The relationship between impact speed and the probability of pedestrian fatality during a vehicle-pedestrian crash: A systematic review and meta-analysis.

BACKGROUND: Pedestrians struck in motorised vehicle crashes constitute the largest group of traffic fatalities worldwide. Excessive speed is the primary contributory factor in such crashes. The relationship between estimated impact speed and the risk of a pedestrian fatality has generated much debate concerning what should be a safe maximum speed limit for vehicles in high pedestrian active areas. METHODS: Four electronic databases (MEDLINE, EMBASE, COMPENDEX, and SCOPUS) were searched to identify relevant studies. Records were assessed, and data retrieved independently by two authors in adherence with the PRISMA statement. The included studies reported data on pedestrian fatalities from motorised vehicle crashes with known estimated impact speed. Summary odds ratios (OR) were obtained using meta-regression models. Time trends and publication bias were assessed. RESULTS: Fifty-five studies were identified for a full-text assessment, 27 met inclusion criteria, and 20 were included in a meta-analysis. The analyses found that when the estimated impact speed increases by 1 km/h, the odds of a pedestrian fatality increases on average by 11% (OR = 1.11, 95% CI: 1.10-1.12). The risk of a fatality reaches 5% at an estimated impact speed of 30 km/h, 10% at 37 km/h, 50% at 59 km/h, 75% at 69 km/h and 90% at 80 km/h. Evidence of publication bias and time trend bias among included studies were found. CONCLUSIONS: The results of the meta-analysis support setting speed limits of 30-40 km/h for high pedestrian active areas. These speed limits are commonly used by best practice countries that have the lowest road fatality rates and that practice a Safe System Approach to road safety.

The impact of bicycle helmet legislation on cycling fatalities in Australia.

BACKGROUND: Australian bicycle helmet laws were first introduced in Victoria in July 1990 and the remaining Australian states, Australian Capital Territory and Northern Territory by July 1992. Previous research on helmet legislation has focused on changes in helmet wearing and bicycle-related head injury. Although it is generally accepted that bicycle helmets can reduce the risk of fatality due to head injury, there has been little research assessing the impact of helmet legislation on cycling fatalities. METHODS: An interrupted time series approach was used to assess the impact of bicycle helmet legislation on yearly-aggregated rates of bicycle-related fatalities per population from 1971 to 2016. RESULTS: Immediately following bicycle helmet legislation, the rate of bicycle fatalities per 1 000 000 population reduced by 46% relative to the pre-legislation trend [95% confidence interval (CI): 31, 58]. For the period 1990-2016, we estimate 1332 fewer cycling fatalities (95% CI: 1201, 1463) or an average of 49.4 per year (95% CI: 44.5, 54.2). Reductions were also observed for pedestrian fatalities; however, bicycle fatalities declined by 36% relative to pedestrian fatalities (95% CI: 12, 54). CONCLUSIONS: In the absence of robust evidence showing a decline in cycling exposure following helmet legislation or other confounding factors, the reduction in Australian bicycle-related fatality appears to be primarily due to increased helmet use and not other factors.

The impact of environmental factors on cycling speed on shared paths.

BACKGROUND: Despite the importance of cycling speed on shared paths to the amenity and safety of users, few studies have systematically measured it, nor examined circumstances surrounding it. METHODS: Speed was measured for 5421 riders who were observed cycling on shared paths across 12 metropolitan and regional locations in Sydney, Australia. Multivariate regression analysis was carried out to examine rider and environmental factors that contribute to riders cycling above the median speed. RESULTS: The study found that observed riders travelled at a median speed of 16km/h (mean 18.4km/h). Nearly 80% of riders travelled at 20km/h or less and 7.8% at speeds of more than 30km/h. Riders were significantly less likely to cycle above the median speed on shared paths that had an average volume of over 20 pedestrians/hour. Riders were significantly more likely to travel above the median speed on paths that had a centreline (OR: 1.71, 95% CI: 1.41-2.07), on wider paths (over 3.5m) (OR: 1.34, 95% CI: 1.12-1.59) and on paths with visual segregation between cyclists and pedestrians. Visual segregation, where cycling and walking areas are differentiated by the type of material or by paint colour used, was the strongest predictor of travelling above median speed on shared paths (OR: 3.9, 95% CI: 3.1-4.8). CONCLUSIONS: The findings suggest that riders adjust their speeds to accommodate pedestrians and path conditions. Path characteristics that support separation from pedestrians may allow relatively higher speeds, and associated amenity, without substantial loss of safety.

