CHAPTER 2

Safety Principles and Bikeway Selection

2.1 Safety Principles and Strategies

FHWA has embraced the Safe System approach as a strategy to eliminate serious injuries and deaths resulting from crashes on the transportation system. As noted on FHWA’s website, “This approach requires a supporting safety culture that places safety first and foremost in road system investment decisions [FHWA n.d. (c)]. This system is based on the following principles [FHWA n.d. (a)]:

• Death and serious injuries are unacceptable,
• Humans make mistakes,
• Humans are vulnerable,
• Responsibility is shared,
• Safety is proactive, and
• Redundancy is crucial.

The FHWA Bikeway Selection Guide applies the Safe System approach as a foundational philosophy to guide bikeway selection. It identifies seven bikeway network design principles for developing effective bicycle networks that improve bicyclist safety (see Figure 2). These benefits can flow to other users who operate on bikeways (e.g., micromobility users).

Bicycle networks and bikeways need to be designed with the goal of reducing injuries and fatalities. When planning bikeway networks and designing bikeway facilities, practitioners can improve safety by applying Safe System principles through the following strategies:

• Selecting an appropriate bikeway. Physically separate bicyclists from motor vehicle traffic where motor vehicle volumes are higher and/or the speed differential between bicyclists and motor vehicles is large.
• Providing space. Avoid overly constrained conditions that do not allow users space to react to mistakes and reduce bicyclists’ comfort and safety.
• Minimizing exposure to conflicts. Minimize and consolidate areas where bicyclists are exposed to motor vehicle traffic to the maximum extent practicable.
• Managing motorist speed. Where conflict points between bicyclists and motorists cannot be further minimized, manage motorist speed to reduce the likelihood of serious or fatal injury.
• Ensuring awareness. Ensure awareness of bicyclists is maximized at conflict points and the right-of-way between users is clear.

Additionally, to serve the broadest range of users, the provision of an effective bikeway network is as important as providing a bikeway on an individual street. Effective bikeway networks are comfortable, safe, connected, and direct, as well as relatively dense (cohesive), connecting desired destinations (attractiveness) while minimizing delays or gaps (unbroken flow) (Schultheiss et al. 2019).

2.2 Bikeway Selection

As discussed in NCHRP Web-Only Document 414: Safety Evaluation of On-Street Bicycle Facility Design Features, all bikeways have been found to be effective at improving safety outcomes compared to baseline shared lane conditions in large part because they create separate operating space for bicyclists. A description of the research on which this guide is based is available on the National Academies Press website (nap.nationalacademies.org) by searching for NCHRP Web-Only Document 414: Safety Evaluation of On-Street Bicycle Facility Design Features.

The selection of an appropriate bikeway based on conflict potential and likely impacts of conflicts is fundamental in the Safe System approach. Bicyclists are inherently vulnerable and at disproportionate risk if they are hit by a motor vehicle due to the large difference in kinetic energy between a person and a motor vehicle in the event of a crash, even when crashes occur at lower operating speeds. Within a Safe System framework, it is important to separate users in space, and sometimes in time (at traffic signals), when conflicts are likely to occur. As noted in the FHWA Bikeway Selection Guide (see Figure 3), bikeways have different performance characteristics to manage conflicts resulting from human mistakes.

Bicycling as an activity is open to people of all ages and abilities who are interested in and able to ride a bicycle. The design of bicycles is rapidly changing to accommodate a wide range of users. The expansion of bikeway networks combined with the increasing electrification of bicycles is expanding the demand for bicycling. The electrification and increasing availability and use of micromobility transportation devices are also increasing the demand for bikeways while increasing the mixture of users operating within them. Bikeways are attractive facilities for people using micromobility and personal mobility devices; in some communities, these users are required to operate on bikeways. Like bicyclists, these users are also disproportionately vulnerable in a crash with a motorist, and many of these users are uncomfortable operating on

roadways in shared lanes with motor vehicle traffic, especially in areas with higher motor vehicle volumes and operating speeds. Research consistently shows the volume, operating speed, and the relative mixture of motor vehicles (e.g., trucks, buses, cars) operating on a roadway are the primary factors impacting the comfort and safety of bicyclists. While crashes with micromobility users was not documented in this research, for purposes of this guidance, these users are assumed to be present and operating on bikeways.

Bikeway selection guidance in North America has been evolving over the past decade to reflect lessons learned from abroad, lessons learned from implemented bike networks in North America where bicycle ridership is higher relative to peer cities, and research that shows which types of bicycle facilities both attract users and provide safe outcomes. Injury and fatality risks sharply rise for vulnerable users when they are involved in a crash with motor vehicles operating at speeds over 20 to 25 mph. Exposure to potential conflicts also increases as motor vehicle traffic volumes increase above 6,000 vehicles/day on a street as it becomes increasingly difficult for motorists and bicyclists to share operating space.

In recognition of vulnerable user crash risk and the need to consider vulnerable user comfort when operating with or adjacent to motorists, NACTO, AASHTO, FHWA, and international design guidance typically recommend separated bicycle lanes be considered when motor vehicle volumes exceed 6,000 vehicles per day and speeds exceed 25 mph. The FHWA Bikeway Selection Guide (Schultheiss et al. 2019; see Figure 4) and the NACTO Designing for All Ages and Abilities Guide (NACTO 2017; see Figure 5) are representative of the thresholds found in these documents.

2.3 Chapter Summary

The FHWA Bikeway Selection Guide applies the Safe System approach as a foundational philosophy to guide bikeway selection. It identifies seven bikeway network design principles for developing effective bicycle networks that improve bicyclist safety: safety, comfort, directness, connectivity, cohesion, attractiveness, and unbroken flow. It is important to separate users in space, and sometimes in time (at traffic signals), when conflicts are likely to occur. Bikeways at midblocks are expected to reduce the fatalities and injuries resulting from crashes and conflicts between bicyclists and motorists as well as other active users such as pedestrians and micromobility devices. The research shows that volume, operating speed, and the relative mixture of motor vehicles (e.g., trucks, buses, cars) operating on a roadway are the primary factors impacting the comfort and safety of bicyclists. Therefore, the selection of bikeway type will depend on these factors. The FHWA Bikeway Selection Guide indicates that injury and fatality risks sharply rise for vulnerable users when they are involved in a crash with motor vehicles operating at speeds over 20 to 25 mph. Exposure to potential conflicts also increases as motor vehicle traffic volumes increase above 6,000 vehicles/day [average daily traffic (ADT)] on a street as it becomes increasingly difficult for motorists and bicyclists to share operating space. Based on this assessment, the FHWA Bikeway Selection Guide recommends implementing separated bicycle lanes when traffic conditions exceed these thresholds (i.e., posted speed limit over 25 mph and traffic volume of over 6,000 vehicles/day) to provide a safe and comfortable bicycling space to all ages and abilities. Contextual and design considerations to improve the safety of bicyclists at separated bicycle lanes are discussed in Chapters 3 and 4, respectively.