“Bicyclist Safety on US Roadways: Crash Risks and Countermeasures”
The National Transportation Safety Board (NTSB) published a recent report to bring society up to speed regarding its interpretation of bicyclists' safety in the United States. While increased access to bicycles and reliance on them as a main mode of transportation brings numerous positives to the community, such as awareness of cyclists’ rights on the roadway, unfortunately it also brings serious negatives such as heightened rates of serious personal injuries and deaths of bicyclists.
The report cites that “since 2017, 806 bicyclists died in collisions with motor vehicles which was comparable to the amount of deaths resulting from railroad and marine incidents.” The NTSB found that analyzing bicyclist fatality data and non-fatal injury estimates was insightful in looking at bicyclist safety problems relative to other transportation modes. The information also served as an indication of bicycle safety issues as well as the need for other safety correctives. These shocking figures and trends forced the NTSB to take a closer look at data behind bicyclists safety and to address three specific areas impacting bicycle safety in its report: (1) improving roadway infrastructure, (2) enhancing conspicuity and (3) mitigating head injury, which are explored further below.
Improving Roadway Infrastructure for Bicyclists
The NTSB defined a bicycle facility as “any infrastructure improvement that facilitates the safe use of bicycles as one mode of transportation among others.” In the US, familiar bicycle facilities used to accommodate bicycle traffic and improve safety range from paved shoulders, wide outside traffic lanes, bicycle-compatible drainage grates, maintenance hole covers and paved riding surfaces. Some regions have more advanced bicycle facilities to help reduce collisions in high crash locations such as separated bicycle lanes and intersection treatments.
To understand what, if any, the roadways infrastructure role played in bicycle collisions with motor vehicles, the NTSB analyzed bicycle crash statistics in terms of injury severity relative to crash location. The NTSB predictably found that a majority of motor vehicle versus bicycle collisions occurred at intersections. However, the data interestingly showed that the severity of bicycle collisions increased substantially at midblock locations. For instance, of the 173,000 motor vehicle versus bicycle collisions reported in 2014-2016, 103,000 involved nonfatal bicyclist injuries at intersections. Of the 2,410 fatal bicycle collisions reported during the same period, 1,361 or 56%, of the fatalities occurred at midblock locations. The data revealed motor vehicles speed at mid-block locations tends to be higher compared to an intersection where there are traffic control devices manage vehicular traffic and in turn reduce cars speed with traffic lights, stop signs and turn lanes.
In assessing ways to improve roadway infrastructure to reduce the most serious bicycle crashes the NTSB found separated bike lanes proved effective but were an underutilized bicycle facility. Separated bike lanes are a bicycle facility that is designed for the sole and exclusive use of bicyclists. Separated bike lanes are typically adjacent to the roadway but are physically separated from vehicular traffic by some vertical element such as a raised median, a bollard or on-street parking.
“Many European countries, specifically the Netherlands and Denmark, have been using separated bike lanes for decades and are among the safest bicycling facilities. Cities like Amsterdam and Copenhagen have been recognized as the most bicycle-friendly cities, with more than 30% of yearly trips in these cities being completed by bicycle.” While there is no bicycle lane inventory system in the US, data shows that local US agencies have begun to install separated bike lanes in recent years. Between “2008 and 2017, more than 80 miles of separated bike lanes were constructed.” Data also indicates that there are “130 bike lane projects planned or under construction that are expected to be completed between 2018 and 2022.” Department of Transportation representatives suggest that implementing separated bike lanes in our communities if often a slow process due to lack of local commitment and policies that appropriate funding to the initiative. As of 2018, 35 state Department of Transportations reported recommending separated bike lanes during the planning and design phase of their state roadway projects, however only four states actually followed through had separated bike lanes installed along their roadways. According to another database of separated bike lanes, “only 82 US cities have at least one separated bike lane.”
Research on separated bike lanes in the United States has been limited and in turn yielded mixed results. For example, in “2014, a study of separated bike lanes conducted in five US cities—Austin, Texas; Chicago, Illinois; Portland, Oregon; San Francisco, California; and the District of Columbia—found that installing separated bike lanes increased bicycle ridership and bicyclist compliance with intersection rules.” In other countries such as Montreal, Canada a study found that, compared to roads with similar characteristics, bicyclists on roads with separated bike lanes had “28% less injury risk.” A separate study in Toronto and Vancouver, focused on injuries at non-intersection locations and found that bicyclists had a “95% less chance of being injured when traveling on separated bike lanes.”
Based on the NTSB’s research, another benefit realized of separated bike lanes was that they eliminate three key bicycle crashes: rear-end collisions, overtaking and sideswipes. The NTSB concluded that separated bike lanes could prevent bicycle crashes involving motor vehicles at midblock locations and in turn also reduce the number of fatalities and serious injuries associated with such crashes.