Capture and surveillance of quad-bike (ATV)-related injuries in administrative data collections.

Identifying quad-bike-related injuries in administrative data collections can be problematic. This study sought to determine whether quad-bike-related injuries could be identified in routinely collected administrative data collections in New South Wales (NSW), Australia, and to determine the information recorded according to World Health Organization (WHO) injury surveillance guidelines that could assist injury prevention efforts. Five routinely collected administrative data collections in NSW in the period 2000-2012 were reviewed. The WHO core minimum data items recorded in each of the five data collections ranged from 37.5% to 75.0%. Age and sex of the injured individual were the only data items that were recorded in all data collections. The data collections did not contain detailed information on the circumstances of quad bike incidents. Major improvements are needed in the information collected in these data-sets, if their value is to be increased and used for injury prevention purposes.

Factors that influence chest injuries in rollovers.

OBJECTIVES: The design of countermeasures to reduce serious chest injuries for belted occupants involved in rollover crashes requires an understanding of the cause of these injuries and of the test conditions to assure the effectiveness of the countermeasures. This study defines rollover environments and occupant-to-vehicle interactions that cause chest injuries for belted drivers. METHODS: The NASS-CDS was examined to determine the frequency and crash severity for belted drivers with serious (Abbreviated Injury Scale [AIS] 3+) chest injuries in rollovers. Case studies of NASS crashes with serious chest injuries sustained by belted front occupants were undertaken and damage patterns were determined. Vehicle rollover tests with dummies were examined to determine occupant motion in crashes with damage similar to that observed in the NASS cases. Computer simulations were performed to further explore factors that could contribute to chest injury. Finite element model (FEM) vehicle models with both the FEM Hybrid III dummy and THUMS human model were used in the simulations. RESULTS: Simulation of rollovers with 6 quarter-turns or less indicated that increases in the vehicle pitch, either positive or negative, increased the severity of dummy chest loadings. This finding was consistent with vehicle damage observations from NASS cases. For the far-side occupant, the maximum chest loadings were caused by belt and side interactions during the third quarter-turn and by the center console loading during the fourth quarter-turn. The results showed that the THUMS dummy produced more realistic kinematics and improved insights into skeletal and chest organ loadings compared to the Hybrid III dummy. CONCLUSIONS: These results suggest that a dynamic rollover test to encourage chest injury reduction countermeasures should induce a roll of at least 4 quarter-turns and should also include initial vehicle pitch and/or yaw so that the vehicle's axis of rotation is not aligned with its inertial roll axis during the initial stage of the rollover.

Are drivers aware of sleepiness and increasing crash risk while driving?

Drivers are advised to take breaks when they feel too tired to drive, but there is question over whether they are able to detect increasing fatigue and sleepiness sufficiently to decide when to take a break. The aim of this study was to investigate the extent to which drivers have access to cognitive information about their current state of sleepiness, likelihood of falling asleep, and the implications for driving performance and the likelihood of crashing. Ninety drivers were recruited to do a 2h drive in a driving simulator. They were divided into three groups: one made ratings of their sleepiness, likelihood of falling asleep and likelihood of crashing over the next few minutes at prompts occurring at 200s intervals throughout the drive, the second rated sleepiness and likelihood of falling asleep at prompts but pressed a button on the steering wheel at any time if they felt they were near to crashing and the third made no ratings and only used a button-press if they felt a crash was likely. Fatigue and sleepiness was encouraged by monotonous driving conditions, an imposed shorter than usual sleep on the night before and by afternoon testing. Drivers who reported that they were possibly, likely or very likely to fall asleep in the next few minutes, were more than four times more likely to crash subsequently. Those who rated themselves as sleepy or likely to fall asleep had a more than 9-fold increase in the hazards of a centerline crossing compared to those who rated themselves as alert. The research shows clearly that drivers can detect changes in their levels of sleepiness sufficiently to make a safe decision to stop driving due to sleepiness. Therefore, road safety policy needs to move from reminding drivers of the signs of sleepiness and focus on encouraging drivers to respond to obvious indicators of fatigue and sleepiness and consequent increased crash risk.

