When four lanes won’t fit


When the engineers hired by the Town assessed the feasibility of four striped lanes on Mass. Ave., they ran into a problem.

The lanes don’t quite fit, if parking is included.

The road “is essentially constrained to a 66-foot width” curb to curb (Functional Design Report, p. 32).

The four-lane plan drops the bicycle lanes, but in doing so incurs a requirement that the right lanes be at least 15 feet wide because they are shared (citing, at page 33 of the FDR, MassDOT’s Project Development and Design Guide).

A 15-foot shared lane plus an 11-foot left travel lane times two (for both sides of the street) would take up 52 feet, leave room for only 7-foot-wide parking lanes. This is unacceptable, so the engineers instead modeled 14-foot shared lanes and 8-foot parking lanes, as follows:

Parking 8 ft.
Shared 14 ft.
Left 11 ft.
total 33 ft. (half of 66 feet)

The engineers found the following flaws with this scheme:

  • With 8-foot parking lanes, “the door zone of parked vehicles would encroach into the right-side, shared-use lane of a four lane cross section” (p. 33)
  • “the four-lane, shared-use cross section does not allow enough space between the door zone of a parked vehicle and a bus traveling in the right-side travel lane” (pp. 33, 34)
  • Due to insufficient space, drivers in the right lane would regularly “encroach” on the left, so that “a marked four-lane facility would actually operate more like a three lane facility” (p. 34).

(I look at this last point in a bit more detail in a previous post. One takeaway is that what seems to work in today’s amorphous “super lane” is more troublesome once you mark separate lanes.)

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

There is no reason to suppose that MassDOT would accept this unsatisfactory result, with its 14-foot shared lane where 15 are usually required.

The Town instead proposes wider parking lanes and a host of pedestrian-safety improvements. Dedicated bike lanes make possible standard-width 11-foot travel lanes. Everything fits into 66 feet because the outbound traffic requires only one lane (for more on this see the FDR on pp. 31-32).

Read the FDR and judge for yourself. It’s online at the Town’s web page for the Mass. Ave. project.


8 comments so far

  1. Eric Berger on

    There you go again! Stop misinforming the public! Page 33 of Chapter 5 {you failed to mention it was Chapter 5 of the Desighn Guide you were referencing) of the Mass. DOT’s “Project and Development and Design Guide” states nothing about 15-foot shared travel lanes being required on a four-lane highway, and you know it. Exactly where on that page is that stated? I’ll tell you where…no where.

    However, a sentence in a section titled “Shared Lanes” on Page 23 of Chapter 5 of the Design Guide, a page you have also read, states that “Lanes at least 14 feet wide are generally wide enough to permit motorists to pass bicyclists without changing lanes.”

    Assume a public conscience, if you have it not.
    Eric Berger

    • Adam Auster on

      Eric, it’s on page 33 of the Functional Design Report that the engineers (not I) cite the Design Guide. If I’d been citing the Guide myself I’d have put it differently.

      I agree that this is not clear enough, and will edit the cite. (The original, which Eric reacts to above, had said “citing, at page 33, MassDOT’s Project Development and Design Guide.”)

      The part of the FDR I was citing (at 33) reads as follows:

      Although current bicycle guidelines referenced in MassDOT’s 2006 Project Development and Design Guide indicate minimum widths of bike lanes and shared use lanes should be 5 feet and 15 feet, respectively, when adjacent to on street parking, the width of the shared use lane was limited to 14 feet because of the existing roadway constraint (i.e., 66 feet curb to curb).

      The authors regrettably do not source their citation of the Guide with a page number. I would be cautious however about assuming that your quote from 5-23 of the Guide is a smoking gun that refutes the engineers’ conclusions. The engineers may just be guilty of a poor citation.

      The authors may have another source they failed to cite. See for example Mass. Highway Engineering Directive E-09-05, which seems to require 16 feet. Or they may simply be summarizing their own finding (on 33-34) that 14 feet does not work on Mass. Ave. Which it clearly does not.

