The potential of vehicle and road infrastructure interventions in fatal bicyclist accidents on Swedish roads-What can in-depth studies tell us?

Objective: The objective of this article is to describe the characteristics of fatal crashes with bicyclists on Swedish roads in rural and urban areas and to investigate the potential of bicycle helmets and different vehicle and road infrastructure interventions to prevent them. The study has a comprehensive approach to provide road authorities and vehicle manufacturers with recommendations for future priorities. Methods: The Swedish Transport Administration's (STA) in-depth database of fatal crashes was used for case-by-case analysis of fatal cycling accidents (2006-2016) on rural (n = 82) and urban (n = 102) roads. The database consists of information from the police, medical journals, autopsy reports, accident analyses performed by STA, and witness statements. The potential of helmet use and various vehicle and road infrastructure safety interventions was determined retrospectively for each case by analyzing the chain of events leading to the fatality. The potential of vehicle safety countermeasures was analyzed based on prognoses on their implementation rates in the Swedish vehicle fleet. Results: The most common accident scenario on rural roads was that the bicyclist was struck while cycling along the side of the road. On urban roads, the majority of accidents occurred in intersections. Most accidents involved a passenger car, but heavy trucks were also common, especially in urban areas. Most accidents occurred in daylight conditions (73%). Almost half (46%) of nonhelmeted bicyclists would have survived with a helmet. It was assessed that nearly 60% of the fatal accidents could be addressed by advanced vehicle safety technologies, especially autonomous emergency braking with the ability to detect bicyclists. With regard to interventions in the road infrastructure, separated paths for bicyclists and bicycle crossings with speed calming measures were found to have the greatest safety potential. Results indicated that 91% of fatally injured bicyclists could potentially be saved with known techniques. However, it will take a long time for such technologies to be widespread. Conclusions: The majority of fatally injured bicyclists studied could potentially be saved with known techniques. A speedy implementation of important vehicle safety systems is recommended. A fast introduction of effective interventions in the road infrastructure is also necessary, preferably with a plan for prioritization.

Influence of crash pulse characteristics on injury risk in frontal impacts based on real-life crashes.

OBJECTIVES: In single-vehicle car crashes with roadside objects, one way to achieve low acceleration is to allow long duration by making objects more flexible. There is a lack of knowledge regarding the influence of long pulse duration on injury risk. The objectives were to study the influence of crash pulse characteristics on injury risk in frontal impacts and to study the correlation of these crash pulse characteristics, especially including crash pulse duration. Furthermore, the objective was to study crash pulse characteristics in crashes with various types of guardrails. METHODS: To study the influence of crash pulse duration on injury risk, data from 448 real-life frontal collisions with recorded crash pulses were used and a subgroup of 37 guardrail crashes was analyzed. The inclusion criteria were repair cost and impact angle. Five hundred seventy-eight restrained occupants were included. Injury risk, correlation, and sensitivity analyses were made for the various crash pulse characteristics. RESULTS: It was found that the duration has a limited influence on injury risk. Change of velocity and mean and peak acceleration were found to influence injury risk and they were also well correlated. The correlation between mean acceleration and pulse duration was low. Crashes into cable barriers were found to have lower acceleration than crashes into w-beam and concrete barriers. The difference in mean acceleration between the most and less severe barrier crash was smallest in crashes with cable barriers. CONCLUSIONS: Long duration of the crash pulse does not lead to high injury risk as long as the mean and peak acceleration are low. In the design of cars and roadside objects the main design criteria should be acceleration and not delta V, due to the findings that long duration could be handled.

Risk of permanent medical impairment (RPMI) in road traffic accidents.

In addition to investigating risk of death due to road traffic injuries, there is a need to better describe the risk of serious consequences. This study assessed risk of permanent medical impairment based on road traffic injuries classified according to AIS-2005. Injured car occupants were followed for at least 5 years to assess permanent medical impairment. After an initial injury, the risk of permanent impairment was established for injuries to different body regions and AIS levels. Degree of impairment was assessed according to a manual used by all Swedish insurance companies. Those included in the study were 20,484 car occupants injured in crashes that occurred between 1995 and 2001. Three risk levels of sustaining a permanent medical impairment (RPMI) were made. It was concluded that almost 10% of all car occupants with AIS1 injuries sustained a permanent medical impairment. It is therefore important to include minor injuries leading to impairment when measuring loss of health due to road traffic crashes. Furthermore the highest risk of sustaining a permanent medical impairment from an AIS1 injury was associated with injuries to the cervical spine and upper and lower extremities. One third of AIS3 head and cervical spine injuries led to the highest RPMI level of impairment. Injuries to the thorax and abdomen gave the lowest risk of permanent medical impairment on all AIS levels and all impairment levels. The result can be used for road transport system strategies, and for making priority decisions in vehicle design.