The impact of compulsory helmet legislation on cyclist head injuries in New South Wales, Australia: a response.

This article responds to criticisms made in a rejoinder (Accident Analysis and Prevention 2012, 45: 107-109) questioning the validity of a study on the impact of mandatory helmet legislation (MHL) for cyclists in New South Wales, Australia. We systematically address the criticisms through clarification of our methods, extension of the original analysis and discussion of new evidence on the population-level effects of MHL. Extensions of our analysis confirm the original conclusions that MHL had a beneficial effect on head injury rates over and above background trends and changes in cycling participation. The ongoing debate around MHL draws attention away from important ways in which both safety and participation can be improved through investment in well-connected cycling infrastructure, fostering consideration between road users, and adequate legal protection for vulnerable road users. These are the essential elements for providing a cycling environment that encourages participation, with all its health, economic and environmental benefits, while maximising safety.

Long term bicycle related head injury trends for New South Wales, Australia following mandatory helmet legislation.

Since the 1991 enactment of mandatory helmet legislation (MHL) for cyclists in New South Wales (NSW), Australia, there has been extensive debate as to its effect on head injury rates at a population level. Many previous studies have focused on the impact of MHL around the time of enactment, while little has been done to examine the ongoing effects. We aimed to extend prior work by investigating long-term trends in cyclist head and arm injuries over the period 1991-2010. The counts of cyclists hospitalised with head or arm injuries were jointly modelled with log-linear regression. The simultaneous modelling of related injury mechanisms avoids the need for actual exposure data and accounts for the effects of changes in the cycling environment, cycling behaviour and general safety improvements. Models were run separately with population counts, bicycle imports, the average weekday counts of cyclists in Sydney CBD and cycling estimates from survey data as proxy exposures. Overall, arm injuries were higher than head injuries throughout the study period, consistent with previous post-MHL observations. The trends in the two injury groups also significantly diverged, such that the gap between rates increased with time. The results suggest that the initial observed benefit of MHL has been maintained over the ensuing decades. There is a notable additional safety benefit after 2006 that is associated with an increase in cycling infrastructure spending. This implies that the effect of MHL is ongoing and progress in cycling safety in NSW has and will continue to benefit from focusing on broader issues such as increasing cycling infrastructure.

Exposure-based cycling crash, near miss and injury rates: the Safer Cycling Prospective Cohort Study protocol.

INTRODUCTION: There are clear personal, social and environmental benefits of cycling. However, safety concerns are among the frequently cited barriers to cycling. In Australia, there are no exposure-based measures of the rates of crash or 'near miss' experienced by cyclists. DESIGN AND SETTING: A prospective cohort study over 12 months, with all data collected via web-based online data entry. PARTICIPANTS: Two thousand adults aged 18 years and older, living in New South Wales (Australia), who usually bicycle at least once a month, will be recruited from March to November 2011. METHODS: In the 12 months following enrolment, cyclists will be surveyed on six occasions (weeks 8, 16, 24, 32, 40 and 48 from the week of the enrolment survey). In these survey weeks, cyclists will be asked to provide daily reports of distance travelled; time, location and duration of trips; infrastructure used; crashes, near misses and crash-related injuries. Information on crashes and injuries will also be sought for the intervening period between the last and current survey. A subsample of participants will receive bicycle trip computers to provide objective measurement of distance travelled. DISCUSSION: This study protocol describes the prospective cohort study developed to assess near misses, crashes and injuries among cyclists by time and distance travelled and by type of infrastructure used, with recruited participants entering data remotely using the internet. We expect to be able to calculate event rates according to exposure overall and for different infrastructure types and to report in-depth information about event causation.

The impact of compulsory cycle helmet legislation on cyclist head injuries in New South Wales, Australia.

