BICYCLE CRASH STUDY COULD GUIDE DESIGN OF BICYCLIST DETECTION

©Volvo Car Group

March 31, 2015

Volvo is among a handful of automakers already adding bicyclist detection capabilities to their crash avoidance system.

A growing number of vehicles are equipped with front crash prevention technology that can recognize the back of another vehicle and prevent a rear end crash. If more of these systems could also recognize the backs of bicycles and bicyclists, they could prevent or mitigate a large portion of the crashes that kill people traveling on two wheels.

More than 3,300 bicyclists were killed in crashes in a five year period from 2008 to 2012. IIHS researchers, in a new study of bicyclist crash types relevant to the design of crash prevention systems, found that seventy-four percent of those deaths occurred when the bicyclist was struck by the front of a passenger vehicle. Of those crashes, the most common scenario accounting for 23 percent of the fatalities involved a vehicle traveling in the same direction as a bicycle and hitting it from behind. In contrast, pedestrian fatalities most commonly result from being struck while crossing a roadway

The most common configuration among all bicycle crashes, fatal and nonfatal, was a bicycle crossing the path of a straight moving vehicle. That scenario was the second most common among bicyclist fatalities involving the front of a passenger vehicle, accounting for 22 percent of deaths.

The third most common fatal scenario involved a vehicle moving straight and a bike moving against traffic. Crashes involving turning vehicles and bicycles either crossing traffic or moving in line with traffic were the second and third most common crashes, respectively, but were not among the most common fatal crash scenarios.

The study was based on information on crashes from two federal databases, the Fatality Analysis Reporting System, a census of all fatal crashes, and the National Automotive Sampling System General Estimates System which is a nationally representative sample of police reported crashes.

Compared with the total number of people who die on the nation’s roads, the number of bicyclists killed in crashes with motor vehicles is small, but it has been going up since 2010 when 621 were killed. In 2013, the last year for which data are available, the toll was 741.

“Biking has been enjoying a resurgence in recent years as individuals and local governments seek a greener form of transportation that doesn’t contribute to traffic congestion,” says David Zuby, IIHS executive vice president and chief research officer. “The auto industry should keep bicyclists in mind as it continues to develop crash avoidance technology.”

So far, most efforts to improve bicyclist safety have focused on infrastructure. Cities have added bike lanes and cycle tracks and have delineated bike boxes at intersections to give bicyclists their own space to wait for a light to change. In many cases, safety was found to improve after such changes.

But even with improved infrastructure, it would be impossible to eliminate all conflicts between vehicles and bicycles. That’s why it’s important to incorporate bicyclist detection into front crash prevention systems.

Addressing the most frequent deadly crash scenario, a vehicle striking a bicyclist from behind requires relatively minor modifications to current front crash prevention systems. They are typically designed to prevent front into rear crashes between vehicles.

Adding the capability to identify bicyclists to these systems could prevent or mitigate up to 17 percent of fatal bike crashes and up to 6 percent of all bike crashes.

Preventing crashes with bicyclists crossing traffic is more complex and has similar requirements to pedestrian detection systems which must identify people as they step in front of the vehicle from the side of the road.

A handful of automakers are already adding bicyclist detection to their crash avoidance systems. Volvo and Subaru say their optional forward collision warning and automatic braking systems recognize bicyclists as well as pedestrians.

BMW’s Night Vision is designed to detect bicyclists, pedestrians and large animals in the dark and highlight them on a display issuing an audible warning if necessary. All these systems have certain limitations, and it’s not clear what percentage of bike crashes they actually prevent or mitigate.

The new study estimates the number of crashes that could potentially be addressed. Systems designed with the three most common deadly crash scenarios in mind have the potential to help mitigate or prevent up to 26 percent of bicycle crashes and 36 percent of fatal crashes.

Systems that also address the remaining two most common crash modes could help mitigate or prevent up to a total of 47 percent of crashes and 38 percent of fatal crashes.

In addition to crash configurations, the study also looked at vehicle speed and time of day. Half of fatal crashes and nearly a quarter of all crashes involving the front of a vehicle occurred at night or during twilight.

Most crashes occurred on roads with speed limits of less than 40 mph, but only about a third of fatal ones did. Currently, not all front crash prevention systems are effective
in darkness or at high speeds, but they would need to be to have the biggest effect on bicyclist crashes and fatalities.


PEDESTRIANS AND BICYCLISTS

Roadway improvements have been shown to reduce crashes

Pedestrian deaths have declined steeply but still comprise more than a tenth of crash fatalities. The decrease may be connected to a decline in walking in recent decades. Two percent of people killed in motor vehicle crashes are bicyclists.

Traffic engineering improvements can reduce pedestrian crashes. Separating vehicles and pedestrians by installing sidewalks, overpasses and underpasses can help reduce conflicts. Other solutions include building median refuge islands and adjusting traffic signals to create an exclusive pedestrian phase or to give pedestrians a head start before vehicles get a green light.

Crash avoidance features and other vehicle improvements may also make pedestrians and bicyclists safer. Some forward collision avoidance systems are designed to detect pedestrians in a vehicle’s path, and rear cameras and other park assist systems may prevent back over crashes. Modifying the front structures of vehicles may reduce the severity of pedestrian injuries. Regulators in Europe and elsewhere have been encouraging pedestrian safety in vehicle design through their vehicle testing programs.

Helmets provide critical protection for bicyclists. Among a majority of bicyclists killed in crashes, head injuries are the most serious injuries. Helmet use has been estimated to reduce the odds of head injury by 50 percent.

Each year about 2 percent of motor vehicle crash deaths are bicyclists. In a majority of bicyclist deaths the most serious injuries are to the head, highlighting the importance of wearing a bicycle helmet. Helmet use has been estimated to reduce the odds of head injury by 50 percent, and the odds of head, face, or neck injury by 33 percent. Twenty-one states and the District of Columbia have helmet use laws applying to young bicyclists. None of these laws applies to all riders. Local ordinances in a few states require some or all bicyclists to wear helmets.

A nationwide telephone survey estimated that state helmet use laws increase by 18 percent the probability that a rider will wear a helmet. Helmets are important for riders of all ages, not just young bicyclists. Eighty-four percent of bicycle deaths are persons 20 and older. During the past few years, no more than 17 percent of fatally injured bicyclists were wearing helmets.

 

 


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