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Report Critical of Safety Benefits of Antilock Brakes

Copyright AA1Car

The safety benefits of antilock brakes (ABS) have come under fire by such groups as the Highway Loss Data Institute (HLDI), who published a report that said antilock brakes are NOT reducing either the frequency or the cost of crashes.

According to the HLDI report, 1,000 fatal crashes during a 10 year period were studied to see if ABS made a difference one way or the other. The HLDI researchers found that a person in an ABS-equipped vehicle actually had a 45% greater chance of dying in a single-vehicle crash than someone in a vehicle without ABS. The chance of dying went up also went up 65% when the vehicle was involved in a single-car accident on wet pavement.

On the other hand, the report also found that multi-vehicle fatal crashes on wet roads were actually 24% lower for ABS-equipped cars, and that ABS-equipped cars killed 27% fewer pedestrians and bicyclists. But these reductions were offset by a 28% higher fatality rate involving accidents where an ABS-equipped vehicle ran off the road and rolled over.

The HLDI news release also cited a separate study that General Motors did of crashes involving ABS-equipped vehicles in two states. The GM study found that ABS-equipped vehicles had 3% fewer accidents overall but suffered a 44% increase in rollovers.

Some insurance companies have cited the HLDI study as "evidence" that ABS does not necessarily reduce accident claims (insurance losses) so they can eliminate previously offered discounts for having ABS on a vehicle.

The National Highway Traffic Safety Administration (NHTSA) said the HLDI report findings may be explained by several factors: that drivers who are unfamiliar with ABS may not keep their foot on the brake or may pump the pedal during a panic stop, reducing the effectiveness of the ABS system. ABS may also give some drivers a false sense of security, possibly encouraging them to drive more aggressively and run off the road.

Shortly after the HLDI report was released, two auto industry associations released a study of their own that said people who drive ABS-equipped vehicles actually suffer fewer injuries, and that the overall accident rate for ABS-equipped vehicles is about 10% less than that for vehicles without ABS. The overall fatality rate, however, was found to be no different.

Responding to the negative reports, four ABS manufacturers (Bosch, Delphi, Continental Teves and Kelsey-Hayes) formed a group called the ABS Education Alliance and did their own analysis of the numbers. The Alliance found that vehicles equipped with four-wheel ABS systems were involved in 2,800 fewer frontal impacts (a category that accounts for 82% of the crashes analyzed by the NHTSA).

The ABS Education Alliance also launched the "America brakes for safety" campaign to help motorists learn how to use antilock brakes properly (things like not pumping the pedal when braking hard, remembering to steer while braking to avoid an accident, having their ABS system checked if the ABS warning lamp is on).

GROWTH OF ABS HAS LEVELED OFF

For awhile, it seemed as if all cars and trucks would eventually have ABS as standard equipment. But in spite of the rapid growth of ABS availability in the early 1990s, the number of vehicles equipped with ABS has been flat.

Since 1994, the percentage of domestically produced vehicles actually equipped with ABS has been about 58%.

Though ABS systems keep coming down in price and are getting better every year, the vehicle manufacturers say it is still an expensive option that many consumers are not willing to pay for. Consumers would rather have options such as air conditioning and a high end sound system than ABS. Consequently, the auto makers have been shipping models loaded with options other than ABS to their dealers, thus limiting the public's ability to buy an ABS-equipped vehicle even if they wanted the safety feature.

ABS LEGAL BATTLES & RECALLS

General Motors and Chrysler have both had their share of ABS legal hassles. The RWAL rear-wheel ABS system manufactured by Kelsey-Hayes and used on various 1989 to 1996 Chevrolet and GMC trucks has been under investigation by the NHTSA for a variety of complaints including loss of pedal, excessive pedal travel, failure to stop the vehicle under certain conditions, and excessive front pad wear. Since 1994, NHTSA has reportedly received over 10,000 complaints on ABS problems with GMC and Chevy trucks. A class action suit filed against GM and Kelsey-Hayes on behalf of owners of these vehicles was dismissed August 1, 1997. NHTSA has taken no action of its own, but GM did do a voluntary recall of 1.1 million Chevy and GMC trucks with the Kelsey-Hayes EBC4 ABS system. The recalled models include 1991-1996 four-wheel drive Blazer, Jimmy, S-10 and GMC Sonoma, 1992-1995 Chevy Astro vans and GMC Safari vans, and 1993-1996 G-Series vans.

