Analysis of Trends in Motorcycle Crashes in Victoria

Monash University Accident Research Centre - Report #84 - 1995

Authors: K. Diamantopoulou, I. Brumen, D. Dyte & M. Cameron

Abstract:

This study has analysed trends in motorcycle casualty crashes in Victoria for the period 1984-1993 in two stages.

Stage 1 examined the trends in Police-reported motorcycle crashes resulting in death or injury in Victoria during 1984-1993. It was found that the trend in motorcycle casualty crashes was different from that for all reported casualty crashes in Victoria since 1989, with the proportion of motorcycle crashes generally increasing since that year.

Stage 2 compared the Victorian trends found in Stage 1 with trends in motorcyclist casualties and casualty crashes obtained from other data sources and jurisdictions. This included a comparison of Victorian motorcyclist fatalities with those in Australia as a whole; a comparison of motorcycle casualty crash trends found in Stage 1 for Victoria with trends in Police-reported casualty crashes in New South Wales during 1984-93; an analysis of the trends in numbers of motorcyclists recorded as admitted to public hospitals in Victoria during the financial years 1987/88 to 1992/93 and a comparison of the numbers of and trends in seriously injured motorcyclists on Police reports with those admitted to Victorian public hospitals during the years 1987/88 to 1992/93.

The two stages of this study are bound together in this publication.

CONCLUSION (STAGE 1)

Stage 1 of the Motorcycle Research Project aimed to analyse trends in Police-reported motorcycle crashes in Victoria during 1984-1993. The frequency of motorcycle casualty crashes declined regularly during 1987-1993, and a significant reduction in the ratio of motorcycle casualty crashes to all casualty crashes occurred between 1984 and 1989. However, a significant increase occurred between 1989 and 1993 in the motorcycle to all vehicle casualty crash ratio. The increase observed in fatal motorcycle crashes during 1991-1992 was not statistically significant.

The decrease in motorcycle casualty crashes over the ten year period was primarily for crashes that occurred in low speed zones. High speed zone crashes showed no such reduction. There has been a progressive decrease in multi-vehicle motorcycle crashes during 1984-1993, whereas only a marginal decrease occurred in single-vehicle motorcycle crashes from 1990 onwards. The reduction that occurred in multi-vehicle motorcycle crashes was primarily due to the crashes that occurred in low Victorian speed zones (75km/h or lower). The progressive reduction in multi-vehicle crashes involving motorcycles in lower speed zones warrants further investigation.

Motorcycle crashes were more severe than all crashes. Up to 50% of motorcycle casualties were fatal or severe injuries, compared with 35% for all crashes. Furthermore in Victoria, motorcycle riders killed or seriously injured were less likely to have excessive BAC readings above 0.15g/100ml than other drivers during 1984-1993. It should be noted however, that the proportion of seriously injured riders with unknown BAC readings increased substantially after 1989. This is likely to be due to the changes in 1989 in the practice of taking blood samples in hospitals to determine alcohol concentration.

Motorcycle rider casualties were predominantly male throughout the ten-year period, whereas female pillion passenger casualties exceeded those of males after 1991.

A consistent decline in motorcycle casualties occurred for persons aged 25 years and below during 1984-1993, whereas those riders aged over 37 years showed a steady increase. The number of motorcycle casualties for under-age riders and pillion passengers also dropped after 1989. A sharp decrease in probationary licence holder casualties occurred by 1989 and remained constant thereafter, whereas unlicensed rider casualties declined steadily throughout the ten-year period.

ANALYSIS OF TRENDS IN MOTORCYCLE CRASHES IN VICTORIA (STAGE 2)

Executive Summary

This is the second of two reports which examine trends in motorcycle crashes and injuries reported to the Police in Victoria. This report compares these trends with trends in motorcyclist fatalities throughout Australia, motorcycle crashes and injuries in New South Wales, and motorcyclist hospital admission records in Victoria. A comparison of numbers of seriously injured motorcyclists recorded in Police report files and in hospital admission records is also made in this report.

First Report

The first report examined trends in Police-reported motorcycle crashes resulting in death or injury in Victoria during 1984-93. It was found that the trend in motorcycle casualty crashes was different from that for all reported casualty crashes in Victoria since 1989, with the proportion of motorcycle crashes generally increasing since that year. The number of motorcycle casualty crashes in Victoria has decreased even since 1987, but at a slower rate than casualty crashes generally. Further details are given in the Stage 1 Report (Diamantopoulou, Dyte and Cameron 1995) which should be read as a companion document to this report.

Comparison with motorcyclist fatalities throughout Australia

Australia-wide, it was found that the number of motorcyclists killed during 1984-93 had decreased more rapidly than in Victoria. In New South Wales in particular, the proportion of fatal crashes involving motorcycles had been halved, compared with essentially no change in Victoria.

Comparison with motorcycle crashes and injuries in New South Wales

In Victoria, the decrease in motorcycle casualty crashes was primarily multi-vehicle crashes occurring in low speed zones of 75 km/h or lower, whereas in New South Wales, the decline in motorcycle casualty crashes was in both low and high speed zones, and in both single- and multi-vehicle crashes.

Reliable information on blood alcohol concentration (BAC) levels was available only for motorcycle riders who were killed. In New South Wales, the proportion of killed riders with excessive BAC readings (above 0.15 g/100ml) increased substantially during 1984-93, whereas in Victoria, the proportion was more than halved during 1989-93.

Both States were consistent in showing the greatest decreases in motorcyclist casualties among those aged under 26 years, whilst those aged over 37 years showed an increasing trend in deaths and injuries.

Trends in motorcyclist hospital admissions in Victoria

An alternative source of data on motorcyclist injuries in Victoria was public hospital admission records, available for 1987/88 to 1992/93. This data source confirmed that serious motorcyclist injuries did not reduce as rapidly as other road traffic injuries resulting in hospital admission during the period. The data also showed that for motorcyclists aged under 15 years, hospital admissions from off-road crashes were more numerous than those from crashes on-road. In other respects, the hospital admission records reflected the findings from Police reports, except that admissions eventuated from a greater proportion of single motorcycle crashes.

Comparison of data from Police reports and hospital admissions in Victoria

When the two sources of data on motorcyclist serious injuries in Victoria were compared, it was found that substantially fewer serious injuries were recorded in the database of Police crash reports held by VicRoads than were recorded as admitted to hospital. The reverse was true for serious road traffic injuries generally, probably emanating from the known practice whereby the VicRoads database records as "serious injury" many cases of injury which did not result in hospital admission. Thus providing the hospital coding of on-road/off-road motorcycle injuries is correct, the extent of under-reporting of motorcyclist hospital admissions in the database of Police crash records may be even greater than has been indicated.

Recommendations for further investigation

The principal area of improvement in motorcyclist trauma in Victoria during 1984-93 was from the reduction in multi-vehicle crashes in the low speed zones of 75 km/h or lower. Factors which may explain this improvement, in contrast with other crash types, should be investigated.
The creation of a linked file matching motorcyclists recorded on Police reports with records of motorcyclist hospital admissions would be valuable for research to understand the extent to which the admissions are reported to the Police, the extent of miscoding on the hospital database and to gain some understanding of the error in the injury severity levels recorded by both VicRoads and the Police.
For a fuller understanding of the injury recording practices used by the Police, a file linking motorcyclists recorded on Police reports would need to be linked with hospital admission records, Accident and Emergency Department (non-admission) records, and records of injury treatments by General Practitioners.

Sponsor: VicRoads