Snow and Mass. Ave. geometry

I’m writing this on February 9 after a day of digging out from a pretty big storm. My little street did not even get cleared until about 4 pm, at which point the town had to use an earth mover, not a plow.

2011: Residues of the scraped-away ice show how much the road had been constricted. West on Mass. Ave. from Henderson St.

But, remember the snows of 2011? We had a lot of them, and there was some melting and refreezing.

By the time it became clear that the strategy of just shoving snow to the sides of the streets was not going to do it this time, the stuff was too dense and frozen to plow.

Some side streets were really choked, and Mass. Ave. itself was down to one lane in each direction. This really slowed things down inbound (outbound was fine).

With more passion than logic, opponents of the redesign began to cite this experience as proof that the new layout for the street would be a failure. Whereas in fact

  • even at the height of the road constriction, westbound traffic from East Arlington to Arlington Center ran as usual;
  • the design provides for two eastbound lanes, same as today. (Actually better, see below.)

Leaving that aside, though, is there anything that the one-lane-each-way experience of 2011 tells us about traffic and new design of the street? What can we actually learn from it?

And, as a separate question, which design would handle those conditions better—the one we have now, or the one that is in the works?

The answer to the first question is not difficult. As both traffic counts and direct experience shows, westbound traffic is light enough to get by with a single lane. The experience on Mass. Ave during the one-lane period further confirms this.

Proposed lane configuration

Proposed

Eastbound, where the morning peak is more acute, would suffer, but in exactly the same way as in 2011. Because there are still two eastbound lanes in the design.

So which design is better at coping with crippling snow?

Not only are there still two eastbound lanes in the new design, but they are offset towards the center of the street. The whole eastbound side is four feet wider (33 feet today, 37 planned).

It’s asymmetrical.

Consequently, the new design copes with extreme snow accumulation better.

New design, with wider eastbound side, keeps all lanes out of the snow zone.

New design, with wider eastbound side, keeps all auto lanes out of the snow zone. Based on official drawings showing 10′ parking lanes, 5′ bike lanes, two 11′ travel lanes, and one 14′ lane westbound. Shading indicates 15′ of snow per side.

The current symmetrical design, with no lane markings, is only 33 feet eastbound. It gives space to a second westbound lane that is not needed.

Under extreme snow conditions this leads to single-lane driving behavior.

The proposed design is 4 feet wider eastbound, keeping both lanes further from the frozen snow. Meanwhile one lane is more than adequate for traffic westbound.

This is another benefit of the redesign that would be impossible under a four-lane configuration.

Three blocks of Mass. Ave in the business district have a slightly different design that accommodates two pedestrian safety islands and a flush median strip. Here the center islands shift all lanes 2 feet towards the curbs.

The snow benefit is thus not a great as in the other blocks, though still better than what we have today. (And the flush median would be traversable in an emergency.)

It’s important not to get too excited about this, since the real bottlenecks inbound are in Cambridge. But in every respect the new design works better with the snow than the one we have today.

Advertisements

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 )

Twitter picture

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

Facebook photo

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

Google+ photo

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

Connecting to %s

%d bloggers like this: