How safe is that new (or used) vehicle? While you might think the answer should be straightforward, experts typically advocate reviewing a range of test results. But which test results give the best information?
Today’s passenger vehicle is typically designed to absorb the excess energy from a collision through its body and deflect it away from the passenger compartment. The U.S. Department of Transportation’s NHTSA (National Highway Traffic Safety Administration) has developed a five-star rating system based on crash tests of new vehicles to assess driver and passenger protection in front- and side-impact crashes. For NHTSA’s frontal-impact test, a vehicle moving at 35 mph (56 km/h) is crashed into a fixed barrier to simulate a head-on collision between two identical vehicles.
In NHTSA’s crash tests, data from two crash dummies buckled into the driver and front-passenger positions are used to assess a belted passenger’s chance of incurring a serious injury in this type of collision. The crash-tested vehicle is assigned from one to five stars to reflect the likelihood of incurring serious injury, i.e., one that could be life-threatening and would require immediate hospitalization, as the result of this type of a collision. Ratings can only be compared between vehicles in the same weight class.
In what some believe may be a more realistic representation of real-world crashes, the force of the crash is shifted to one side of a vehicle’s front end in the Insurance Institute for Highway Safety's (IIHS’) 40-mph (64-km/h) frontal offset crash test. In the 40% offset test, vehicles are assessed for crashworthiness by hitting one side (40% of the vehicle’s full front width) of the vehicle against a barrier moving at 40 mph. The front end of the struck side tends to crush more than in the full-width test, and intrusion into the passenger compartment is more likely. Three factors are evaluated: structural performance, injury measurements, and restraint kinematics.
The structural performance aspect of the IIHS 40% offset test measures the amount of crash-induced movement at 10 standard positions within the vehicle’s passenger compartment. These measurements, which also include the reduction of distance between the A- and B-pillars, help to quantify the amount and pattern of intrusion into the occupant compartment. According to the IIHS, the frontal offset crash tests, which it has been conducting since 1995, have prompted significant improvements in how vehicles protect people in frontal crashes. As with NHTSA’s full-frontal test, these results can be compared only among vehicles of similar weight.
The European New Car Assessment Programme (Euro NCAP) frontal-impact test is similar to the IIHS offset test, as the collision impacts 40% of the width of the widest part of the vehicle being tested. In the Euro NCAP test, developed by the European Enhanced Vehicle-safety Committee, a vehicle traveling at 64 km/h strikes a stationary barrier with a deformable aluminum honeycomb face. The test is designed to simulate a frontal impact of approximately one-half the vehicle’s width with another car of similar mass, each traveling at approximately 55 km/h (34 mph). According to the committee, this is one of Europe’s most frequent types of road crashes resulting in serious or fatal injury.
Side-impact testing assesses a vehicle’s ability to protect its occupants when struck from the side. In the IIHS side-impact test, a stationary vehicle is impacted from the side by a barrier moving at 31 mph (50 km/h); the barrier is designed to simulate impact from the front end of a pickup or SUV. Data retrieved from two crash dummies (one in the front seat and one in the back) are used to assess the effectiveness of head protection measures as well as the likelihood of serious injury to various parts of the body. Structural performance is evaluated based on measurements of B-pillar intrusion into the passenger compartment.
In NHTSA’s side-crash test, a standing vehicle is impacted from the side by a 3015-lb (1368-kg) barrier moving at 38.5 mph (62 km/h) to simulate an intersection-type collision. Data collected from the belted crash dummies are used to assess the likelihood of a life-threatening chest injury in this type of collision. Side-impact test results—both IIHS and NHTSA—can be compared between vehicles, regardless of the vehicles’ weight classes.
In the Euro NCAP side-impact test, a mobile deformable barrier traveling at 50 km/h impacts the vehicle’s driver-side door. Injury protection is assessed using measurements from a crash test dummy in the driver’s seat.
While the NHTSA and Euro NCAP test results tend to focus on the likelihood of serious injury to a vehicle’s occupants under certain types of crash situations, the IIHS test results also incorporate assessment of the vehicle’s structural performance. So which ratings are more important? The intelligent vehicle buyer would probably check both.