Intersections are critical for AAA bikeways. Many vehicle-bike conflicts occur at intersections, and a high-stress intersection experience for people bicycling along a roadway can negate the effects of even the best segment design.
In their intersection guide, Don’t Give Up at the Intersection
, NACTO authors emphasize the importance of reducing turning speeds, increasing the visibility of people bicycling, and giving priority at intersections to people bicycling. A variety of tools are available to support these strategies, including protected and dedicated intersections, and minor street crossings.
The MassDOT guide provides additional detail on intersection and signal design, while the FHWA summarizes considerations at driveways. For bicycle boulevard crossings of arterials, refer to the NACTO Urban Bikeway Design Guide
section on bicycle boulevard design.
Protected intersection design supports the continuation of AAA facilities through intersections, especially at the intersection of multiple streets in a local bikeway network. Protected intersections use corner islands, curb extensions, and color paint to delineate bicycle and pedestrian movements across an intersection. Slower driving speeds and shorter crossing distances increase multi-modal safety, while separated bike lane crossings allow people biking to make left turns and transition to intersecting AAA bikeways without merging across lanes of through-moving traffic.
Where space is limited and intersection geometry may preclude a full protected intersection, a dedicated intersection combined with dedicated signal phasing can also effectively reduce conflicts and improve bicyclist comfort at intersections.
For further detail on protected and dedicated intersection design, refer to Chapter 4 of the MassDOT Guide.
Protected Intersection Diagram
Signal design along separated bike lane corridors is critical to the safe and successful implementation, especially at intersections with high conflicting turn movements. In these contexts, dedicated phasing for turning vehicles and people bicycling reduces conflicts by separating users in time. Where fully separate phasing for bicycles is not warranted, a leading bicycle/pedestrian interval can improve bicyclist visibility for turning vehicles.
Chapter 6 of the MassDOT Separated Bike Lane Planning and Design Guide
provides detailed considerations for phasing scheme options, signal equipment, and signal timing. The chapter provides thresholds for conflicting vehicle volumes that require consideration of dedicated phasing. NACTO’s Don’t Give Up at the Intersection
provides additional resources and considerations for signal design. Key considerations for signal design include:
- Existing signal equipment and visibility
- Conflicting vehicle turn volumes
- Signal timing, phasing, and intersection clearance
- Sight lines
- Actuation and detection
The FHWA Separated Bike Lane Planning and Design Guide
provides sight distance guidelines for driveways and small intersections. In general, 20 feet of clear space (parking restriction) on both sides of a driveway are required to ensure clear field of view for drivers entering and exiting driveways to see people and yield to people bicycling. In some cities, less daylighting is used at single-family driveways. This is generally implemented on a case-by-case basis.
Chapter 5, Step 3 provides detailed midblock considerations, including specific recommendations and considerations for driveways on one-way or two-way streets and with one-way or two-way separated bike lanes.
Residential roads with low traffic volumes and speeds (<2000 ADT /<20 MPH), and designed as bicycle boulevards, can feel safe and comfortable for users of AAA as part of the Countywide Bikeways Network. Along many bicycle boulevards, arterial crossings—especially at uncontrolled locations—pose a significant barrier to access, safety, and comfort along the bike routes. These uncontrolled bikeway crossings typically correspond with crosswalks where pedestrians are the most vulnerable user, the FHWA STEP Guide for Improving Pedestrian Safety at Uncontrolled Crossing Locations
provides the best guidance for selecting crossing enhancements appropriate for each context.
When selecting the appropriate crossing treatments, designers should consider bicycle use and access. For example, median refuges need breaks along the bikeway alignment and bicycle actuation is needed for pedestrian hybrid beacons or pedestrian signals.