Road Trauma in Perspective

Paper presented to Vehicle Accidents their Cause - Reconstruction - Law Conference
Melbourne, 28th & 29th July, 1995, Monash University Department of Civil Engineering

Abstract

Road fatalities in Victoria fell from 776 in 1989 to 378 in 1994. The latter figure corresponds to 1.3 deaths per 10,000 registered vehicles being one of the lowest recorded rates among motorised countries. During the same period there was a similar drop in serious injuries. Despite these large reductions in deaths and injuries on our roads, road trauma is still a major problem.

A review of countermeasures which have been shown to be associated with the recent reductions in deaths and serious injuries was undertaken. They included:

The effect of the downturn in the economy and reduced alcohol sales over the same period was also considered.

The contributions of each of the major countermeasures and other factors to the reductions in serious casualty crashes during each of the years 1990 to 1992 were estimated.

1. Introduction

Despite considerable progress in recent years, road trauma is still the single largest cause of death for persons aged between 1 and 44 years of age.

In Victoria each year nearly 400 persons are killed on our roads and some 6,000 are admitted to hospital as a result of a road crash.

Progress in road safety is usually measured in terms fatality rate. Figure 1 shows annual fatalities per 10,000 registered vehicles for Australia, Victoria and those countries which have the best road safety records.

It can be seen that the sustained reductions from 1970 to about 1983 brought Victoria and Australia close to the levels of those countries with the best rates. Then, after a period of relatively little progress, a large drop occurred in Victoria during the three years 1990-92 and has been maintained. The 1994 rate of 1.3 deaths/10,000 registered vehicles is below the latest rates available for other countries. (Care should, however, be taken in comparing the Victorian rate with those of other countries, because there are undoubtedly states/regions in those countries with fatality rates considerably below their national average, just as in Australia the ACT rate is below that for Victoria.)

In the health sector, fatality rate is usually measured in terms of annual deaths per 100,000 population and this is shown in Figure 2. While the trends are similar to those in Figure 1, it can be seen that countries with a smaller number of vehicles per head of population, such as the U.K. and Sweden have a lower rate than the more highly motorised countries such as Canada, United States and Australia.

2. Road Trauma in Victoria

The remainder of this paper will concentrate on the reduction in road trauma which has occurred in Victoria since 1989. As shown in Figure 3 the reductions have not been confined to fatalities, there have been similar reductions in injuries.

Figure 3 - Percentage change from 1984
Fatalities, serious injuries and other injuries, Victoria

It is also interesting to examine the trends in fatalities by type of road user. As shown in Figure 4, there have been reductions in the number of fatalities in each category, but those for drivers, passengers and pedestrians have been much more marked than for motorcyclists. The percentage drop for bicyclists has also been high (over 50%), but it was applied to relatively smaller total.

The main measures which it is considered contributed to the large reductions in road trauma during 1990-92 are:

The periods of implementation for many of these measures coincided and most were applied throughout the State, making evaluation more difficult. Nevertheless, evaluations covering the relevant period have been done on all but the last measure and key aspects of these will be presented in this paper, which is based on an earlier paper presented in 1994 (Cameron, et. al., 1994).

3. Speed Camera Program

New slant radar speed cameras were progressively introduced commencing with four in December 1989 and building to 54 by January 1991. The monthly numbers of speeding tickets (Traffic Infringement Notices) issued following detection by speed cameras are shown in Figure 5. The program included an intensive State-wide mass media publicity campaign "Don't fool yourself - speed kills" which aimed to increase the perception of the level of camera operations, as well as to promote the need for speed enforcement. This multi-media campaign by the Transport Accident Commission (TAC) involved much larger expenditure than previous road safety campaigns. It was launched in April 1990 and maintained at high levels for most of 1990, four months in 1991 and seven months in 1992.

Figure 5 - Monthly number of Traffic Infringement Notices issued for speeding offences detected by speed cameras - Victoria 1989-1992

An evaluation has been undertaken of the effect of the program on crashes during "low alcohol hours", on the basis that the coincident random breath testing (RBT) program could have had only a very small effect on these crashes (Cameron et al. 1992a). During low alcohol hours (Monday - Thursday 6 a.m. to 6 p.m., Friday 6 a.m. to 4 p.m., Saturday 8 a.m. to 2 p.m., Sunday 10 a.m. to 4 p.m.) an average of less than 4% of drivers in serious casualty crashes exceed 0.05% blood alcohol content. Furthermore the majority of RBT operations occurred during high alcohol hours and over 82% of speed camera operations were in low alcohol hours.

