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"Bike box" at
Garden Street and Concord Avenue intersection, Cambridge, Massachusetts

Let's examine the intersection of Garden Street and Concord Avenue in Cambridge, Massachusetts, an intersection with an unusual treatment, a "bike box". This is a space for bicyclists to stop ahead of motor vehicles waiting for a traffic light.

General issues about "bike boxes" are discussed on another Web page on this site. Now, we'll look at how the Concord Avenue/Garden street intersection complies with theoretical and practical requirements.

Garden Street runs from the foreground to the background in the photo below. The "bike box" was installed here in an attempt to solve a real problem: students headed from the Radcliffe campus to the Harvard campus -- from the foreground toward the left rear in the photo -- would ride several blocks on the left sidewalk before turning left at the location of the green arrow. Riding on the left sidewalk exposes bicyclists to a very elevated risk of collisions with motorists exiting cross streets.


advstop1.jpg (37382 bytes)

John S. Allen photo


For motorists, the intersection is a "Y" intersection, but the "Y" is upside down as viewed in the photo. The car waiting in the background (under the suspended traffic signals, with headlights on) would bear left (that is, toward the right of the picture) to turn from Garden Street onto Concord Avenue.

For bicyclists, the intersection is a diagonal, "X" intersection. Bicyclists using the bike box in the foreground may turn left into a curb cut at the location indicated by the green arrow in the photo, in order to travel across a raised pedestrian plaza and then continue on another street.

How well does this installation meet theoretical requirements for safety discussed in the other page on bike boxes?

  • Garden street is only a two-lane street. So far, so good.

  • The intersection does have traffic signals. So far, so good.

  • There is no right-turning traffic here, so there are no right turns on red which would conflict with the use of the "bike box". So far, so good.

  • However, this installation lacks an advanced red or other warning for the bicyclists, and so bicyclists have no way to know when it is safe to swerve in front of vehicles waiting for the traffic light.

On the last count, the installation fails the safety test. A bicyclist can not know when the light is going to turn green and vehicles may start moving.

There are some additional, specific problems with this installation:

  • The markings and signage are not very clear. As of 2002, this is the only "bike box" in the Boston, Massachusetts area, worsening the problem of unfamiliarity. Clearly, the motorist in the left foreground of the photo did not understand the "bike box".

  • The intended travel path of bicyclists -- into a curb cut rather than a street -- is unusual and not at all obvious.

  • Cara Seiderman, Bicycle coorinator for the City of Cambridge, explains that both Garden Street westbound and Concord Avenue eastbound have a red indication when the bicyclists would be turning left on green. However, in this three-way intersection, it is not obvious when the conflicting  traffic is stopped by traffic lights which bicyclists can not see. The situation demands a separate left turn signal. There is none here.

  • Bicyclists do not turn sharply left to enter the curb cut, but rather, must proceed diagonally across the intersection, toward the oncoming traffic. Without assurance that the oncoming traffic will continue to be stopped by the traffic signal, this movement does not appear safe to the bicyclists.

  • Though the pedestrian signals are controlled by pushbutton actuators, the potential exists for conflict between bicyclists entering the crosswalk and pedestrians waiting to cross.

The installation discourages  normal vehicular left turns, or normal pedestrian-style left turns (particularly as there is no crosswalk across the intersection in the bicyclists' initial direction of travel), while encouraging bicyclists to overtake motor vehicles on the right and swerve out in front of them. There are additional problems with the unusual destination of the left turn at a curb cut, and the unclear markings and signage. Only a small percentage of bicyclists uses the "bike box", probably, in part, because many still wrongly consider it preferable to ride on the left sidewalk and in part because many do not understand what the "bike box" is. There are also legal issues (see below), which confuse the status of bicyclists using a "bike box" in Massachusetts.

What should be done here?

My preferred treatment, assuming that left turns are to be encouraged here at all,  would be a left turn bike lane for bicyclists to the left of the main travel lane, with a distinct, dashed marking of the bicyclists' track across the intersection. This treatment would encourage bicyclists to merge before reaching the intersection, and would delineate the left turn movement. A left turn arrow phase in the traffic signal would clarify when bicyclists can safely turn left.

If there is to be a "bike box" at this location, it needs an additional warning signal to avoid bicyclists' swerving out just before the traffic signal turns green. Two signals which turn red at different times could, however, lead to confusion.

