ABS Education Alliance Newsroom

Response to NHTSA Study

Questions have been raised about the study by the U.S. Department of Transportation's National Highway Traffic Safety Administration (NHTSA) on the effectiveness of anti-lock brake systems. The ABS Education Alliance, a coalition of anti-lock brake manufacturers, had its technical experts review the study and, in fact, found the questions raised to be based on a misunderstanding of the study's results.

NHTSA's report on the preliminary evaluation of anti-lock brakes, completed in December 1994, clearly indicates ABS is effective in reducing crashes. The study found that "involvements in multivehicle crashes on wet roads were significantly reduced in the cars equipped with ABS: fatal crashes were reduced by 24 percent and nonfatal crashes by 14 percent. Fatal collisions with pedestrians and bicyclists were down by a significant 27 percent with ABS."

Both Transportation Secretary Federico Peña and NHTSA Administrator Ricardo Martinez have responded positively to ABS. Peña, during a demonstration of ABS in August, said, "Anti-lock brakes offer an important safety advantage by allowing drivers to steer and maneuver their vehicles during hard braking."

A follow-up study completed by NHTSA in May 1995 found that ABS-equipped cars were involved in fewer crashes than non-ABS cars. This was particularly due to a significant decrease in passenger car crashes that involve frontal impacts or that occur when a car cannot stop in time. Cars equipped with ABS suffered 2,799 fewer crashes than cars without ABS. This number becomes even more significant as it represents 82.4 percent of all the crashes analyzed by NHTSA.

Nonetheless, concerns have been raised about the involvement of ABS-equipped cars in other types of collisions.

The NHTSA report found that cars equipped with ABS had a higher number of crashes that resulted from a vehicle running off the road. Of such crashes, which accounted for 17.6 percent of the crashes analyzed, ABS cars were involved in 236 more incidents than non-ABS cars. Those numbers must be viewed in proper context. With the decrease of 2,799 crashes, ABS cars were still involved in 2,563 fewer crashes than non-ABS cars, for an overall reduction of 11 percent in crashes for ABS-equipped vehicles in any type of driving condition.

Moreover, NHTSA could not determine that ABS was to blame for the increase. Even the initial report stated the agency was "not yet certain that the observed increase is a direct consequence of the ABS system and/or the driver's interaction with ABS." It is possible ABS was not even a factor in all the accidents. Outside factors, such as the change in the national speed limit from 55 miles per hour to 65 miles per hour, may have accounted for an increase in accidents. As the speed of the vehicle increases, the distance required to stop increases at an even faster rate, as does the force of impact in a collision. Drivers involved in collisions may not have allowed for the extra response time.

Other factors may account for accidents as well, according to the 1994 report:

Believing ABS-equipped cars will allow them to stop in a shorter distance or maintain control, drivers may feel emboldened to take more risks than they otherwise would.
Unaware how ABS functions, drivers may pump the brakes in an emergency stopping situation. This defeats the purpose of ABS, which automatically pumps when activated.
When they feel the brake pedals pulsating, which means the ABS is working, drivers may pump or release their brakes.
They may react to an imminent crash threat by abruptly braking and steering. The front wheels of cars without ABS would lock, causing the car to skid straight ahead, but ABS-equipped cars could be steered off the road. Enhanced steering control may mean drivers don't strike vehicles they once would have hit.

The Alliance feels the overall statistical significance of the two sets of data needs further analysis, particularly regarding the representation of the sample. For example, none of the known Snow Belt states were considered in the data base.

Furthermore, the data only examine the negative side of ABS. No data exist to account for the number of "near misses" ABS helped prevent with increased stability, steerability and controllability of vehicles. There is no information to calculate the collisions avoided and the lives saved because a car was equipped with ABS.

QUESTIONS AND ANSWERS

1. What is the safety advantage to ABS?

ABS systems can improve stability and steerability, and, in some cases, can shorten stopping distance during heavy or emergency-type braking on most surfaces by preventing the wheels from locking. A rotating wheel is more stable and allows the driver to effectively brake, steer, maneuver and potentially avoid an impact.
Even with ABS, drivers should always operate their vehicles with the same care and caution as those driving cars with conventional braking systems. As with any car, those driving faster or more aggressively, or maintaining unsafe following distances put themselves and others at risk.
Overall, ABS has a proven ability to improve safety under hazardous driving conditions, particularly on wet and slippery roads. The Alliance members have spent thousands of man-hours over the course of two years for each vehicle platform, performing tens of thousands of tests on each type of car in which ABS is installed -- tests for every driving maneuver on every road surface condition.

2. Why did NHTSA research suggest that ABS vehicles may be more likely than non-ABS vehicles to run off the road, roll over or have a frontal impact with a fixed object?

Vehicles equipped with ABS can respond better when a driver steers while braking, whether the driver is using ABS correctly or incorrectly. In an effort to avoid a collision with an object in the road, a driver may intentionally or unintentionally steer the vehicle off the road. Thus, an off-the-road collision may, in some cases, be looked at as the avoidance of another, more serious frontal collision. Again, off-the-road crashes and roll-overs accounted for only 17.6 percent of crashes in the study.
The 1994 study concluded that "ABS confers the capability to steer a car while slamming on the brakes, but the average driver in a panic situation might not always use this capacity to an advantage, and might even steer the car into a worse situation than the one which the driver was trying to avoid." Impacts with fixed objects and roll-overs are more likely if the vehicle steers off the road onto irregular terrain.
The Alliance's goal is to educate consumers by providing a better understanding of how ABS operates through a national outreach program to drivers. The Alliance members believe the benefits of ABS must be maximized through sound yet simple education on this critical driving system.

3. Why are ABS-equipped vehicles more likely to be struck from the rear than non-ABS equipped vehicles?

When braking from the same speed on the same surface, especially wet paved surfaces and icy or snow-covered roads, ABS vehicles can stop in a shorter distance than a non-equipped vehicle with locked wheels. If the first car has ABS, it can come to a stop without skidding. If the wheels of the second car lock, however, it can skid into the first car. "The better your own braking capabilities, the more likely that a following vehicle with average braking will hit you," states the 1994 report.
It should be emphasized that in a rear-end collision, the driver who hits a car from behind is usually considered to be at fault.

4. Why does some research suggest passenger cars equipped with ABS may be more likely than cars without ABS to suffer significant increases in side impacts with fixed objects?

Side impacts infer a loss of vehicle control. Impacts with fixed objects, with the exception of cars parked or left on the road, imply the vehicle left the roadway. It may appear that ABS-equipped vehicles are more likely to suffer such increases in these types of crashes but, in fact, they are not. Because this type of crash accounted for only 3 percent of the crashes NHTSA analyzed, any increase would change this statistically small event significantly.

5. Why are light trucks equipped with rear-wheel anti-lock brakes (RWAL) more likely than light trucks without RWAL to become involved in nonfatal and fatal front crashes with another vehicle?

Alliance members have not found any evidence that vehicles with rear-wheel anti-locks are more likely than vehicles with conventional braking systems to become involved in such accidents. They may be, however, more likely than four-wheel anti-lock vehicles. By eliminating rear-wheel lock, they provide increased directional stability and prevent the vehicle from running off the road. A rear-wheel anti-lock system may not prevent front wheels from locking and requires steering input and front-wheel lock control by the driver to avoid a frontal collision. Findings in the NHTSA report of May 1995 indicated a significant reduction in nonfatal roll-over crashes and side impacts with fixed objects with RWAL-equipped vehicles
With four-wheel anti-locks, the braking system modulates the braking pressure, preventing wheel lock on all four wheels and therefore maintaining steerability. Drivers of RWAL vehicles, on the other hand, control the braking and thus the lock prevention capabilities of the front wheels. If the driver steps too firmly on the brake pedal, the front wheels can lock and prevent steering -- the same that would happen with conventional brakes, but the vehicle would remain on the road. With just enough force applied, the driver of an RWAL vehicle can maintain control.
One of the Alliance's goals is to educate drivers about the difference between four-wheel and rear-wheel anti-locks. Simply put, drivers of four-wheel ABS cars should step firmly on the brake in an emergency stopping situation and keep their foot on the pedal. Drivers of RWAL vehicles should not step as firmly, and if they feel the wheels begin to lock, they should withhold some pressure.

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