The Drinking Pedestrian - A 20-year Follow-up

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1 The Drinking Pedestrian - A 20-year Follow-up Andrew Clayton*, M aggie Colgan* and Robert Tunbridge** * The British Institute of Traffic Education Research. Kent House, Kent Street, Birmingham B5 6 QF UK. **Road Safety Division, Department of Transport, 76 Marsham Street, London SW 1P 4DR UK. INTRODUCTION Studies on the role of alcohol in adult pedestrian accidents are rare in comparison to the wealth of research on alcohol and driving. A review of five British studies carried out between 1966 and 1974 found that three showed broad agreement in suggesting that 30-33% of fatally injured adult pedestrians had positive BACs and 17-22% had BACs in excess of 0.10% (Clayton et al 1977). A study of injured pedestrians (Everest et al 1991) found that 27% had BACs above,08g/dl and 17% were above 0.15g/dl. More recently, Holubowycz (1995), in a review of seven Australian studies, reported that 20-30% of adult pedestrian casualties had BACs over 0.15g/dl and that alcohol involvement was higher amongst fatalities. A study of adult fatal pedestrian accidents in France (Fontaine et a! 1995) found that 35% had BACs at or above,08g/dl and 21% were at or above,20g/dl. Clayton et al (1977) reported the results of a case control study of fatally-injured pedestrians. They found that, for male pedestrians, the relative accident risk within the range g/dl was over three times that of a pedestrian with zero BAC. For the 0.16g/dl+ BAC group, the relative risk was at least fourteen times greater. For females, the risk for pedestrians with BAC above 0.12g/dl was over thirty six times that of sober pedestrians. A case-control study involving 290 injured pedestrians in Victoria (Alexander et al 1990) found similar results. The relative risk of accident involvement for males began to increase in the g/dl range and was substantially higher at BACs above. 15g/dl. Risk relationships could not be calculated for females because of the absence of controls with BACs above.15g/dl

2 OBJECTIVES The two principal objectives of the present three-year study are: to replicate the controlled study of fatal adult pedestrian accidents undertaken by Clayton et al (1977), and to extend the study to include injured pedestrians taken to hospitals within the study area. This paper presents some initial results from the study and permits some comparisons to be made with the results from the 1977 study. COM PARISON OF 1977 AND 1997 STUDIES Baseline data The 1977 study examined data on all fatal adult (=>16 years) pedestrian accidents that occurred with the W est Midlands area (population 2.8M) during the seven-year period 1 January 1969 to 31 December The present (1997) study used the same area (with the omission of one sub-district) and examined the data on accidents occurring between 1 January 1990 and 31 December Between the two study periods, the mean annual rate of adult pedestrian fatalities has almost halved from 113 to 59. During the period , the annual rate varied only slightly. By contrast, it has declined steadily since Age and Gender There appear to have been a shift in the age distribution between the two studies. The 1997 study had a higher proportion of pedestrians with the age group and correspondingly fewer within the age group. The high proportion of pedestrians aged 65 and over has remained unchanged. There was no significant difference in the gender distribution between the two studies. About 60% of pedestrian fatalities were male. (Table 1). Blood Alcohol Concentrations It is normal procedure for the blood samples of most road accident victims who die within 12 hours of the accident to be analysed for alcohol content. The proportion of pedestrians for whom the BAC is known has declined from 85% (1977) to 6 6 % (1997). This loss of data coupled with the decline in overall pedestrian fatalities resulted in BAC data being available for only 95 pedestrians (67 male; 28 female) in the 1997 study as compared to 344 pedestrians (194 male; 150 female) in the 1977 study

3 In 1977, 47% of male pedestrians had positive (>,009g/dl) BACs and 10% (21% of positive BACs) were at or above,25g/dl. In 1997, 43% had positive BACs and 19% (40% of positive BACs) were at,25g/dl or above. By contrast, 9% of female pedestrians in 1977 had a BAC at or above 0.08g/dl; in 1997, the incidence was zero. (Table 2) Table 1: Comparison of 1977 and 1997 Studies Variable 1977 Study 1997 Study Sig Level (N=786) (N=289) (Chi-square) % % Gender Male NS Age p= Table 2: BAC distributions by gender (1977 and 1997) BAC (g/dl) Males Females 1977 study 1997 Study Sig Level 1977 Study 1997 Study Sig Level (N=194) (N= 67) (Chi- (N= 150) (N = 28) (Fisher % % square) % % Exact Test) p< NS => Although the numbers are small, Table 3 suggests that the increase in the percentage of male pedestrians with high BACs is caused by a higher proportion of younger pedestrians with higher BACs. Aggregating the age groups into and 65+, the 1997 study had a higher

4 proportion of year-olds with BACs above 0.16g/dl (Using Fisher s Exact Probability Test p<0.05). Table 3: M ale pedestrians with BACs =>.16g/dl: 1977 and 1997 Age group 1977 Study (N=194) 1997 Study (N=67) No % within age group No % within age group THE 1997 STUDY In view of the lower testing rate in the 1997 study, the incidence of testing was determined for all major variables to determine any inherent biases in the data. The results are shown in Table 4. Age, Gender and M arital Status Most pedestrians were 65 years or older. The testing rates by age group were not significantly different. O f those pedestrians between 16 and 39, 12 (67%) had BACs above,08g/dl, compared to only 6 % of those aged 65 or over. Males comprised the majority (56%) of the sample. They were significantly more likely to be tested (83% vs 44%; p<0.001). All fatalities with BACs at or above,08g/dl were male. Because of the small numbers, the sample was divided into Single/Divorced/Separated and Married/Widowed. Married or widowed pedestrians comprised nearly two-thirds of the sample. Only 16% of this group had BACs above.08g/dl compared to 44% of single/divorced/separated pedestrians (p<.01) Accident Circumstances Most (61%) of accidents occurred during the day ( ). The testing rate for pedestrians involved in night-time fatalities was significantly higher than for day-time accidents ( 8 8 % vs 52%; p<.001). All pedestrians with BACs above.08g/dl were involved in night-time accidents. The day of week of the accident was divided into two groups: Monday

5 Thursday and Friday-Sunday. No significant differences were observed. Most pedestrians (79%) were attempting to cross the road at the time of the accident. Almost two thirds (62%) of pedestrians who were not crossing the road at the time of the accident had BACs above.08g/dl as compared with 16% of those who were crossing (p<0.001). Examples of noncrossing behaviour include walking in the road and standing (or lying) in the road not moving. Variables which showed no relationship with either the incidence of alcohol testing or the BAC of the pedestrian included the posted speed limit, the existence of controlled crossing facilities within 50m of the accident, and whether or not the accident occurred within 20m of a junction. Table 4: Characteristics of 1997 Sample Variable All fatalities dying All tested fatalities All tested fatalities within 1 2 hours (N=144) (N=95) with BAC >0.08g/dl (N=26) All % No % tested No % of tested Male Female years years >=65 years Single/div/sep M arried/widowed Day ( ) Night ( ) M onday-thursday Friday-Sunday Crossing road Not crossing road

6 DISCUSSION AND CONCLUSIONS The comparison of the results of the 1977 and 1997 studies is complicated by the reduction in the proportion of adult pedestrians dying within 1 2 hours of the accident who are tested for alcohol. The evidence suggests a bias against testing an individual when the perceived probability of alcohol being present is low. If true, then the reported BAC distribution will tend to over-estimate the true incidence of alcohol amongst all adult fatally-injured pedestrians. The effect of any bias will be least amongst those pedestrians with high BACs and therefore the difference in BAC distributions of male pedestrians may well be real. If so, then the reason appears to be an increase in the number of younger pedestrians and an increase in the proportion of these pedestrians with high (=>0.16g/dl) BACs. If safety engineering measures are to be successful in reducing the severity of all pedestrian accidents, then more attention will need to be paid to the alcohol levels of pedestrians. REFERENCES Alexander, K, Cave, T and Kyttle, J (1990). The role of alcohol and age in predisposing pedestrian accidents. Melbourne: Road Traffic Authority, Pedestrian Accident Study, Report No 6. Clayton, A B, Booth, A C and McCarthy, P E (1977). A controlled study of the role of alcohol in fatal adult pedestrian accidents. Crowthorne: Transport and Road Research Laboratory, Report SR332. Everest, J T, Banks, S, Hewer, P A and Mineiro, J (1991). Drinking behaviour and breath alcohol concentrations of road accident casualties. Crowthorne: Transport and Road Research Laboratory Report R R 311. Fontaine, H, Gourlet, Y and Ziani, A (1995). Les accidents de pietons. INRETS Report 201. Holubowcyz, O T (1995). Alcohol-involved pedestrians; the Australian experience. In Kloeden, C N and McLean, A J (Eds) Proceedings of IS 111 International Conference on Alcohol, Drugs and Traffic Safety, August, Adelaide, ACKNOW LEDGEM ENTS The co-operation and assistance of HM Coroners and their staff in the West Midlands is gratefully acknowledged. This paper has been produced as part of a contract placed by the Department of Transport. Any views expressed in it are not necessarily those of the Department