Motor vehicle crashes are complex events resulting from several factors, including driver behavior, the driving environment, and the vehicle. Vehicle design can affect safety through crashworthiness—that is, by providing occupants protection during a crash—and through crash avoidance—that is, by helping the driver to avoid a crash or recover from a driving error. Vehicle characteristics such as size, weight, and the type of restraint system affect crashworthiness because they play a large role in determining the likelihood and extent of occupant injury from a crash. Vehicle characteristics such as vehicle stability and braking performance are examples of crash avoidance features in that they aid the driver in preventing a crash from occurring. The New Car Assessment Program (NCAP) was established in response to a requirement in the Motor Vehicle Information and Cost Savings Act of 1972 to provide consumers with a measure of the relative crashworthiness of passenger vehicles. NCAP’s goals are to improve occupant safety by providing market incentives for vehicle manufacturers to voluntarily design vehicles with improved crashworthiness and provide independent safety information to aid consumers in making comparative vehicle purchase decisions. NHTSA has pursued these goals by conducting frontal and side crash tests and a rollover test, assigning star ratings, and reporting the results to the public. In fiscal year 2004, NCAP conducted 85 crash tests and 36 rollover tests, with a budget of $7.7 million. NHTSA also administers the Federal Motor Vehicle Safety Standards. All motor vehicles sold in the United States for use on the nation’s highways must meet minimum safety requirements as required by the standards. The standards prescribe a minimum performance level for crashworthiness that vehicles must meet in a number of different crash tests. Auto manufacturers self-certify that their vehicles meet these minimum standards. To test compliance with some of these standards, NHTSA conducts 30 miles per hour (mph) frontal impact tests and 33.5 mph side impact tests for belted occupants. The Federal Motor Vehicle Safety Standards tests serve as a foundation for NCAP testing. The test protocols for NCAP’s frontal and side crash tests are the same as the safety standards, except that the NCAP tests are conducted at 5 mph faster. NHTSA’s policy, although not required by law, has been to make changes to the safety standards before considering changes to NCAP. When considering changes to NCAP, NHTSA generally follows the informal rulemaking process, which includes seeking comments on proposed changes. NCAP provides consumers with information regarding the crashworthiness of new cars beyond the applicable Federal Motor Vehicle Safety Standards with which all vehicles sold in the United States must comply. There are no minimum performance levels for the NCAP tests. NHTSA tests as many vehicles as possible under NCAP to provide consumers with sufficient independent information to make vehicle comparisons. In contrast, NHTSA relies on auto manufacturers to self-certify compliance with the Federal Motor Vehicle Safety Standards and only conducts a limited number of tests to ensure manufacturer compliance. NHTSA conducted the first NCAP crash tests in 1978 on model year 1979 vehicles, measuring only the crashworthiness of passenger cars in frontal crashes. Since then, there have been a number of vehicle tests added to NCAP, as shown in figure 3. For model year 1983, NHTSA expanded NCAP to include light trucks, vans, and SUVs. In 1996, NHTSA first began the side-impact NCAP test for model year 1997 vehicles. NHTSA expanded the side-impact NCAP test to include light trucks, vans, and SUVs for model year 1999. NHTSA began to rate vehicles for their rollover risk beginning with the 2001 model year. NHTSA initially rated the risk of vehicle rollover by measuring the top-heaviness of a vehicle and comparing this measurement to the top-heaviness of vehicles involved in single-vehicle crashes, as reflected in crash data. As required by the November 2000 Transportation, Recall Enhancement, Accountability and Documentation (TREAD) Act, NHTSA began dynamic rollover testing on model year 2004 vehicles to supplement the measurement of a vehicle’s top-heaviness in determining a vehicle’s rollover risk. NHTSA conducts three types of tests in NCAP: a full frontal crash test, an angled side crash test, and a rollover test. NCAP ratings, designed to aid consumers in deciding which vehicle to purchase, are available to the public on the Internet and through NHTSA’s Buying a Safer Car brochure. NCAP crash results are also used in developing vehicle safety ratings by other organizations, such as Consumer Reports and The Car Book. Every year NHTSA tests new vehicles that are predicted to have high sales