英文原文The antilock braking system anomaly: a drinking driver problemDavid W. Harless , George E. HofferDepartment of Economics, Virginia Commonwealth Uni_ersity, Box 844000, Richmond, VA 23284, USAReceived 30 November 2000; received in revised form 19 February 2001; accepted 28 February 2001An important anomaly with the incorporation of safety appliances into motor vehicles is the ineffectiveness and even perverse effects of antilock braking systems (ABS), particularly as measured by fatal crash involvement. Analyses of insurance claims in the US (Highway Loss Data Institute, 1994, 1995) showed no change in claim frequency after a set of GM vehicles adopted antilock brakes in 1992 despite engineering studies showing antilock brakes resulted in much better braking performance, especially on wet roads. Using the same group of GM vehicles, Farmer et al. (1997) found that adoption of ABS resulted in more 19931995 crashes resulting in the death of an ABS vehicle occupant. Another group of vehicles that adopted antilock brakes as early as 1985 were found to have been involved in both more fatal crashes resulting in the death of an ABS vehicle occupant and more involvements overall. These perverse effects were most evident in single-vehicle crashes. Updating the earlier paper with 19961998 data on the same two groups of vehicles, Farmer (2001) finds that the ABS-equipped vehicles no longer had a worse fatal accident involvement rate16.The ABS anomaly has sparked a large program of research at the National Highway Transportation Safety Administration, the many components of which are described by Garrott and Mazzae (1999). Several explanations have been forwarded for the anomaly. First, consistent with the risk compensation hypothesis, the higher incidence of fatal crashes could be due to increased speed and aggressiveness by drivers of ABS equipped vehicles (Evans, 1995; Evans and Gerrish, 1996). Second, there may be problems with improper operation of ABS-equipped vehicles: the higher incidence of single vehicle crashes could be due to abrupt steering changes by panicked drivers inexperienced with ABS reacting instinctively in emergency situations (Kahane, 1994). With ordinary brakes, such steering changes have no effect if the brakes are locked. The subsequent attenuation of the ABS anomaly (Hertz et * Corresponding author. Tel.: +1-804-8287190; fax: +1-804-8281719.E-mail address: dwharlesvcu.edu (D.W. Harless).0001-4575/02/$ - see front matter 2002 Elsevier Science Ltd. All rights reserved.PII: S0001-4575(01)00030-6 D.W. 334 Harless, G.E. Hoffer / Accident Analysis and Pre_ention 34 (2002) 333341 al., 1998, 2000; Farmer, 2001) may be due in part to drivers accumulating more experience using antilock brakes.1In this paper we report strong evidence supporting Kahanes hypothesis that the ABS anomaly occurs because of improper operation of antilock brakes. We examine the sample of vehicle lines adopting ABS used by Farmer et al. (1997) and Farmer (2001) and apply the same risk ratio analysis to show that the perverse effects of ABS are confined largely to drinking drivers.We find dramatic differences between drinking and sober drivers in the rate of fatal accidents in ABS equipped vehicles compared to control vehicles. For example, in the sample of GM vehicles that adopted ABS in 1992, consider the rate of fatal accident involvements resulting in the death of an ABS vehicle occupant in the years 19931995: In the risk ratio analysis we find that the number of such accidents involving drinking drivers was 82% higher than expected (P=1.6E11). When there is an ABS problem (e.g., the years 19931995 for the GM vehicle sample) there are large differences between the risk ratios for drinking and sober drivers; when there is no ABS problem (e.g., the years 19961998) the differences between drinking and sober drivers disappear. We also show that the attenuation of the ABS problem after the first four years of vehicle service, as in Farmer (2001), was also evident in the earlier group of vehicles which adopted ABS as early as 1985.We follow Farmer et al. in comparing the fatal accident involvement rates of ABS-equipped 1992 GM vehicle lines (the first year that antilock brakes were adopted as standard equipment in these vehicle lines) to otherwise similar 1991 model-year vehicle lines. To parallel Farmer et al. (1997) and Farmer (2001), Table 1 provides risk ratios for both 19931995 fatal accidents (left side) and 19961998 fatal accidents (right side).2To demonstrate our (very close) replication of the previous findings, the first line of the table shows our results for all fatal accident involvements resulting in the death of an ABS vehicle occupant. For example, from the FARS files (National Highway Traffic Safety Administration, 1997) we observed 328 accidents involving the selected ABS-equipped, 1992 model-year GM vehicle lines during the years 1993l995.3 Under a null hypothesis of no