Why four lanes don’t fit

Arlington Town Hall on Tuesday night. Not quite to capacity, but very full.

April 2011 hearing, nearly a full house

I’ve been mining the transcript of the 25% design hearing that MassDOT held at Town Hall in April 2011, looking for things we ought to remember as we head into yet another such hearing this February 26.

One exchange addresses the question of, in effect, why can’t we have four lanes? Here Richard Azzalina, the Town’s lead consulting engineer, begins with a very provocative statement (Transcript 72.3–75.11):

First of all, I just want to be clear, Mass. Ave. is not designated or is not striped as a four-lane facility. Okay? It’s a very wide one lane.

Azzalina is not denying that people drive down Mass. Ave. 2 abreast. His point is more subtle, that they do so by frequently weaving back and forth across “lanes” that, if marked, would not be tenable:

And the reason why I say that, okay, is because if you were to go out there and stripe it as a four-lane facility today, you would not have enough width in the right travel lane to accommodate a shared-use bicycle facility, and that facility would not have the same benefits that a designated bicycle lane has in a three-lane facility in terms of worrying about somebody opening a car door. You don’t have the additional [width]….

This plan is a safer plan. People will drive it more orderly. What’s out there today is a very wide open space. People drive all over the place. And that’s what’s very dangerous about the corridor….

Here he makes the obvious point that that the weaving is “dangerous.” But he goes on to explain why it happens, and why a striped four-lane design would be worse:

I can show you a graphic later on if you’d like showing what would happen if you tried to squeeze two vehicles in the 25 feet of pavement plus the parking stop. Okay? If there’s a bus—if there’s a bus—and there are plenty of buses that drive that corridor…. That bus encroaches into the left lane to pass someone who is on a bicycle.

Detail from FDR (p. 34) showing insufficient space in 14′ shared lane (at right).

And the reason he does that is because there’s not sufficient space between the bus [and parked cars] to stay in his lane and have the bicycle, you know, stay where they’re supposed to stay…. You would have to narrow the sidewalks from what they have today.

Azzalina is just recapping his work in the Functional Design Report that, along with the plan drawings, comprise the 25%-design filing with MassDOT. The Town paid Azzalina and his team to analyze a four-lane configuration.

That analysis, including the above diagram, is on pages 31–34 of the FDR, which you can read here.

Even under the best possible 4-lane design there are only 14 feet available for  each shared lane, and that’s not enough.

I summarize this analysis and, in a separate post, the “encroachment” issue, but the FDR has the companion drawing to the one above showing how a 3-lane configuration is safer. (There’s more room for everyone.)

At the hearing, Azzalina’s remarks were followed by an explanation from Frank Suszynski, project engineer at MassDOT, of his department’s bicycle-accommodation requirement. (Transcript 76.14–77.20, excerpted here.)

MassDOT wants 15-foot shared lanes (16 feet preferred) next to parking, and there is only room for 14-foot lanes. Thus Azzalina’s remark about needing “to narrow the sidewalks” for a 4-lane design.

Suszynski says that not only does MassDOT prefer bike lanes when possible, in this case shared lanes are not feasible because, as Azzalina shows, they are not safe.


No comments yet

What do you think?

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: