Evaluation of the Bicycle Helmet Wearing Law in Victoria during its First Four Years

Monash University Accident Research Centre - Report #76 - 1995

Authors: D. Carr, M. Skalova & M.H. Cameron

Full report in .pdf format [2.4MB]

Abstract:

This research project evaluated the effect of the mandatory bicycle helmet wearing legislation which was introduced in Victoria in 1990, using data from the Hospital Admissions database which includes data for all bicyclists admitted to a public hospital after a crash. The project built on earlier work conducted by the Monash University Accident Research Centre, and in particular on Newstead, Cameron, Gantzer, & Finch (1994).

Newstead et al. analysed bicyclist injury data for the first three years of mandatory helmet wearing and reported conflicting results which suggested the effects of the helmet wearing legislation may have declined in the third year. Preliminary analyses of the hospital admissions data in the current project suggested the apparent increase in bicyclist admissions to hospital in the third and fourth years after the legislation was most likely the result of changes in the funding arrangements for publicly funded hospitals. The bicyclist data in the hospital admissions database were corrected to remove this effect.

Multivariate time series analyses of the corrected number of bicyclist admissions to hospital in Victoria indicated admissions in the first four years of the helmet legislation were 40% below the number expected on the basis of pre-legislation trends. The inclusion of other road-safety related factors in the modelling process suggested the reduction in bicyclist admissions was largely due to the helmet legislation. Analysis of the severity of head injuries for crash-involved bicyclists similarly indicated the severity of head injuries has declined after the introduction of the helmet wearing legislation.

It was concluded that the mandatory helmet wearing legislation has had a significant, positive effect on the number and severity of injuries amongst bicyclists, and that this effect has persisted for the four years since the introduction of the legislation.

Executive Summary

Introduction

Legislation requiring the use of a helmet while riding a bicycle was introduced in Victoria in July 1990. The purpose of the legislation was the reduction of both number and severity of head injuries through increased use of bicycle helmets by all age groups.

Surveys of bicycle helmet use have shown that post-legislation wearing rates were significantly greater than pre-legislation rates in all age groups (Finch, Heiman, & Neiger, 1993), although Finch et al. (1993) reported that the introduction of the legislation was accompanied by reduced bicycle use in the first year for all age groups, especially teenagers. Bicycle use by teenagers and younger children remained lower than pre-legislation levels in the second year while bicycle use by adults increased.

The reported increase in helmet wearing rates ( and the apparent reduction in exposure to crashes through reduced bicycle use) leads to the expectation that the number of bicyclists presenting with crash-related head injuries has declined since 1990, as has the severity of bicyclist head injuries.

In the first two years of the legislation, the number and proportion of head injuries amongst hospitalised bicyclists declined (Cameron, Vulcan, Finch, & Newstead, 1994). An evaluation of the first three years of helmet legislation, however, reported conflicting data (Newstead, Cameron, Gantzer, & Finch, 1994) indicating an increase in the number and proportion of hospitalised cyclists sustaining head injuries in crashes involving a motor vehicle during the third year.

The aim of this report was to present a thorough analysis of the effects of the first four years of helmet legislation.

Data Problems

Newstead et al. (1994) noted some differences between the two data sources used in their study - the Hospital Admissions data based on Health Department records of admissions to public hospitals, and the claims data from the Transport Accident Commission which is responsible for “no-fault” injury compensation in the case of crashes involving motor vehicles. In addition there was also an apparent increase in head injuries in the third year of the legislation.

The numbers and proportions of head injured victims of crashes in each data base from 1987/88 to 1993/94 were examined, and it was concluded that a substantial part of the apparent increase in head injuries amongst crash-involved bicyclists related to a change in admissions policy in the Victorian hospital system (Casemix Funding), resulting from the use of incentives for hospitals based on their throughput and the number of injuries treated.

Data Analysis Technique

Multivariate time-series techniques were used to model the changes in the number of head-injured bicyclists. The changing level of injury severity was taken into account.

Data from the Hospital Admissions database were used in the analyses, but were corrected for the possible (effects of Casemix Funding. It was noted that the relative rate of head injury for all hospital admissions had increased markedly since the 1992/93 financial year (from 87/88 to 92/93 the numbers were more or less constant) and this overall increase was used as a correction factor in the time series analysis of the bicyclist head injury data.

Number of Head-Injured Bicyclists

Time series models of the number of bicyclists admitted to hospital with head injuries indicated that the helmet wearing legislation has had a substantial impact. It was estimated from these models that the first four years of this legislation has seen a (statistically reliable) 42% reduction in the number of head-injured admissions across Victoria.

The inclusion of other possible contributory factors in the modelling process suggests that the change is largely due to the introduction of the mandatory helmet wearing legislation, although it is possible that a part of the change relates to the reduced exposure to crash risk of bicyclists since the legislation’s introduction.

Injury Severity

Investigation of the levels of head injury severity of bicyclists admitted to hospital similarly indicated that the legislation has had an impact. The proportion of admitted bicyclists with the (critical) head injury severity remained unchanged in the post-legislation period, but there were clear reductions in the proportion of admitted bicyclists with head injuries in the serious and severe categories. The proportion of bicyclists in with head injuries in these severity categories declined by 40% (all admitted bicyclists) and 46% (admitted bicyclists where a motor-vehicle was involved in the crash).

Conclusions

The detailed analysis of the data relating to bicyclist head injuries presented in this report indicates that the mandatory helmet wearing legislation has had a significant, positive impact on both the number of head-injured bicyclists and on the severity of injuries for bicyclists admitted to hospital. These changes have continued through the first four years post-legislation and are apparent in spite of recent anomalies in the Hospital Admissions data.

Sponsoring Organisation: Baseline Research Program - Department of Justice, Transport Accident Commission, Royal Automobile Club of Victoria (RACV) Ltd, VicRoads