It would be better if the destination of the left turn were at street level rather than up a curb cut. The left turn continues to a section of Concord Avenue which has been disconnected by the brick-paved pedestrian plaza. The lack of a channel for bicyclists other than the curb cut at the crosswalk contributes to confusion about whether a left turn can be made on a protected signal phase, and then to potential conflicts between pedestrians and bicyclists.

Massachusetts traffic law and the "bike box"

Our examination requires a look at some provisions of Massachusetts traffic law. This is the most unusual in the USA, never having been conformed to any version of the Uniform Vehicle Code. The Web links in the following paragraphs are to the complete sections of Massachusetts statutes, and to a Web page with parallel provisions from the Uniform Vehicle Code.

Massachusetts law does not include the provision of the Uniform Vehicle Code allowing jurisdictions to establish special rules for bicyclists to make left turns. Massachusetts law does have a provision allowing special rules for all vehicles. Whether different rules may be established for specific categories of vehicles is not spelled out:

Ch. 90 14.

...The [jurisdiction] may provide for the placing of traffic control devices in accordance with department standards to indicate the course to be traveled by vehicles turning at such intersections. Such course may be other than as is prescribed by the requirements for lane usage set forth in this section.

Most states allow overtaking on the right with caution, with few additional restrictions. Massachusetts law prohibits drivers -- including bicyclists -- from overtaking on the right under the conditions which usually apply with the bike box:

Ch. 89 2. Passing vehicle traveling in same direction

...The driver of a vehicle may, if the roadway is free from obstruction and of sufficient width for two or more lines of moving vehicles, overtake and pass upon the right of another vehicle when the vehicle overtaken is (a) making of about to make a left turn, (b) upon a one-way street, or (c) upon any roadway on which traffic is restricted to one direction of movement.

There are no left turns by motor vehicles here, and thsi is a two-way street.

On the other hand, Massachusetts law specifically permits bicyclists to overtake moving motor vehicles on the right, and without any restriction:

Ch. 85 11B. Bicycles, operation and equipment...

...the bicycle operator may keep to the right when passing a motor vehicle which is moving in the travel lane of the roadway...

As they approach the "bike box", bicyclists are generally overtaking stationary vehicles on the right, but the definition of moving is somewhat unclear; it may include motor vehicles which are waiting in traffic, even if not moving at the moment. The law does not spell out that it is legal to overtake non-motorized vehicles on the right, and so it may not be legal to overtake another bicyclist on the right when that bicyclist is waiting in the "bike box" unless it can be ascertained that the bicyclist is waiting to turn left. When would a bicyclist want to overtake another bicyclist who is in the "bike box" and not turning left? As an example, the traffic light may have just changed and a bicyclist in the "bike box" not yet restarted. It is in any case often not possible to know whether the bicyclist in the "bike box" is preparing to turn left or not.

Such unclear definitions and failure to address typical situations are common in Massachusetts traffic law.

The Massachusetts law includes wording about lane use similar but not identical to that in the Uniform Vehicle Code:

Ch. 89 4A. Driving vehicles in a single lane; motorcycles, riding and passing

...the [driver of a vehicle] ... shall not move from the lane in which he is driving until he has first ascertained if such movement can be made with safety...

This Massachusetts law is defective in that it uses the words "lane of traffic" instead of "line of traffic", as in the Uniform Vehicle Code, and so does not account for lateral  movements within a lane by narrow vehicles such as bicycles and motorcycles. So, Massachusetts law does not specifically prevent a bicyclist or motorcyclist from merging across a lane, even when this cannot be done in safety. But also note,

Ch. 90 14.

...When approaching for a left turn on a two-way street, an operator shall do so in the lane of traffic to the right of and nearest to the center line of the roadway...

Given the lack of a special left turn provision for bicycles, and assuming that the definition of "operator" includes bicyclists, this law prohibits bicyclists from approaching the "bike box" in a right-side bike lane to make a left turn. However, Ch. 90 14 generally makes prescriptions for motor vehicle operators and may possibly not apply to bicyclists. As an aside, this law is clearly faulty in that it does not account for streets that have multiple left turn lanes.

Unless Ch. 90 14 can apply differently to different categories of vehicles, it can be argued that Massachusetts law often prohibits the use of the "bike box" as intended.

There is no bike lane before the bike box here, and so, under Massachusetts law, bicyclists may approach the "bike box" anywhere in the right travel lane (good enough), and probably may cross to the left side of the travel lane without ascertaining whether they can do so in safety (not good).  They may or may not overtake stopped motor vehicles on the right here (not good), depending on what is defined as a "moving motor vehicle". Hey, I didn't write these laws!


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