Driver Crash Avoidance Behavior with ABS in an Intersection Incursion Scenario on Dry Versus Wet Pavement

ABSTRACTThe National Highway Traffic Safety Administration(NHTSA) has developed its Light Vehicle Antilock BrakeSystems (ABS) Research Program in an effort todetermine the cause(s) of the apparent increase in fatalsingle-vehicle run-off-road crashes as vehicles undergo atransition from conventional brakes to ABS. As part of thisprogram, NHTSA conducted research examining drivercrash avoidance behavior and the effects of ABS ondrivers’ ability to avoid a collision in a crash-imminentsituation. The study described here was conducted on atest track under dry and wet pavement conditions toexamine the effects of ABS versus conventional brakes,ABS brake pedal feedback level, and ABS instruction ondriver behavior and crash avoidance performance. Thisstudy found that drivers do tend to brake and steer inrealistic crash avoidance situations and that excessivesteering can occur . However, a significant number of roaddepartures did not result from this behavior for eitherpavement condition. ABS was found to reduce crashessignificantly on wet pavement as compared to conventionalbrakes.INTRODUCTIONSince 1985, antilock brake systems (ABS) have beenincreasingly available on many passenger car and lighttruck make/models. ABS have been sold as an addedsafety feature which enhances drivers’ ability to control avehicle and, in some cases, improves vehicle stoppingperformance. In the interest of reaping the benefits ofABS in terms of a reduction in crashes, the HighwaySafety Act of 1991, Section 2507 charged the NationalHighway Traffic Safety Administration (NHTSA) with thetask of determining whether ABS should be required on allpassenger vehicles.As a result, NHTSA undertook a series of investigations todetermine the potential benefits of ABS and the effect ofABS on crash rates. Test programs have shown that ABSappear to be very promising safety devices whenevaluated on a test track. Under many pavementconditions antilock brake systems allow the driver to stopa vehicle more rapidly while maintaining steering controleven during situations of extreme, panic braking. Brakeexperts anticipated that the introduction of ABS onpassenger vehicles would reduce both the number andseverity of crashes. However, a number of crash dataanalyses have been performed in recent years by NHTSA,automotive manufacturers, and others which indicate thatthe introduction of ABS has not been found to beassociated with a reduction in crashes to the expectedextent. CRASH DATAKahane [1] found that, with the introduction of ABS,involvements in mutli-vehicle crashes involving fatalities onwet roads were significantly reduced by 24 percent, andnonfatal crashes by 14 percent. However, thesereductions were offset by a statistically significant increasein the frequency of single-vehicle, run-off-road crashes, ascompared to cars without ABS. Run-off-road crashes, asconsidered in this report, included rollovers, side impactswith fixed objects , and frontal impacts with fixed objects.Fatal run-off-road crashes were up by 28 percent andnonfatal crashes by 19 percent. On wet roads, fatal run-off-road crashes increased 17 percent and non-fatal run-off-road crashes increased by 24 percent. On dry roads,fatal run-off-road crashed increased by 29 percent whilenon-fatal crashes increased by 17 percent.Hertz, Hilton, and Johnson [2] presented results forpassenger car run-off-road crashes according to thefollowing crash types: rollovers, side impacts with parkedvehicles or fixed objects, and frontal impacts with parkedvehicles or fixed objects. For dry roads, ABS was found tobe associated with a 17 percent decrease in rollovercrashes, a 13 percent decrease in frontal impacts withparked vehicles or fixed objects, and a 7 percent increasein side impacts with parked cars or fixed objects. Forpedestrian crashes, ABS was associated wtih a 30 percentreduction on dry roads and a 10 percent reduction inunfavorable road conditions (i.e., wet, snowy, icy, gravel). In regards to only those crashes involving fatalities, ABSwas found to be associated with a 51 percent increase infatal rollover crashes on dry roads. For fatal side impact