UNIT 2: ROADWAY SAFETY
page 11 of 29Bicycle Lanes
Most fatal and serious injury bicyclist crashes occur at non-intersection locations. Nearly one-third of these crashes involve overtaking motorists, the speed and size differential between vehicles and bicycles can lead to severe injury. To make bicycling safer and more comfortable for most types of bicyclists, State and local agencies should consider installing bicycle lanes. These dedicated facilities for the use of bicyclists along the roadway can take several forms. Providing bicycle facilities can mitigate or prevent interactions, conflicts, and crashes between bicyclists and motor vehicles, and create a network of safer roadways for bicycling. Bicycle Lanes align with the Safe System Approach principle of recognizing human vulnerability - where separating users in space can enhance safety for all road users.Applications
FHWA’s Bikeway Selection Guide and Incorporating On-Road Bicycle Networks into Resurfacing Projects assist agencies in determining which facilities provide the most benefit in various contexts. Bicycle lanes can be included on new roadways or created on existing roads by reallocating space in the right-of-way.In addition to the paint stripe used for a typical bicycle lane, a lateral offset with painted buffer can help to further separate bicyclists from vehicle traffic. State and local agencies may also consider physical separation of the bicycle lane from motorized traffic lanes through the use of vertical elements like posts, curbs, or vegetation. Based on international experience and implementation in the United States, there is potential for further safety benefits associated with separated bicycle lanes. FHWA is conducting research on separated bicycle lanes, which includes the development of crash modification factors, to be completed in 2022 to address significant interest on this topic.
Considerations
The following are considerations to adding a bicycle lane by reducing lane and shoulder widths:• City and State policies may require minimum bicycle lane widths, although these can differ by agency and functional classification of the road.
• Bicycle lane design should vary according to roadway characteristics (e.g., motor vehicle volumes and speed) in order to maximize the facility’s suitability for riders of all ages and abilities and should consider the travel needs of low-income populations likely to use bicycles. The Bikeway Selection Guide is a useful resource.
• While some in the public may oppose travel lane narrowing if they believe it will slow traffic or increase congestion, studies have found that roadways did not experience an increase in injuries or congestion when travel lane widths were decreased to add a bicycle lane.
• Studies and experience in US cities show that bicycle lanes increase ridership and may help jurisdictions better manage roadway capacity without increased risk.
• In rural areas, rumble strips can negatively impact bicyclists’ ability to ride if not properly installed. Agencies should consider the dimensions, placement, and offset of rumble strips when adding a bicycle lane.
• Strategies, practices, and processes can be used by agencies to enhance their ability to address equity in bicycle planning and design.
Longitudinal Rumble Strips and Stripes on Two-Lane Roads
Longitudinal rumble strips are milled or raised elements on the pavement intended to alert drivers through vibration and sound that their vehicle has left the travel lane. They can be installed on the shoulder, edge line, or at or near the center line of an undivided roadway.Rumble strips are edge line or center line rumble strips where the pavement marking is placed over the rumble strip. This can increase the visibility and durability of the pavement marking during wet, nighttime conditions, and can improve the durability of the marking on roads with snowplowing operations.
With roadway departure crashes accounting for more than half of the fatal roadway crashes annually in the United States, rumble strips and stripes are designed to address these crashes by alerting distracted, drowsy, or otherwise inattentive drivers who drift from their lane. They are most effective when deployed systemically.
Transportation agencies should consider milled center line rumble strips (including in passing zone areas) and milled edge line or shoulder rumble strips with bicycle gaps for systemic safety projects, location-specific corridor safety improvements, as well as reconstruction or resurfacing projects.
Considerations
• Rumble strips are relatively low-cost, and economic analyses have indicated benefit/cost ratios that exceed 100.
• Where rumble strips cannot be placed due to noise concerns, agencies may consider a design using an oscillating sine wave pattern (also known as “mumble strips”) that reduces noise outside of the vehicle. However, the safety benefits of this design need more study.
Maintenance concerns:
• Where rumble strips are placed along a pavement joint, there are typically no issues with joint stability if the pavement structure and joint was already in good condition.
• Studies have shown no evidence of issues related to snow, ice, or rain build-up in the rumble strip.
Redundancy Is Critical
The Safe System Approach emphasizes that redundancy is critical, and safer roadways mean incorporating design elements that offer layers of protection to prevent crashes from occurring and mitigate harm when they do occur. Through the NRSS, the Department will focus on advancing infrastructure design and interventions that will significantly enhance roadway safety.
Key Departmental Actions to Enable Safer Roads
Safer Vehicles
Expand the availability of vehicle systems and features that help to prevent crashes and minimize the impact of crashes on both occupants and non-occupants.
The role of vehicle safety performance in avoiding or mitigating the harm of crashes cannot be overstated. Seat belts and air bags, for example, prevented an estimated 425,000 fatalities in traffic crashes since they were first required through regulatory requirements called the Federal Motor Vehicle Safety Standards (FMVSS).
The next generation of motor vehicles will increasingly have the technology necessary to prevent certain crashes from occurring in the first place and to mitigate harm to those outside of the vehicle when a crash happens. This is particularly important as the proportion of roadway fatalities involving people outside of a vehicle has increased over the past few years.
Deploying Advanced Vehicle Safety Technologies
The deployment of technologies to improve vehicle safety has rapidly accelerated in the last five years. Data from the New Car Assessment Program shows substantial increases over time in the percentage of passenger motor vehicles equipped with advanced driver assistance system technologies.
FCW: Forward Collision Warning
LDW: Lane Departure Warning
CIB: Crash Imminent Braking
DBS: Dynamic Brake Support
PAEB: Pedestrian Automatic Emergency Braking