Speed cameras had been used mainly on arterial roads in 60 km/h speed zones in both metropolitan and country areas (80-90% of sessions). Their use was also greater in the metropolitan area (70% of sessions) than in the country.

Multivariate time series models were developed to predict expected casualty crash frequency and injury severity for Melbourne and Sydney as a comparison area. The respective unemployment rates in each city were included as co-variates in each model to take account of differential impacts of the downturn in the economy on vehicle use. Similar models were also developed for the "rest of Victoria" and the "rest of NSW" as a comparison area.

The percentage changes from the model prediction in each area of Victoria were then contrasted with those for the corresponding area in NSW. The difference provided the estimated percentage change which was considered to be attributable to the Victorian speed camera program (after allowing for differences in unemployment rates between the two States and any "other factors" which are assumed to have affected low alcohol hour crashes in both States equally).

Figure 6 shows the net percentage reductions in casualty crash frequency and injury severity (defined as the ratio of fatal plus serious injury crashes to crashes involving only minor injury) in low alcohol hours on Melbourne arterial roads when compared with Sydney arterial roads for each of the four periods.

Figure 6 also shows the net percentage reductions on 60 km/h roads in the rest of Victoria when compared with 60 km/h roads in the rest of NSW.

Figure 6 - Estimated Percentage Reductions in Casualty Crash Frequency
and Injury Severity in Low Alcohol Hours

It can be seen that there were statistically significant reductions in casualty crash frequency (in low alcohol hours) in both areas in three of the four periods, but the reductions in severity were confined to Melbourne. The fact that in period T 2(b) the frequency of casualty crashes in Melbourne was not significantly different from Sydney might be explained by the fact that the NSW speed camera program had started in Sydney at the beginning of this period, and there was a significant reduction in such crashes in Sydney during T 2(b).

Other results are given in the full report (Cameron et al. 1992a). When results for the whole of Victoria were considered there was a statistically significant reduction in the frequency of low alcohol hour casualty crashes of 20% during period T 1(b) and 21% during T 2(a). Similarly there were reductions in severity of 28% in T 2(a) and 40% in T 2(b). There were, however, no significant reductions for 100 km/h zones.

Another phase of the study examined the localised effects in time and space related to the camera operations in Melbourne and the receipt of speeding tickets which resulted from each camera session (Rogerson et al. 1994). This phase has found a significant reduction in casualty crashes within one kilometre of a camera site as a result of the receipt of a Traffic Infringement Notice, for two weeks after receiving the penalty (the effect may have been longer). However, there was no statistically significant reduction in casualty crashes which occurred during the week starting on the actual day of camera operations.

4. Random Breath Testing Program

Commencing in September 1989 the use of buses for random breath testing (RBT) was gradually increased, initially in the metropolitan area using four existing buses and progressively throughout the State as 13 new purpose-built highly visible "booze buses" became available during 1990. Increased resources for operating the buses were provided through the use of Probationary Constables in Training. This resulted in the number of RBT tests increasing from around half a million in 1989 to over 900,000 in 1990, and over 1,100,000 in 1991 and 1992. The number of tests per month are shown in Figure 7 for Melbourne and rural Victoria. Buses had become the primary form of RBT in the metropolitan area by November 1989, while in the rural areas the shift to greater use of buses occurred after October 1990.

In December 1989 a major State-wide multi-million dollar publicity campaign "If you drink then drive - you're a bloody idiot" was launched to support the new RBT operations. Further media launches and publicity for the new booze buses occurred in April and September 1990.

Two different analyses of the effect of the RBT initiative have been conducted (Drummond et al. 1992; Cameron et al. 1992b; Cavallo and Cameron 1992). The first was a quasi-experimental time series design which used the more remote rural areas of Victoria (R2), which had received less RBT, as a comparison area for Melbourne and for the remaining rural areas, which were closer to Melbourne (R1). Sydney was also used as a comparison area for Melbourne.

The second was a multivariate time series approach, with Sydney as a comparison area for Melbourne and the "rest of NSW" as a comparison area for the "rest of Victoria". Unemployment rate was used as a co-variate (as in the speed camera program evaluation) to account for the effect of the economic downturn on vehicle use.

Both studies limited their evaluation to fatal crashes and serious casualty crashes in "high alcohol hours". This is reasonable because an average of about 38% of serious casualty crashes in these hours involve a driver with a BAC over 0.05%, while the corresponding percentage during the remainder of the week (low alcohol hours) is below 4%. In addition it was assumed that the speed camera program had little effect during these high alcohol hours, because only 10% of camera operations occurred during these hours.

