Better bike lanes: Design elements
These elements create more comfort for people biking along streets and through intersections. We incorporate these elements in our designs where they are appropriate. For more information on our bike lane efforts, please visit our Better Bike Lanes website.
Buffers increase space between people biking and people driving. They help prevent unintentional collisions that could cause serious harm to the people involved.
Buffers are part of the design for separated bike lanes and buffered bike lanes. They provide space between people biking and people getting into or out of a vehicle. Buffers may be located on either side of the parking lane.
When the buffer is on the passenger side of the vehicle, it is always at least three-feet wide. The buffer may be wider near accessible parking spaces, and when behind bus stops. These buffers may be painted on the street, or may be constructed islands.
Reducing the risk of "dooring"
Buffers offer more space for people to open their car doors without unexpectedly hitting a person biking, which is also called “dooring”. "Dooring" is one of the most common types of crashes involving people biking.
Offset intersections create more space between car travel lanes and the parallel bike crossing. This extra space helps drivers see people biking before completing a turn. It also encourages drivers to turn at slower speeds.
When a driver is making a right turn, it can be hard for them to see a person biking on the right side of their car. This photo shows the driver's view at an intersection with a standard bike lane. There is a person biking on the right side of the car. But, they are not visible in the mirror at all. Only a small part of the bike tire is visible in the bottom right corner of the window.
At an offset intersection, turning drivers can more easily see people bicycling or walking. This photo shows an intersection with a separated bike lane and offset intersection. The extra space between the car travel lanes and the bike lane allows drivers to:
- begin their turn without fully blocking vehicles behind them
- see people bicycling or walking, and
- yield to people bicycling or walking.
People driving don't need to fully turn their head or rely on their mirrors when making a right turn at offset intersections. This photo shows the turning driver's view at an offset intersection with a separated bike lane. A person biking is clearly visible to the driver.
Offset intersections also reduce the area in which crashes can occur to a single point where turning vehicles cross the bike lane. By slowing down turning vehicles, this design can reduce the severity of turning-related crashes.
In many cases, people on bikes can use the general traffic signals. But, in some cases, we provide bike-only signals.
Bike signals are useful when our streets have:
- high volumes of turning vehicular traffic
- high volumes of bicyclists
- a two-way separated bike lane, or
- skewed or multi-leg intersections that are unique.
At intersections with bike signals, cyclists should not follow general traffic and pedestrian signals. The bike signals show the safest time for bike riders to go through an intersection.
We have two types of bike signals in the City of Boston:
- Some are standard signals with a sign showing that it is a bike signal.
- Others also have the sign, but the signal itself has a bike symbol.
Intersection conflict markings
On streets with bike lanes, we add green stripes where there is the potential for conflicts between drivers and bicyclists. They alert turning drivers to look for people on bikes.
We use this treatment most commonly at intersections and driveways. In some places, we use green stripes to help show people riding bikes where they should be positioned in the street. This is especially important when they are crossing Green Line trolley tracks.
At some intersections with signals, we set aside a space between the crosswalk and the traffic lane for people on bikes. This bike box provides a safe and visible spot for people on bikes to wait for the light to change.
Two-stage turn boxes
Merging across lanes on a busy street to make a turn can be tough or scary for people riding bikes. Where possible, we provide a two-stage turn box. The box helps make that turn safer and less stressful.
Bicyclists first ride through the intersection to the two-stage turn box. Then, they turn their bikes to head in the correct direction. When the light turns green, bicyclists continue straight.
Two-stage turns are often necessary on separated bike lanes. Exiting the bike lane mid-block is generally not allowed by design.