      I don’t imagine that you and I agree on much, but I am genuinely grateful for the chance to fix a cite that was not very clear. Thank you for bringing it to my attention.

  2. Eric Berger on

    You’re welcome.

    Now please fix the numerous examples of misinformation about what the EACCC and I want regarding the Mass Ave. corridor, misinformation that was published in the “study” authored by Chad and you, the gist of which also appeared in the Letter to the Editor that Chad and you wrote that appeared in the current issue of “The Arlington Advocate”.

    Imagine if I made up things about Chad and you and the EALS Coaltion and published that material as if it were the truth. The Golden Rule is an excellent ethical canon.

    Adam, let’s face it: you know exactly what the East Arlington Concerned Citizens Committee(EACCC) and I want. We’ve stated it over and over since 2009. To maintain public safety for our community, we want to retain the existing roadway with these existing widths: two 14-foot wide shared travel lanes, two 11-foot wide travel lanes, and two 8-foot travel lanes. We want the travel lanes striped so everyone knows where each lane’s width begins and ends.

    What we want is also what the over 2,500 residents want who’ve signed the EACCC petition opposing the Selectmen’s plan to remove two travel lanes and replace them with two 5-foot bike lanes. It’s what 82 (74%) of the businesses want that are located on the corridor.

    You know maintaing the existing widths of the four travel lanes and two parking lanes doesn’t require adding anything. You wanted to confuse people with misinformation. That’s unethical Adam.

    Imagine if I said that adding the two bike lanes means parking would have to be eliminated on one side of Mass. Ave., and then concocted some story, juxtaposing data to make that false accusation seem true. You’d feel furious and call me to task, and rightly so! How dare I misrepresent the EALS Coalition! One’s ends don’t justify unethical means.

    I respect that you did not delete my previous comment and hope you won’t delete this one either. Censoring comes home to roost, even in a place like Egypt.

  3. Eric Berger on

    In my previous comment I made a mistake. The EACCC and I want to retain on the corridor the existing two 14-foot wide shared travel lanes, two 11-foot wide travel lanes, and two 8-foot wide parking lanes. In the previous comment I mistakenly wrote two 8-foot wide travel lanes instead of two 8-foot wide parking lanes.

    • Adam Auster on

      So you want 8-foot parking lanes, 11-foot travel lanes, and 14-foot shared lanes?

      And you are speaking for the Concerned Citizens Committee?

      From my point of view, that clarifies a lot. How could anyone “know exactly” what your group wants, when it has issued so many public statements that directly contradict the lane widths you now say you favor?

      You yourself spent a good deal of effort last fall criticizing the 10-foot parking lanes proposed by the Town as too narrow.

      Your group attacks 11-foot travel lanes as narrow and dangerous in the leaflet you have been using to collect signatures on your petition.

      I am glad you have clarified your group’s position.

      However, any reasonable reader would take the earlier criticisms to mean that the CCC is not satisfied with even 10-foot parking lanes (let alone 8-foot ones) or with 11-foot travel lanes, and wants both to be wider.

      That’s not an unfair conclusion to reach, based on your own statements. Indeed your clarification sounds like a change of policy to me.

  4. Eric Berger on

    Stop making stuff up! You’re not the least bit confused.

    • Adam Auster on

      No need to be so prickly, Eric.

      Why not clear up some of the confusion by squaring the CCC’s (1) support of the 8-14-11 lane configuration with (2) its claim that 11-foot travel lanes are too narrow and increase the likelihood of accidents?

      Or with your own campaign last fall against 10-foot parking lanes on the grounds that they, too, were not wide enough?

      You called them potentially “deadly” because of their width, but now you support parking lanes that are only 8 feet wide.

      It is not unreasonable to ask what all that means in light of your new position.

      In any case, what do you say to the Town’s critique of your 8-14-11 lane configuration?

  5. Eric Berger on

    I don’t answer dishonest, straw man questions. Why do you misinform, Adam? Assume a public conscience if you have it not.

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: