The most appropriate cross-section for a bikeway will be contextual.
Designers need to prioritize the overall safety of people using the bikeway and pedestrians first. This includes a review of intersection operations and the potential to mitigate conflicts. Other factors can then be considered, including available right-of-way, connectivity to the bike network, adjacent land uses and destinations, transit stops, and maintenance needs.
Unidirectional or Bidirectional Bikeways
Unidirectional bike lanes are the preferred design in most situations and should be considered before bidirectional bike lanes. They are more intuitive for everyone using the street, including people biking, walking, and driving. Unidirectional bike lanes typically:
- Provide clear and direct connections with the overall transportation network;
- Require fewer modifications to signal operations at intersections;
- Present fewer conflicts at driveways and unsignalized intersections;
- Transition more easily to other bikeways; and
- Limit the potential for conflict between people riding in opposite directions.
Bidirectional bike lanes can be helpful in some situations. Where there are significantly fewer intersections and driveways on one side of the street, a bidirectional bike lane may be safer and more comfortable. They can provide an important contraflow connection on a one-way street with motor vehicle volumes and speeds that preclude a bike boulevard or advisory bike lanes. They may also be applied in highly constrained rights-of-way where minimums for all other street elements are already achieved, including the total number and width of general travel lanes.
Designers using a bidirectional bike lane must design all intersections and driveways more carefully, including adding bike signals, increasing the clear distances in both directions, and slowing turning speeds.1 Transitions at the beginning and end of the bidirectional bike lane must also be designed thoughtfully, enabling clear and safe connections to other bikeways and alignments.
Alignment
Bikeways should be provided in both directions of two-way streets wherever possible. If available right-of-way, motor vehicle speeds, or overall traffic volumes allow, consider a bike boulevard or advisory bike lane design. Where necessary, the asymmetrical application of constrained bike lanes or protected bike lanes may still be appropriate, as these designs will improve safety for everyone on the street.
Bikeways should be provided on both streets of one-way couplets.
Accommodating bidirectional biking on a street that previously only served one-way operation can greatly expand the reach of the bike network. Bike boulevards should allow for people on bikes to travel in both directions, regardless of whether the street allows one- or two-way motor vehicle operations. Contraflow bike lanes, either as constrained or protected bike lanes, may be added to provide two-way bike travel on a one-way street.
Right- or Left-Aligned Bike Lanes
Protected and constrained bike lanes should be designed on the right-hand side of the roadway, operating in the direction of the adjacent motor vehicle traffic, wherever possible.
At intersections and driveways, designers must provide adequate sight distance, bike lane protection, and turn-calming treatments. Additional temporal separation to reduce conflicts should be considered at intersections with higher volumes of turning motor vehicles. Left-aligned bikeways are atypical; designers will need to make them more conspicuous and visible to drivers through treatments such as protected bike phases at signalized intersections, advanced stop lines, and increased daylighting ahead of intersections. (See Design Strategies for Signalized Intersections.)
One-way streets with frequent transit service may be good candidates for left-aligned bikeways, particularly if the right-of-way is not available for boarding islands. (See Transit Stops.)
On one-way streets, contraflow bike lanes should be located on the left side of the street.
Center-Running Bike Lanes
Avoid center-running bike lanes. When used as short connections at dogleg or staggered intersections, they can be helpful in transitioning from one bikeway to another. However, they pose significant challenges for intersection design, including a higher crash risk if conflicts are not well-separated. In the North American context, center-running bike lanes require signalized intersections with bike signals; unsignalized intersections are not recommended. Restrictions on turning movements and from cross-street traffic are often necessary.
- Research indicates that bidirectional bike lanes may experience higher crashes at unsignalized intersections than unidirectional bike lanes.
Schepers, J.P., P.A. Kroeze, W. Sweers, and J.C. Wüst. SRoad factors and bicyclemotor vehicle crashes at unsignalized priority intersections.m Accident Analysis & Prevention 43, no. 3 (May 2011): 853-861. https://doi.org/10.1016/j.aap.2010.11.005. ↩︎