Bicycle Safety Guide and Countermeasure Selection System
Example of a stop-controlled path approach. http://www.pedbikeimages.org/ - Danny McCullough
Where paths must cross roadways, driveways, or other paths, it is important that the path design facilitates the safest and most convenient crossing movements possible. Where there is a conflict between safety and convenience, safety should take precedence. Path intersections with roadways offer special design challenges, especially since path users may have a wide range of cycling skills and diverse characteristics. The AASHTO Guide for the Development of Bicycle Facilities provides design guidelines for midblock, adjacent path, and complex intersection path crossings where the path crosses a roadway at an existing intersection or driveway. Signs and signals for the roadway and path, end of path transitions, markings, sight and stopping distance, ramp widths, and other intersection design issues are discussed, but each situation requires judgment on the part of the designer.
Both path-to-path and path-to-roadway intersections require careful planning and construction to maximize safety. Where crossings must occur, priority right-of-way should be established based on the type of intersecting travel-way, traffic volumes, speed, and other factors. Path users should be counted in the volumes, and where paths cross low-volume roadways or driveways and path use is high, priority should be given to the path. Warning and regulatory signs, traffic signals, and pavement treatments or markings should be used to clearly delineate which corridor has the right-of-way, coordinate interactions, and guide path users to safe crossing locations. A traffic control device (sign or signal) should be installed at all path-roadway intersections. Efforts should be made to minimize crossing delays to path users as some may be unwilling to tolerate significant delays.
There are many considerations at locations where paths must cross roadways at-grade. The path should intersect the roadway at as close as 90 degrees as possible to reduce crossing distance and improve sight lines. If the path crosses a busy, multilane, or high-speed road, a refuge island is a treatment that enables path users to cross one leg of the roadway at a time. Lighting can also enhance the safety of path intersections with roadways, railways, and other paths, especially if extensive nighttime use is expected (such as in a busy urban area or near a college or university campus).
One particular challenge where two-way paths intersect with streets and driveways is that motorists are often not expecting bicyclists from both directions and may not look for them. Signing and marking can be used to assist with motorist expectations, but careful design and clear sight lines are critical. Roadway treatments such as warning signs and pavement markings also let road users know they are approaching an area where bicyclists, pedestrians, and other path users may be crossing or present. Vegetation and other obstructions should be kept clear near intersections for adequate sight distance. Related to the challenge of two-way paths at intersections is that at the location where two-way paths end, bicyclists may ride on the wrong side of the street to enter or leave the path, leading to an increased crash risk.
Since a big attraction for many users of the shared-use path is its separation from motor vehicle traffic, grade separation through bridges and tunnels should be considered at crossings. For new construction, the cost of off-grade crossings may be considered prohibitive but may be the best alternative where a path needs to cross a busy or high-speed corridor or if path use is expected to be high. Some communities such as Boulder, CO (see case study), have used off-grade crossings extensively for bike and pedestrian corridors. For safe and effective overpasses and underpasses, adequate lighting is important for travel and for personal safety (see tunnels/underpasses).
Pathways must link to the street network and access points should be clearly marked and signed. Curb cuts should be flared to allow bicyclists to make safe turns onto or to exit the path. On unpaved paths, a paved apron should extend at least 10 ft from the edge of paved roadways. To prevent motorized traffic from inadvertently or intentionally accessing the path, signs clearly noting that motorized traffic is prohibited, as well as brightly painted bollards or medians, should be installed in the center of a 10 ft wide or less path, or no less than 5 ft apart on a wider path. Since bollards may present a hazard to path users, alternatives to the bollards, such as a small landscaped median or split path, should be strongly considered. If bollards are used, they should be brightly painted and set back from the intersection such that users can focus on safe crossings. In all cases access for maintenance and emergency vehicles must be provided.
Intersections and driveways present many hazards to users of shared-use paths and safe crossings must be provided.
Intersection costs are part of the overall cost of the path. Some treatments may be incorporated into roadway or intersection upgrades.
Authors and Acknowledgements