The Bendix 10 ABS system used on 1991-93 Chrysler minivans (Dodge Caravan, Plymouth Voyager & Chrysler Town & Country), Chrysler New Yorker, Imperial and Dynasty, and 1991-92 Eagle Premier and Dodge Monaco, came under fire for reportedly experiencing a high ABS pump failure rate. The NHTSA reportedly received nearly 2,000 complaints about problems with this particular ABS system, including numerous accidents and injuries (but no deaths). The NHTSA investigation found that most complaints centered on the pedal sinking to the floor causing a loss of brakes. The condition is often intermittent and occurs without warning.

The NHTSA investigation of the Chrysler Bendix 10 ABS problem resulted in a safety recall (#685) being issued in August 1996. The recall listed the ABS actuator piston and pump/motor assembly as the culprit. The recall notice issued to Chrysler dealers specified a test procedure for checking out the Bendix 10 ABS system:

1. Check for trouble codes.

2. If none are found, depressurize the accumulator by pumping the brake pedal 40 times with the ignition off, then install a special leakage test fixture (#6997) to test system pressure and to check for leaks. Pump pressure should build to 1800 to 2200 psi, then shut off. Pressure should hold and drop less than 200 psi in two minutes.

If the system builds adequate pressure, but the hydraulic control unit side of the system drops more than 200 psi in two minutes, the master cylinder actuator piston assembly needs to be replaced.

If the system builds adequate pressure but the pump/motor side of the system drops more than 200 psi in two minutes, the pump/motor assembly needs to be replaced.

In addition to sending out a recall notice to all the owners of the affected vehicles, Chrysler also extended the warranty on the ABS system components to 10 years or 100,000 miles. The extended warranty applies to the ABS components only and not the entire brake system.



Antilock Brake Safety Precautions on Late Model Cars

A growing number of late model cars are equipped with antilock brake systems that can precharge the brakes in anticipation of braking (to reduce braking reaction time), or actually apply the brakes automatically as a function of the collision prevention system (automatic braking).

CAUTION: If you are doing any type of brake work on these vehicles, the braking system must be deactivated before you work on the brakes, otherwise the system may energize the brakes unexpectedly causing the caliper pistons to push outward with considerable force. This could pinch your fingers if they are between the pads and rotors. If the pads have been removed, the pistons can blow out of their calipers. This can happen even when the ignition and engine are off!

The antilock brake system can be deactivated by locating and removing the main power fuse for the ABS system, or by using a scan tool to temporarily deactivate the system. Disconnecting the battery also works, but this may cause loss of certain memory settings in various vehicle modules. See Battery Disconnect Cautions & Problems for more information on this subject.


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Antilock Brake Related Articles:

Antilock Brakes (ABS)

ABS System Application Chart (by vehicle year, make & model)

New ABS Diagnostic Testers

Pulling ABS Diagnostic Codes

Honda Antilock Brakes

Chrysler Dodge Plymouth Minivan Bendix 10 Antilock Brakes

GM Delphi DBC-7 ABS Antilock Brakes

Jeep Bendix 9 Antilock Brakes

Kelsey-Hayes RWAL Rear Wheel Antilock Brakes

Kelsey-Hayes 4WAL Antilock Brakes

Teves Mark 20 Antilock Brakes

Electronic Stability Control

Brake-By-Wire

GM SUV ABS Recall

Toyota Prius Brake Recall

To More Technical Info Click Here to See More Automotive Technical Articles

Antilock Brake Related Links:

Foundation for Highway Safety ABS Precautions

Foundation for Highway Safety ABS FAQs

Insurance Institute for Highway Safety ABS FAQs

NHTSA Antilock Brake Information

NHTSA Safety Recall Database


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