Car Assessment Program Research Articles

NCAP Test Improvements with Pretensioners and Load Limiters

New Car Assessment Program (NCAP) test scores, measured by the United States Department of Transportation's (USDOT) National Highway Traffic Safety Administration (NHTSA), were analyzed in order to assess the benefits of equipping safety belt systems with pretensioners and load limiters. Safety belt pretensioners retract the safety belt almost instantly in a crash to remove excess slack. They tie the occupant to the vehicle's deceleration early during the crash, reducing the peak load experienced by the occupant. Load limiters and other energy management systems allow safety belts to yield in a crash, preventing the shoulder belt from directing too much energy on the chest of the occupant. In NCAP tests, vehicles are crashed into a fixed barrier at 35 mph. During the test, instruments measure the accelerations of the head and chest, as well as the force on the legs of anthropomorphic dummies secured in the vehicle by safety belts. NCAP data from model year 1998 through 2001 cars and light trucks were examined. The combination of pretensioners and load limiters is estimated to reduce Head Injury Criterion (HIC) by 232, chest acceleration by an average of 6.6 g's, and chest deflection (displacement) by 10.6 mm, for drivers and right front passengers. The unit used to measure chest acceleration (g) is defined as a unit of force equal to the force exerted by gravity. All of these reductions are statistically significant. When looked at individually, pretensioners are more effective in reducing HIC scores for both drivers and right front passengers, as well as chest acceleration and chest deflection scores for drivers. Load limiters show greater reductions in chest acceleration and chest deflection scores for right front passengers. By contrast, in make-models for which neither load limiters nor pretensioners have been added, there is little change during 1998 to 2001 in HIC, chest acceleration, or chest deflection values in NCAP tests.

An advanced methodology for estimating vehicle rollover propensity

In the USA light vehicle rollovers represent about 2% of the total vehicle crashes. However, rollovers kill significant numbers of people each year. It is the second most fatal crash mode following frontal crashes. More people in the USA are killed by rollovers than side impacts. The low percentage of occurrences and high rate of fatalities makes rollover the most fatal of all possible crash modes. The National Highway Transport Safety Administration (NHTSA) has been consistently exploring the issues relating to rollover. NHTSA have implemented a star rating system to inform consumers of the rollover propensity of vehicles as part of the New Car Assessment Program. The NHTSA propensity rating is based on the Stability Factor. Recent work by Monash University Accident Research Centre (MUARC) for the Victorian Police Force resulted in range of vehicle functional performance criteria being developed. A criterion relating handling and Stability Factor is proposed. There is sufficient evidence to support the contention that Stability Factor and the rate of ȁreal world rolloversȁ is linked. It is the contention of the authors that the ȁnoiseȁ (scatter) within the Stability Factor data is due to vehicle handling. This paper proposes a methodology that allows the combination of the Stability Factor and handling characteristic to predict the probability of rollover per single vehicle crash.

How Do Euro NCAP Results Correlate with Real-Life Injury Risks? A Paired Comparison Study of Car-to-Car Crashes

The European New Car Assessment Program (Euro NCAP) is a resource for consumers regarding vehicle crash safety. The program promotes safety developments, and credits car manufacturers for focusing on safety. This study was based on real-life car-to-car crashes and results show that the overall indication of the safety level, provided by the Euro NCAP crash testing, is a valid prediction when considering severe or fatal injuries. No significant injury risk differences were seen for minor injury crashes. In car-to-car collisions, cars with three or four stars were found to be approximately 30% safer when compared with two-star cars or cars without a Euro NCAP score. The strong correlation between injury risk and Euro NCAP scores is not necessarily similarly good for individual car models. Pedestrian safety and child occupant protection were not considered in the present study.

Predicting injury risk with “New Car Assessment Program” crashworthiness ratings

The relationship between crashworthiness ratings produced by the National Highway Traffic Safety Administration's (NHTSA's) New Car Assessment Program (NCAP) and the risk of incapacitating injury or death for drivers who are involved in single-car, fixed-object, frontal collisions was examined. The results are based on 6,405 such crashes from the Motor Vehicle Traffic Accident file of the Texas Department of Highways and Public Transportation. The risk of injury was modeled using logistic regression taking into account the NCAP test results for each individual model of car and the intervening effects of car mass, age of the driver, restraint use, and crash severity. Three measures of anthropometric dummy response, Head Injury Criterion (HIC), Chest Deceleration (CD), and femur load were used to indicate vehicle crash test performance. The results show that there is a significant relationship between the results of the NCAP tests and the risk of serious injury or death in actual single-car frontal accidents. In terms of overall injury, chest deceleration was a better predictor than the Head Injury Criterion. For restrained drivers, crash severity, driver age, and chest deceleration were significant parameters for predicting risk of serious injury or death; the risk of injury decreased as chest deceleration decreased. The results were similar for unrestrained drivers although vehicle mass and femur load were also significant factors in the model. The risk of overall injury decreased as chest deceleration decreased but appeared to decrease as femur load increased.