Although separated bike lanes can improve safety for bicyclists by reducing the chance of traffic conflicts between bicycles and motor vehicles, ultimately the lanes come to intersections where potential collisions are unavoidable. “65% of nonfatal injuries and bicycle crashes occurred at intersections.” In 2017 crash data obtained from four states showed that “59% of bicyclists were involved in motor vehicle crashes at intersections or intersection-related locations.” Even though bicyclists struck by motor vehicles at intersections are more likely to sustain less serious or non-fatal injuries compared to those struck at midblock locations, the NTSB found the high frequency of intersection crashes demanded further assessment and evaluation.
Generally, intersection precautionary measures are intended to reduce crashes between motor vehicles and bicycles by increasing visibility and clearly signaling right-of-way using color, signage, medians, signals and pavement markings. There are also new bicycle-specific traffic-control devices at intersections such as: bicycle signal face, bicycle box, two-stage bicycle turn box, two-stage turns and refuge islands which are also known as protected intersections. The NTSB noted that combining these proven countermeasures to improve bicyclist safety at intersections and midblock locations also creates a network of safer roadways for bicyclists.
While collisions involving motor vehicles and bicycles can be reduced with improvement of roadway infrastructure by separating traffic with separated bike lanes and intersection treatments, the NTSB report also details how reduction in travel speeds where volume is high may be another effective component to bicycle safety. The NTSB found bicyclist crashes at locations with speed limits set at or above 50 mph were more than five times more likely to result in fatal or serious injuries to the bicyclists compared to locations with posted motor vehicle speed limits of 25 mph or less. Locations with posted speed limit of only of 30 to 35 mph yielded a “65% higher chance of the bicyclist sustaining a fatal or serious injury in a crash with a motor vehicle.”
One way to reduce traffic speeds is to lower speed limits. Some cities have lowered speed limits as part of a comprehensive strategy to improve pedestrian and bicyclist safety. For example, “in Boston, Massachusetts, the default speed limit was reduced from 30 mph to 25 mph in 2017, which in turn reduced the odds of vehicles exceeding 30 mph and 35 mph by 8.5% and 29.3%.” Therefore, the NTSB concluded that reducing traffic speeds alone can single handedly improve bicycle safety by reducing the likelihood of fatal or serious injury in the event of a crash.
In situations where reducing the speed limit is not possible, installation of separated bike lane could improve overall bicycle safety. The report cites to a study that recommended using separated bike lanes when the average vehicle speed exceeds 25 mph and or where the daily vehicle volume was more than 6,000. In situations where traffic volume was lower, but speeds exceeded 25 mph, the report recommends installing separated bike lanes, reducing speeds or lane reduction. Reducing the number of travel lanes or their widths, which is commonly referred to as a “road diet,” can result in both speed reductions and additional space for bicycle facilities. The NTSB concluded that the road diet is another proven safety countermeasure that both reduces traffic speeds and provides space on the roadway for the implementation of bicycle facilities, such as separated bike lanes.
Enhancing Conspicuity
Another aspect of bicycling safety that the NTSB analyzed was rider and bicycle conspicuity enhancements. While there are a variety of reasons as to why drivers and bicyclists fail to detect each other in time to prevent a collision, research showed about “45% of all bicyclist fatalities occur in dark conditions even though fewer than 20% of bicycle trips take place at night.” Improving the ability to see other road users can reduce the likelihood of collisions. Countermeasures that the NTSB analyzed involved reflective or bright clothing, adding lights or reflective materials to bikes and improving motor vehicle headlights to improve bicycle visibility on the roadways.
Studies show that drivers are more likely to detect bicycles and bicyclists with lights and retroreflective material and in turn reduce crashes compared to those without. Since the early 1970s efforts have been made to increase the use of conspicuity treatments among bicyclists by requiring the use of reflectors, bicycle lights at night and retroreflective upper body apparel. However, there is less evidence to show whether efforts to increase visibility have been successful. For example, an “Australian study found that while bicyclists report awareness of the benefits of using conspicuity aids, only a few of them regularly use lights or reflective clothing.” Another study of data from 2014 through 2016 found that “1,209 bicyclists were fatally injured at night. Among the 911 bicyclists with known safety equipment information, 63, or 6.9%, were identified as having bicycle lights, and 26, or 2.9%, wore reflective clothing.” The NTSB determined that riders often overestimate their level of conspicuity to other road users. Further that due to the challenges inherent in increasing rider use of conspicuity treatments, materials actually included on the bicycle at the time of manufacture may be the most reliable bicycle-conspicuity enhancement for most riders.
The risk of a bicyclist fatality which increases substantially in darkness is unfortunately a risk that is well known and understood today. Understanding the significant risk that riding in darkness poses, the NTSB criticizes the current Federal Motor Vehicle Safety Standard for headlights which does not include a minimum illumination distance or on-vehicle performance. The NTSB found manufacturers were able to self-certify that their lights met criteria for bulb output by only using results from parts that have been removed from a vehicle. Further the Department of Transportation only requires a low and high beam light and does not allow for vehicles to continuously adjust the light pattern and provide high-beam illumination. The NTSB recommends that safety standards should allow for advance vehicle lighting systems along with on-vehicle headlight testing to account for headlight height and lighting performance which would likely result in headlights that improve drivers’ ability to detect other road users like bicyclists.
