duration of the acceleration vs. time pulse, may also be important. Automotive bumper designs could be enhanced by recognizing these characteristics to potentially influence occupant kinematics and Whiplash Associated Disorders (WAD) in low speed rear impacts. Low speed rear impacts were conducted with a Delta V of 11 km/h using the BioRID P3 anthropomorphic test device. Nominal pulse durations of 80, 100, 140 and 180 msec were tested by varying the dimensions of a foam interface between the impacting pendulum and the rear surface of the test vehicle.

Interest in the mitigation of whiplash associated disorders (WAD) has increased in priority over the last 10 years, and an increasing number of human subject rear-end collision tests have been conducted to assist in the understanding of WAD. Traditionally this testing has examined the effects of variations in occupant characteristics (age, height, gender, etc.), seat characteristics (geometrical and constitutive), and impact severity. This data has resulted in advancements in the understanding of WAD and has provided occupant performance corridors at specific velocity changes, however no controlled study has examined the singular effect of incremental velocity change increases on occupant kinematics. Moreover, while vehicle velocity change is typically employed as a singular measure of impact severity, it is of interest to examine whether this or other impact-related parameters, such as energy or acceleration, are also correlated with occupant kinematics.

A coordinated test and analysis program was conducted to determine whether a previously proposed, linear, analytical model could be adapted to simulate low speed impacts for vehicles with various combinations of energy absorbing bumpers (EAB). The types of bumper systems impacting one another in our program included, in various combinations; foam, piston and honeycomb systems. Impact speeds varied between 4.2 and 14.4 km/h (2.6 and 9.0 mph) and a total of 16 tests in 6 different combinations were conducted. The results of this study reveal that vehicle accelerations vary approximately linearly with impact velocity for a wide variety of bumper systems and that a linear mass-spring-damping model may be used to efficiently model each vehicle/bumper-system for low speed impacts.

The persistent use of an absolute “impact speed” to characterize the “severity” of a collision rather than using the change in velocity (ΔV) or change of kinetic energy (ΔE) suggests persistent misconceptions among both technical and lay people regarding the relationship between those terms and other speed and energy measures in traffic collisions. Through a review of first principles, supported by data from a set of crash tests designed to address the issues raised herein, this paper examines the relationship of the closing or relative velocity to “impact speed,” a speed (or velocity) across the ground (absolute speed) as the indicator of the extent of damage and the potential for injury in a given collision.

Considerable research has been conducted over the past decade on the response of both vehicles and occupants to low speed rear impacts. This research has employed various conditions of target vehicle braking and target occupant awareness. Relatively little effort has been devoted to quantitatively comparing vehicle and occupant responses under different braking and awareness. Given the variety of potential braking and awareness conditions in actual rear impacts, it is desirable to better understand the influence of these reactions on both vehicle and occupant dynamics. Low speed vehicle-to-vehicle rear end collisions were conducted with instrumented vehicles and an instrumented human subject. Six conditions were evaluated: 1) unaware occupant without braking, 2) aware occupant without braking 3) unaware occupant braking “normally”, 4) aware occupant full-braking, 5) unaware occupant with brakes mechanically fully applied, and 6) aware occupant with brakes mechanically fully applied.

Research into the biomechanics of low speed rear impacts has focused primarily on the kinematic responses of anthropometric dummies and human subjects. Occupant muscular activity during low speed rear impacts remains largely unquantified however. The current study enhances the existing database of human subject test exposures with an emphasis on electromyographic activity before, during, and after low speed rear impact. This information may provide insight into injury mechanisms, occupant mathematical modeling, and aspects of seat and head restraint design. Low speed rear impacts using instrumented human subjects were conducted. Ten nominal 16 km/h closing speed car-to-car impacts were conducted using male and female subjects aged 22-54 years, with struck vehicle velocity changes of up to 10 km/h. Two head restraint conditions were studied. One was a standard seat integrated head restraint.

Human volunteer kinematic response to low speed rear-end collisions was investigated. Nominal 16 kph (10 mph) car-to-car impacts were conducted, using human volunteers and anthropomorphic dummies. The human volunteers were both male and female, aged 27 to 58 years, with various degrees of cervical and lumbar spinal degeneration (documented by MRI scan) at the time of the tests. Human volunteer response was monitored and analyzed via accelerometers and high speed film. The impacts resulted in no injury to any of the human volunteers, and no objective changes in the condition of their cervical or lumbar spines. The results indicate a minimum injury tolerance to low speed rear-end impacts for males and females with various degrees of spinal degeneration. Kinematic responses of the head, mandible, upper torso and knees are discussed in light of existing theories regarding injury causation and tolerance.

Low speed crash tests with Ford Escorts of model years 1981-1983 were conducted. The response of these vehicles equipped with energy absorbing bumpers in bumper-to-bumper impacts and in an under-ride of one bumper under another are evaluated. Bumper displacement, vehicle acceleration, and vehicle velocity time histories are presented for both bullet and target vehicles. Two impacts each at 2.23, 4.47, and 6.71 m/s were conducted. Similar data is presented for a 4.47 m/s impact in which the front bumper of the bullet vehicle underrode the rear bumper of the target vehicle. Results indicate increased damage associated with the underride test, without corresponding increases in vehicle responses.