Sunday, April 22, 2012

Left-Side Bike Lane on Commonwealth Avenue, Back Bay, Including Underpass, but not Including Transition from Right to Left

By, Isaac Almy


Commonwealth Avenue is two way street in Boston with each direction separated with a vertical park in the middle. 

Commonwealth Avenue Highlighted in Blue
In 2010 a bike lane was added to the left side of the street. Before the bike lane was added cyclists rode on the right side of the street next to parked cars. This put the cyclist at risk of getting "doored" as a person got out of their vehicle.

Commonwealth Avenue Before Added Bike Lanes (google street view)

Added Bike Lanes

Bike lanes were added in each direction on the left side. At the start of the bike lanes markings are made to tell the cyclist to ride on the left.

Start of Left Side Bike Lanes
You can see from the picture that sometimes cars will be parked where the markings are. 

Left Side Bike Lane on Commonwealth Avenue
The bike lane is to the left of the cars and to the right of the park. In heavy traffic it is easy for a bike to travel faster than a car. The bike lane isn't next to any parked cars and so there is no risk of dooring. The bike lanes are about 4ft wide. There is enough space for one cyclist but not for bikes going side by side. Cyclists can safely travel in the lane uninterrupted by cars. 

Boston Cab Driver Blocking the Bike Lane
Unless a Boston cab driver blocks the lane. Most cars will stay in their lane and keep the bike lane clear.

Bike Box

 On cross streets where a bike can make a right turn. A bike box is added at the intersection. You can also see there are green markings leading up to the intersection. This makes more aware of cyclists.

Cars Stopping Before the Bike Box

At the intersection cars will stop before the bike box, which allows bikes to safely cross the street in front of them. 

Boston Cab Driver in the Bike Box
Unless a Boston cab driver gets in your way.


At the intersection of Massachusetts avenue and Commonwealth Avenue an underpass was built to allow Commonwealth to go underneath Massachusetts Avenue. The bike lane stays on the left side and a buffer zone is created between the cars and the bikes. Cars going under the underpass are going 30mph or more and the buffer zone protects the cyclists from the higher speed vehicles. 

Bike Lane Before the Underpass with a Buffer Zone
The buffer area is about 2ft in width. The cars are a safe distance away from the cyclist. Going underneath the underpass is a breeze and merging back into traffic is simple because the bike lane continues on the other side.


The bike lanes on commonwealth avenue are a great addition to Boston's bicycle network. The bike lane on the left side of the street prevents dooring. The buffered bike lanes for the underpass add some space for the cyclist and has little effect on cars. When cars are making a left turn off of Commonwealth they need to pay attention to cyclists going through the intersection. Motorists aren't used to looking for cyclists as they turn left. The cyclist needs to be aware of any turning cars and make adjustments in speed as needed.

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