23 seconds

StopwatchTrips along the Town’s 3-lane design for Mass. Ave. in East Arlington will take about as long as on a 4-lane alternative, according to a controversial new software model.

The Town’s consultants performed the analysis even though the Mass. DOT has found 4 lanes to be unsafe and unacceptable.

Safety aside, both designs perform similarly in terms of average trip times. That is what you would expect based on the traffic data, which show that the 3-lane design meets peak traffic as well as a 4-lane design.

Bu that’s not what you might have thought from reading the January 23 letter from the Federal Highway Administration to MassDOT.

Federal Highway, which requested the analysis, noted that evening-peak inbound traffic in 2028 could take 59 seconds longer to drive Mass. Ave. in East Arlington under the new design compared to a “no-build” scenario in which nothing changes.

Westbound, the FHWA said, the increase could average 34 seconds, again in the evening peak compared to “no build.”

The FHWA seemed to scold MassDOT when it noted it had already made these points “in our prior December 12, 2012 e-mail correspondence to the project manager.”

Net change: a minute and a half (59 + 34 seconds).

MassDOT replied on February 14 that the relevant comparison is not to the “no-build” scenario, but to a 4-lane design. Apparently FHWA asked that the new software model such a design late last year.

MassDOT notes that rather than being 59 seconds slower than a 4-lane design eastbound, the plan would be 3 seconds faster. Westbound the delay is 26 seconds, not 34.

Net change: 23 seconds.

Futhermore, MassDOT says (reply p. 3), “a portion of this time [26 seconds] is expected to be offset by other proposed improvements that…are not reflected by the multi-modal analysis.” These include the positive effects that bicycle lanes will have on traffic flow (reply p. 10).


MassDOT hearing February 26

Oh, and this reply is prefaced (bottom of p. 2) by the phrase, “As discussed in FST’s memorandum dated December 13, 2012.” In other words, FHWA had this information already. (FST is Fay Spoffard & Thorndike, the Town’s engineering consultant for the project.)

The politics of this are fascinating. This is the same letter that essentially forced a second design hearing on February 26 and delayed the project by 3 months.

Perhaps the strongest element of MassDOT’s response is the following from page 2:

It is very important to note that proposed 4-lane section constructed within the existing roadway curb-to-curb dimension does not meet current state standards and would require State and Federal Approval of a Design Exception.

MassDOT has consistently made this point to all comers throughout this process. MassDOT also enumerates benefits to pedestrians, bus transit, and cyclists:

In order to pass a bicycle in the nobuild or 4-lane alternative, vehicles would need to change lanes or encroach into the leftmost travel lane as they currently do today…. Under the no-build and 4-lane alternatives, bicycles will impede traffic while traveling in substandard-width shared lanes.

Again, this is not news to anyone who has been following this project.

The increase in trip time for both 3- and 4-lane options versus the “no-build” scenario is almost certainly attributable to the new signal at Bates Road (added to improve traffic flow for entering vehicles).

The greater delay eastbound, where both designs propose 2 lanes, probably reflects interactions between the Bates signal and the one upstream at Foster and Linwood.

The new signal at Bates Road causes delays for some but speeds traffic for others and adds a pedestrian crossing.

A new signal (S) at Bates Road causes delays for some but speeds traffic for others and adds a pedestrian crossing.

The 3-second improvement eastbound (versus 4 lanes) is probably from the dedicated left-turn lane onto Winter St., something made possible by the asymmetric 3-lane design.

The 26-second delay westbound may be in part due to the elimination of 3 left-turn lanes west of Linwood St., one of the many benefits sacrificed when the Town added a second eastbound lane to that stretch last year.

These times are all for the evening peak hour in the year 2028. They describe average trip times for someone driving the entire mile-long project.

The 3-lane design provides significant pedestrian-safety improvements that do not fit if there are 4 lanes.

Trip-time was, with public participation and traffic merges, one of three issues raised by FHWA in its January 23 letter. I describe the other two of those issues in this post.

Since “no build” is not on the table, I can’t help but conclude that the January letter, with its exaggerated delays, overstates the problem.

The new signal at Bates Road, which is presumably the source of the increase for both 3-lane and 4-lane options, provides a new signalized crossing for pedestrians and eases traffic entering from the cross streets, another thing not counted in the new analysis.

Traffic signals are a usual response to heavy traffic in residential neighborhoods and the delays they introduce are a consequence of the traffic volume that makes them necessary in the first place.

I imagine the 23 seconds (or 26, if you do not count the eastbound benefit) may become a rallying cry for opponents, who regularly decry the “parking lot” that Mass. Ave. will become under the new design. At least now we know what they mean by that.

Stopwatch image courtesy of Julian Lim; Bates signal detail from 25% plan drawings.


2 comments so far

  1. Mark Kaepplein on

    The 23 seconds or 59 seconds are inaccurate. Those figures rely on two bad assumptions. One, that westbound, three lanes NEVER form when the light is red at Lake Street and there is not a separate left turn lane with two through lanes. The simulation assumes there is only room for two lanes where the road is 82 feet wide. The FST simulations also assume the bus stop in front of the Capitol operates also as a right turn lane now and in their proposed design. When the fed asked FST to simulate a 4 lane design, they again simulated no left turn lane for Lake despite copious width. The feds will weigh in on these issues.

    The Linwood intersection does not meet warrant requirements to have a light there. A closed doors meeting made it stay. The intersection at Bates does meet requirements, but is just two short blocks from Linwood. Seems stupid to keep both. Make Linwood just a pedestrian signal, not a full traffic signal.

    Note, half the project money is targeted at reducing traffic congestion and improving air quality (CMAQ). Time of vehicles sitting idling needs to be reduced compared to not spending any money,

    Has anyone compared current driving times with what simulations claim to verify accuracy? As bad as simulations are, there are not even any estimates for how many fewer accidents will occur with various safety features.

    • Adam Auster on

      Residents at the 2009 Hardy School advocated strongly to keep the Linwood/Foster signal (and the Teel/Thorndike signal).

      Rightly or wrongly, this was a community concern and the Hardy School meeting was did not take place in secret.

      You are probably right that forgoing these signals would speed traffic along Mass. Ave., but (a) at the expense of entering traffic and (b) probably doing so equally for both 3- and 4-lane designs.

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