A recent development in motorized vehicles technology relative to conspicuity is the design of intelligence systems within the vehicle that allow cars to detect or see obstacles in the environment. This technology was originally meant for other vehicles on the roadway however the technology has evolved to include detection of other roadway users, such as bicyclists and pedestrians. The two types of systems are collision avoidance systems (CASs) and connected technologies, both of which can reduce crashes and injuries by providing advanced warnings to the driver before they occur.
Collision avoidance systems involve a camera, radar and sensors to detect potential conflicts such as slow-moving or stopped vehicles. When a conflict is identified, the system provides warnings and ultimately may initiate an emergency braking or braking force if the driver brakes too late or not strongly enough. Connected technologies allow vehicles to communicate with one another, road infrastructure or road users to help warn of risks and crashes. Vehicle-to-pedestrian (V2P) systems are also used to describe communications between vehicles and bicyclists through electronic devices to send and receive information about the movement of transportation system users with the goal of preventing collisions. V2P systems can alert both the driver and the bicyclist which may increase the likelihood that an action may be taken to avoid a collision. While CAS and connected technologies have great potential to reduce and mitigate bicycle injuries and collisions the NTSB recommends that CAS and connected technologies could be modified to specifically detect bicycles. The NTSB noted that unfortunate delays related to the development of both technologies within the National Highway Traffic Safety Administration as well as the US Department of Transportation have slowed the development of further implementation of lifesaving technology.
While neither CASs or blind spot detection systems are currently required on large trucks and buses, NTSB research suggests these larger vehicles would especially benefit from similar onboard systems and equipment to help compensate for their larger blind spots that make it difficult for drivers to detect and maneuver around bicyclists. Such systems and equipment could include enhanced mirror systems or sensors that can alert drivers if there is another vehicle, bicyclist, or pedestrian in the blind spot after the driver activates the turn signal. The NTSB analyzed date from 2014 through 2017 and found that “511 bicyclists were involved in crashes involving transit operations. Among them, 374 bicyclists, or 73%, collided with transit buses. Twenty-three bicyclists, or 6%, died in these crashes.” The NTSB concluded there needs to be continued performance standards to ensure blind spot detection systems can detect vulnerable road users, including bicyclists.
Mitigating Head Injury
Improving roadway infrastructure, motor vehicle headlights, and in-vehicle collision avoidance systems can prevent bicycle crashes involving motor vehicles. Bicyclists can also reduce the likelihood of getting in a crash by obeying traffic rules and traffic controls, such as traffic signals, and enhancing conspicuity, such as using bicycle lights. In analyzing actual bicyclist injuries, the NTSB found head injury to be the leading cause of bicycle-related deaths. Bicyclists involved in motor vehicle collisions are more likely to sustain a higher percentage of head injuries compared to other injuries. In the unfortunate event that a crash does occur the NTSB remarked, the most effective method for a bicyclist to mitigate head injury is to properly wear a bicycle helmet that is compliant with the federal safety standard for bicycle helmets.
The NTSB examined data from 2014 through 2017 and found that “only 15% of crashes between motor vehicles and bicycles indicated whether the bicyclist was or was not wearing a helmet.” These cases represented about 60,000 bicyclists. “The 60,000 bicyclists were divided into four categories based on helmet use and head injury. Thirty-five percent of the bicyclists were wearing a helmet and among them, 24% sustained a head injury. In comparison, 65% of the roughly 60,000 bicyclists were not wearing a helmet and 36% of them sustained a head injury.” This data suggests that among all bicyclists involved in crashes with motor vehicles with known helmet use, those wearing helmets had a considerably lower chance of sustaining a head injury.
Although there is strong and consistent evidence demonstrating the effectiveness of helmets for protecting bicyclists from head injuries during bicycle-related crashes, helmet use in the United States remains low. “In 2012, based on a nationally representative sample, published by the National Survey of Bicyclist and Pedestrian Attitudes and Behavior results showed only 28% of respondents reported that they always wore a helmet when riding a bicycle and 46% of respondents reported that they never wore a helmet.” In a separate study conducted from 2010 to 2017, helmet usage in collisions were measured by age group. Among fatally injured bicyclists, “the groups least likely to be wearing a helmet were those between the ages of 15 and 19 (94%) and those between the ages of 10 and 14 (92%).” The groups least likely to be wearing a helmet in a non-fatal collision were those “under the age of 10 (76%) and those between the ages of 20 and 24 (74%).” This data shows that helmet use among bicyclists is low overall, especially amongst children and young adults. The NTSB concluded that the underutilization of bicycle helmets has contributed to the incidence of deaths and serious injuries among crash-involved bicyclists.