Figure 8 shows the results from these two studies. It should be noted however, that while the results shown for Melbourne use Sydney as the comparison area, the rural results for the quasi-experimental study are for Rural area R1 (the area with greater RBT bus operations) compared with Rural area R2, whereas the second study compares the whole of rural Victoria with rural NSW.

It can be seen that even through the treatment and comparison areas for "rural" are different in the two studies, three of the four estimated net reductions are similar, namely:

The different results for Melbourne serious casualty crashes appear to result from the different analysis methods used (Cavallo and Cameron 1992). The multivariate time series analysis (Study 2) was capable of being extended to 1991 using regression modelling and found a 24% significant reduction in rural serious casualty crashes (high alcohol times).

As shown in Figure 8, the RBT program was also accompanied by progressive reductions in the proportion of drivers and motorcyclists killed (and tested) with a Blood Alcohol Content (BAC) exceeding .05%.

Table 1 - Driver/Motorcyclist Fatalities by BAC
(those with known BAC readings only)

	Number below .05% BAC	Number exceeding .05% BAC	Percent exceeding .05% BAC
1988	174	105	37.6
1989	236	113	32.4
1990	173	73	29.7
1991	173	70	28.8
1992	149	39	21.0

5. Bicycle Helmet Law

A law which required all bicyclists to wear an approved bicycle safety helmet came into effect in Victoria on 1 July 1990. This resulted in an increase in the estimated overall helmet wearing rate from 31% to 75%. Based on TAC claims, in the first 12 months after the introduction of the law there was a reduction of 51% in the number of bicyclists with a head injury killed or admitted to hospital and the corresponding number without a head injury dropped 24%. As shown in Figure 9, in the second year the corresponding reductions were 70% and 28% respectively.

While the large reduction in head injuries was a clear indication of the effect of the law, the reduction among bicyclists without a head injury was shown to be at least partly a result of reduced cycling, particularly among teenagers (Finch et al. 1992). A portion of both drops may of course be attributable to the economic downturn, or the speed camera and RBT programs.

As bicyclist casualties represent only about 3% of total road trauma, these large reductions could only represent a small percentage of the total reduction during the period 1990-1992.

Freeway Speed Limit

The 110 km/h speed limit on high standard rural and outer metropolitan freeways was lowered to 100 km/h at the end of September 1989. An analysis showed a 19.3% drop in casualty accident rate, when adjusted for changes for a control group of roads over the 814 days until the end of 1991 (Sliogeris 1992). This corresponds to a drop of 84 casualty accidents per annum of which some 39 per annum were fatal or serious injury accidents, which is less than 1% of the reduction during the period 1990-92.

6. Improvements to the Road System

In regard to progressive improvements to the road system, particularly at locations or along routes with a bad accident record, earlier studies have shown that reductions in casualty accidents of 10-50% have been achieved, yielding very high benefit cost ratios (Corben et al. 1990; Tziotis and Bui 1992; Ogden 1992). However in any one year during the period of study, available resources have limited works to sites with total casualty accidents of less than 1,500 per annum. Assuming a 30% average reduction, the additional annual reduction from one year's program would be up to 450 casualty accidents, ie. about 4% of the total drop in casualty accidents. Naturally the cumulative effect after the second year of the program would be double that for the first year.

Such road improvements are important over the longer term, because they continue to provide these reductions each year for the life of each treatment. In fact, VIC ROADS has estimated total savings of 9,105 casualty accidents (cumulative) resulting from the treatment of 1,998 sites under the accident black spot program during the period 1982 to 1992 (Anderson 1993). However, their contribution to the large downturn during the three years, 1990-1992, could only be relatively small.

7. Economic Activity

Various overseas and Australian studies have shown that it is possible to construct models which link downturns in economic activity with reductions in road fatalities, taking into account changes in road safety measures and other factors where relevant (Hakim et al. 1991; Haque 1991; Pettit 1992). After an extensive examination of relevant variables, a study developed a model which explained about 50% of the variations in monthly Victorian road fatalities during the period 1985 to 1990. (Thoresen et al. 1992)

The model estimated that in 1990 a reduction of 53 fatalities could be associated with the increase in unemployment. This represents a reduction of 6.8% of the 1989 road toll or about one quarter of the total drop in 1990. For 1991 the model indicated that perhaps one third of the reduction from 1989 could be associated with unemployment.