The study aimed to assess the effect of compulsory cycle helmet legislation on cyclist head injuries given the ongoing debate in Australia as to the efficacy of this measure at a population level. We used hospital admissions data from New South Wales, Australia, from a 36 month period centred at the time legislation came into effect. Negative binomial regression of hospital admission counts of head and limb injuries to cyclists were performed to identify differential changes in head and limb injury rates at the time of legislation. Interaction terms were included to allow different trends between injury types and pre- and post-law time periods. To avoid the issue of lack of cyclist exposure data, we assumed equal exposures between head and limb injuries which allowed an arbitrary proxy exposure to be used in the model. As a comparison, analyses were also performed for pedestrian data to identify which of the observed effects were specific to cyclists. In general, the models identified a decreasing trend in injury rates prior to legislation, an increasing trend thereafter and a drop in rates at the time legislation was enacted, all of which were thought to represent background effects in transport safety. Head injury rates decreased significantly more than limb injury rates at the time of legislation among cyclists but not among pedestrians. This additional benefit was attributed to compulsory helmet legislation. Despite numerous data limitations, we identified evidence of a positive effect of compulsory cycle helmet legislation on cyclist head injuries at a population level such that repealing the law cannot be justified.

Characteristics of fatal motorcycle crashes into roadside safety barriers in Australia and New Zealand.

This paper reports on the findings of a retrospective case series study of fatal motorcyclist-roadside barrier collisions. Cases were retrieved from the National Coroners Information System (NCIS), the coronial case files of Australian jurisdictions, and the Crash Analysis System (CAS) of the New Zealand Transport Agency. Seventy seven (77) motorcycle fatalities involving a roadside barrier in Australia and New Zealand were examined. The fatalities usually involved a single vehicle crash and young men. The roadside barriers predominantly involved were steel W-beams, typically on a bend in the horizontal alignment of the road. A majority of fatalities occurred on a weekend, during daylight hours, on clear days with dry road surface conditions indicating predominantly recreational riding. Speeding and driving with a blood alcohol level higher than the legal limit contributed to a significant number of these fatalities.

Exploring differential trends in severe and fatal child pedestrian injury in New South Wales, Australia (1997-2006).

The study explores trends in severe and fatal child pedestrian injuries in New South Wales (NSW), over the 10-year period 1997-2006, in comparison to adults and for various subgroups. Data on pedestrian injury (reported as fatalities or hospitalisations) were obtained from the Traffic Accident Database System (TADS; Roads and Traffic Authority of New South Wales) which captures road traffic events reported to police, and from the NSW Admitted Patients Data Collection (APDC) which captures all hospital inpatient separations. Annual percentage changes in injury counts and rates were compared using Poisson regression. A substantial drop in the pedestrian injury rate was observed; however, the rate of decline was steeper for children (aged less than 15 years) than for adults. The drop in child pedestrian injury was manifest in both the police report data and the hospital admission data. The annual percentage decrease was significantly greater for boys than for girls, and the three major urban centres compared with elsewhere in the state. No differences were detected in the annual rate decrease between school days and non-school days (a proxy for safe school zones), or between different road types (a proxy for restricted speed limits). Past research suggests that injury rate reductions are not solely due to decreased exposure. There remains, however, limited data on the extent of pedestrian mobility. Differences in relative reduction in pedestrian injury rates suggest a differential benefit arising from road safety initiatives.

Relative injury severity among vulnerable non-motorised road users: comparative analysis of injury arising from bicycle-motor vehicle and bicycle-pedestrian collisions.

With the expansion of bicycle usage and limited funding and/or space for segregated pedestrian and bicycle paths, there is a need for traffic, road design and local government engineers to decide if it is more appropriate for space to be shared between either cyclists and pedestrians, or between cars and cyclists, and what restrictions need to be applied in such circumstances. To provide knowledge to aid engineers and policy makers in making these decisions, this study explored death and morbidity data for the state of New South Wales, Australia to examine rates and severity of injury arising from collisions between pedestrians and cyclists, and between cyclists and motor vehicles (MVs). An analysis of the severity of hospitalised injuries was conducted using International Classification of Diseases, Version 10, Australian Modification (ICD-10-AM) diagnosis-based Injury Severity Score (ICISS) and the Disability Adjusted Life Year (DALY) was used to measure burden of injury arising from collisions resulting in death or hospitalisation. The greatest burden of injury in NSW, for the studied collision mechanisms, is for cyclists who are injured in collisions with motor vehicles. Collisions between cyclists and pedestrians also result in significant injuries. For all collision mechanisms, the odds of serious injury on admission are greater for the elderly than for those in other age groups. The significant burden of injury arising from collisions of cyclists and MVs needs to be addressed. However in the absence of appropriate controls, increasing the opportunity for conflict between cyclists and pedestrians (through an increase in shared spaces for these users) may shift the burden of injury from cyclists to pedestrians, in particular, older pedestrians.