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Sharpen Your Skill
NHTSA FAQs

Presented below are some really good answers to many of the questions we simply do not have time to research or ask...

Can I compare vehicles from different classes?

Depending on the weight of a vehicle, it can be compared to other vehicles in it's class. Since a frontal crash test into a fixed barrier is similar to a crash between two vehicles of the same weight, the frontal crash test results can only be compared to other vehicles in the same weight class and those plus or minus 250 lbs.

Side crash test results can be compared across all classes because all vehicles are hit with the same barrier and at the same force.

Rollover Resistance Ratings can also be compared across all classes.

What is the difference between a full frontal test and an offset crash test? Does NHTSA do both?

NHTSA's NCAP Program crashes the full width of the front of a vehicle into a rigid barrier. This maximizes the energy absorbed by the front of the vehicle so that the occupant compartment is more likely to remain intact. The full frontal tests produce high level occupant compartment decelerations, making them very demanding of the restraint systems, thus providing better information on the safety features and their performance.

In offset crash tests, like those performed by the Insurance Institute of Highway Safety (IIHS), only one side of a vehicle's front end is hit, thus a smaller area of the structure absorbs the energy from the crash. Offset crashes are more demanding on the structure of a vehicle, and intrusion into the occupant compartment is more likely in these crashes.

NHTSA is conducting research on offset frontal crash tests.

How do I get more detailed crash data and rollover measurement data?

An electronic version of vehicle crash test reports from 1999 to present, and details of measurements for rollover ratings can both be downloaded from the DOT docket at http://dms.dot.gov.

To use the system you must input a docket number. Details of measurements for rollover ratings can be found in Docket #8298. All 1999 to present frontal NCAP vehicles can be found at Docket #4962 and all 1999 to present side NCAP vehicles can be found at Docket #3835.

A vehicle and occupant curve for all crash tests can be found in the OCR database. You can access the database through the Research and Development link on NHTSA's home page.

For a fee, all NCAP vehicle reports and films are available from the National Crash Analysis Center. Please contact them at 20101 Academic Way, Ashburn, VA 22011, Tel.(703)726-8226 FAX (703)726-8358.

Crash test results are also available on CompuServe using the GO AUTONET command. NHTSA data are found in each model's "Decision Maker" document.

How do most vehicle rollovers occur?

From its studies of real-world single-vehicle crashes, NHTSA has determined that more than 90% of rollovers occur after a driver runs off of the road (see Figure 3). This does not refer to vehicles trying to negotiate difficult trails away from public roads. It refers to vehicles rolling over off of the pavement after the driver has lost control of the vehicle. Once the vehicle slides off of the pavement, a ditch, soft soil, curb or other tripping mechanism usually initiates the rollover.

How does Electronic Stability Control affect rollover, and what is its relationship to the Rollover Resistance Ratings?

Electronic Stability Control(ESC),which is offered under various trade names, is designed to assist drivers in maintaining control of their vehicles during extreme steering maneuvers. It senses when a vehicle is starting to spin out (oversteer) or plow out (understeer), and it turns the vehicle to the appropriate heading by automatically applying the brake at one or more wheels.

Some systems also automatically slow the vehicle with further brake and throttle intervention.

What makes ESC promising for rollover prevention is the possibility that with its aid many drivers will avoid running off the road and having a single vehicle crash in the first place. However, ESC cannot keep a vehicle on the road if its speed is simply too great for the available traction and the maneuver the driver is attempting, or if road departure is a result of driver inattention. In these cases, a single vehicle crash will happen, and the rollover resistance rating will apply as it does to all vehicles in the event of a single vehicle crash.

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