8. Special Enforcement Programs

The Victoria Police have implemented various State-wide enforcement programs of high intensity but limited duration, often directed at certain classes of road use and supported by publicity. There have also been special campaigns undertaken in certain areas in accordance with the road safety calendar directed at increased seat belt wearing and driver fatigue. It is likely that they each made a contribution to the overall reductions but to date no specific evaluations of their effects on casualties have been published.

9. Overall Effects on Road Casualties in Victoria since 1989

The separate studies described above have reported various reductions in fatal or casualty crashes associated with specific programs implemented during the period 1990 to 1992. While all of these studies have covered 1990, not all have extended into 1991 or 1992. Furthermore, the reductions have been expressed in different ways. A need was identified to combine the results to determine the relative contributions of the various measures and other factors to the overall reduction in road casualties in Victoria since 1989 (Vulcan 1993).

Cameron et. al. (1994) describe the development of multiplicative models fitted to the monthly numbers of low alcohol hour serious casualty crashes in Melbourne and rest of Victoria separately, during 1983-92. The explanatory variables used included:

Similarly separate multiplicative models were fitted to the monthly numbers of high alcohol hour serious casualty crashes in Melbourne and the rest of Victoria during 1983-1992. The explanatory variables included:

Estimates of the contributions of the RBT and speed camera programs (and their supporting publicity) were given priority because of their potential to have broad effects, since these programs are not focused on crashes involving only particular road users or occurring only on particular parts of the road system.

A method was developed to decompose the models to estimate the separate effects of the countermeasures and other factors, and then to combine the results from the four models (covering low and high alcohol times of the week and two regions of Victoria) to estimate the overall contribution of each measure/factor to the reduction in serious casualty crashes in Victoria during each of the years 1990 to 1992 (Cameron and Newstead 1993). The method estimates each contribution as the percentage reduction in serious casualty crashes apparently due to the measure/factor. It should be noted that these percentages cannot simply be added up to estimate the total contribution. If more than one contributor is being considered, the percentage reduction of each must be applied in turn. The results are shown in Figure 10, with those for 1993 added.

Figure 10 - Estimated contribution to the reduction in serious casualty crashes
Note: These diagrams do not show the effect of road improvements,
which were included in the expected trend.

10. Discussion

It is possible that the speed camera program may have had an effect on high alcohol hour serious casualty crashes (as well as low alcohol hour crashes). However, as most of the camera operations were during low alcohol hours and in order to try to separate the effects of the RBT and speed camera programs, the speed camera operations (ie. camera hours and TINs issued) were excluded from the high alcohol hour crash models. Similarly, the number of RBTs, drink-driving publicity levels, and the index of alcohol sales were excluded from the low alcohol hour crash models because drivers have BACs over 0.05% in less than 4% of these crashes.

Based on the models fitted to monthly variations in serious casualty crashes in Victoria to the end of 1992, it appears that the major road safety programs combining Police enforcement and mass media publicity have contributed to most of the reduction in these crashes during 1990-92 when compared with levels expected. These road safety programs are estimated to have contributed reductions in serious casualty crashes of 26-29% during these three years.

In addition to these major programs, it appears that reduced economic activity and reduced alcohol sales have also contributed to the reduction in serious casualty crashes. The contribution of increased unemployment rates is estimated to be 1% reduction during 1990 (principally in the second half of the year), 11% during 1991 and 14% during 1992. The relatively small contribution of unemployment rates during 1990 should be compared with an earlier estimate that increased unemployment contributed to a decrease of about 7% in Victorian road fatalities during that year (Thoresen et al. 1992). If increased unemployment during 1990 led to a reduction in certain types of vehicle use (eg. discretionary travel at night), it may be that this vehicle use was associated with a higher risk of fatal outcome than serious injury.

Together the road safety programs, reduced economic activity and reduced alcohol sales appeared to have produced reductions in serious casualty crashes of 32% during 1990, 43% during 1991 and 47% during 1992, compared with expected levels.

11. Conclusions

Victoria has experienced unprecedented reductions in road fatalities and injuries during the three years 1990 to 1992 and these have been maintained up to 1994. The bulk of the reduction can reasonably be attributed to the two major road safety programs, the random breath testing program and the speed camera program, each supported by publicity.

The other measures, namely continuous improvement of the road system, the bicycle helmet law and the freeway speed limit reduction each had significant, but smaller effects. It appears that the reduced economic activity has also contributed to the observed reductions. It is unclear whether the reduction in alcohol sales may have been, at least in part, due to the increased random breath testing and hence its apparent effect on crashes may partially represent an indirect effect of the increased testing.

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