volume, have been redesigned with structural changes, or have improved safety equipment. NHTSA purchases vehicles—the base model with standard equipment—for frontal and side crash tests directly from dealerships across the country, just as the consumer would. The vehicles are provided to five contractors that conduct the crash tests. NCAP crash- test ratings only apply to belted occupants, as the crash test dummies used in NCAP tests are secured with the vehicle’s safety belts. According to NHTSA officials, NCAP crash-test ratings are available on about 85 percent of the new vehicles sold because ratings for some models that have had no significant safety or structural changes are carried over from year to year. For the rollover tests, which are nondestructive, NHTSA leases new vehicles, which are tested at one contractor location. Rollover risk ratings are available for about 75 percent of new vehicles sold, according to NHTSA officials. The full frontal crash test is the equivalent of two identical vehicles, both traveling at 35 mph, crashing into each other head-on. The test vehicle is attached to a cable and towed along a track at 35 mph so that the entire front end of the vehicle engages a fixed rigid barrier, as shown in figure 4. This type of crash test produces high level occupant deceleration, making this test demanding of the vehicle’s restraint system. Click the following link to watch a video of a full frontal crash test conducted by NHTSA NCAP at 35 mph: http://www.gao.gov/media/video/d05370v1.mpg Because the full frontal crash test is equivalent to two identical vehicles moving toward each other at 35 mph, the crash test results can only be compared to other vehicles in the same class and with a weight that is plus or minus 250 pounds of the test vehicle. The test protocols for the full frontal NCAP test are the same as the full frontal belted test in the Federal Motor Vehicle Safety Standards, with the exception of the test speed—the NCAP test is conducted at 35 mph, 5 mph faster than the standard test. The angled side crash test simulates an intersection collision in which one moving vehicle strikes another moving vehicle. The test vehicle is positioned such that the driver’s side forms a 63 degree angle with the test track. On the other end of the test track is a chassis with a barrier also turned at a 63 degree angle. The barrier is made of a deformable material to replicate the front of another vehicle and is attached to a cable that tows it down a track into the test vehicle at 38.5 mph. Both the barrier face and the driver’s side of the vehicle are parallel, so that the entire face of the barrier impacts the side of the vehicle, as shown in figure 5. Click the following link to watch a video of an angled side crash test conducted by NHTSA NCAP at 38.5 mph: http://www.gao.gov/media/video/d05370v2.mpg Because all vehicles are hit with the same force by the same moving barrier, test results can be compared across weight classes. The barrier used in this test weighs approximately 3,015 pounds, and the top of the deformable face is approximately 32 inches from the ground. The side NCAP test is similar to the Federal Motor Vehicle Safety Standards test, with the exception that the side NCAP test is conducted at 38.5 mph, or 5 mph faster than the safety standard test. The dynamic rollover test simulates a driver making a high-speed collision avoidance maneuver—steering sharply in one direction, then sharply in the other direction—within about 1 second. NHTSA has focused its rollover test primarily on pickups and SUVs because cars are not susceptible to tipping up in this test. The rollover test is actually a series of four runs, two left/right tests and two right/left tests, at two different steering wheel angles and different speeds. Before the test, the vehicle is loaded to represent five passengers and a full tank of gas. During the test, the steering wheel is turned sharply in one direction at a high speed and then turned sharply in the opposite direction at a greater steering angle. The first run of each test is conducted at 35 mph. Subsequent runs are conducted at about 40 mph, 45 mph, 47.5 mph and 50 mph, until the vehicle fails or “tips up” as defined by test procedures or attains a speed of 50 mph on the last run of each test without tipping up. Tipping up is defined as both wheels on one side of the vehicle lifting off the ground more than 2 inches simultaneously, which most commonly occurs during the second turn, as exhibited in figure 6. Outriggers are attached to the vehicle to prevent it from tipping all the way over and injuring the test driver. NHTSA separately rates the frontal, side, and rollover tests. It assigns one (worst) to five (best) stars to communicate the results of the three tests to aid consumers in their vehicle purchase decisions.