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How Accurate Are the State's Casey Arborway Traffic Projections?

Residents and politicians watching the design of the new Casey Arborway say the state still hasn't put to rest concerns about gridlock.

Some of the residents who pay the closest attention to the massive Casey Arborway project — JP's equivalent of the Big Dig — remain unconvinced the state's traffic analysis is accurate.

The most recent meeting of the Design Advisory Group with state transportation officials was supposed to clear the air about traffic concerns. The state plans to tear down the Casey Overpass, which handles 24,000 cars a day, and remake the area with a six-to-seven lane network of surface roads.

The state maintains that either of the proposed solutions — building a new, smaller bridge or the at-grade solution — .

State Representative Russell Holmes, D-Boston, spoke for the unconvinced at the May 24 meeting. When Gary McNaughton of the State Department of Transportation urged those with doubts to "go to the Web site," for traffic information, Holmes pounced.

"That's the problem right there," Holmes said to the packed room at the State Labs on South Street. "I know you feel comfortable but I don't think you're hearing what the community is saying."

Further doubts were sown upon revelation that skeptics had been forced to file a Freedom of Information Act request to get the detailed traffic data used by the state to inform their analysis.

The Gazette reports that the data from that request shows some intersections would work worse than the state's projections under most cases, though some intersections would actually be better than the state's publicly-announced conclusions.

"I’m not trying to be alarmist, but if we’re going to have an hour of gridlock, I’d like [the design team] to say we’ll have an hour of gridlock," Design Advisory Group member Allan Ihrer told the Gazette. "The ultimate goal is to figure out where there are problems and fix them if we can."

A key misstep by the state, according to Holmes, was deciding not to do a detailed analysis of current traffic conditions in Forest Hills. That means there's no baseline against which to compare the state's projections for traffic in 2035.

Transportation officials use a measure called "Level of Service" to rate traffic flow. It runs from A (best) to F (worst). For urban areas, D is considered acceptable, McNaughton said. If the state did nothing to change traffic patterns in Forest Hills, McNaughton said, intersections would be F into the future.

"You certainly have F out there today," McNaughton said.

The Gazette pointed out that the underlying data for the intersection of New Washington and Washington yields results in the D-E and F range for rush hour. Yet the state said publicly that the intersection would perform at level C at those times of the day.

State officials say the at-grade solution can handle all the traffic because of various improvements:

  • Roads will be much more organized
  • The lack of left turns will allow better spacing of traffic signals (people will change direction via "bow tie" turns in which you go past an intersection and loop back.)
  • "Through movements" will actually be "through movements"

"The existing pattern is nearly impossible to synchronize," McNaughton said.

[Editor's note: The lede of this story was changed to reflect that fact that it is only some of the residents who most closely follow this project who doubt the traffic projections.]

Pete Stidman June 08, 2012 at 05:52 PM
In urban situations, many traffic engineers will tell you that even LOS F is acceptable. As McNaughton pointed out, we have F out there in some places today. People who drive in the city cannot expect neighborhoods to keep widening roadways ad infinitum just to save them an extra 30 seconds at a stoplight. I am frankly disappointed that a small group of Jamaica Plain residents are still working to disrupt the DAG planning process despite the vast majority who want to move this project forward. We have long passed the decision stage between bridge and at-grade, and turning back now threatens funding for the entire project regardless of what we change or do. As to these frivolous stories that include no comment from the state or from any at-grade supporters (totally one-sided reporting folks), if the state studied a variety of situations and ran a number of simulations on the Arborway area—it just tells me they are doing their job. I haven't asked, but after numerous conversations with the engineers including Gary, I can imagine they went with the numbers they felt most confident with. You can't expect them to go through all 100 hours of explanation for every detail they looked at along the way. I certainly wouldn't want to sit through it. And in any case, predicting future traffic situations is not a perfect science, but instead a very educated guess. I predict our neighborhood will be greatly improved by increased economic development and quality open space.
Charlie Denison June 08, 2012 at 06:17 PM
I think It's really important that we not let future traffic projections have such a large impact on what we build today. Traffic engineers have always assumed that traffic volumes will go up, but recent history is changing that assumption. Over the past 5-10 years, traffic volumes in Boston (and the US as a whole) have leveled off and are going down, even as more development has taken place. (I suspect if we compared the future traffic projections from the past with the actual volumes of today that those projections would be wildly off. What's sad is that transportation agencies never actually go back to see if their projections were correct!) We should respond to these declining traffic volumes by building a road that serves today's traffic and only building the lanes we need right now -- and perhaps, if we really feel the need, that can be easily adapted to serve more in the future. If people are afraid of traffic congestion, the worst solution is to build a big road with many lanes. That will only encourage more traffic (and more speeding during the non-peak times) where what we all want is a properly-scaled city street that serves everyone well.
Michael Halle June 08, 2012 at 06:38 PM
Just a couple of corrections to the article. First, it says, "The most recent meeting of the Design Advisory Group with state transportation officials was supposed to clear the air about traffic concerns." The purpose of the meeting was to provide a traffic primer for new people joining the Design Advisory Committee, essentially a recap of MassDOT's previous presentations in one short meeting. Second, the article states, "A key misstep by the state, according to Holmes, was deciding not to do a detailed analysis of current traffic conditions in Forest Hills. That means there's no baseline against which to compare the state's projections for traffic in 2035." I don't remember this particular comment from Rep. Holmes, but there certainly was a detailed traffic analysis of current conditions. The fact that some may not trust the accuracy or completeness of that analysis doesn't mean it wasn't performed, or that others in the community don't feel it sound. I would also take issue with the blanket statement, "The residents who pay the closest attention to the massive Casey Arborway project — JP's equivalent of the Big Dig — remain unconvinced the state's traffic analysis is accurate." There are some such residents; it is not surprising that you would hear from the people who are unconvinced. Other highly-involved DAG members are sufficiently convinced and are mostly looking beyond additional analysis to working on plan specifics.
Chris Helms (Editor) June 08, 2012 at 07:06 PM
Thanks for the clarifications, Michael. That's what I understood Rep. Holmes to say. And I think you make a good point about it being "some" of the residents who, like you, pay the most attention and are most knowledgeable about this project. I'll update the story lede.
Liz O'Connor June 08, 2012 at 08:37 PM
Pete, I am not worried about an extra 30 seconds at a stoplight. I am concerned that the data they used to model the at -grade solution is not good enough to produce a real estimate of the gridlock we're inviting to Forest Hills, which in turn will a) make it really hard for people to get to work, b) decrease air quality and c) create a vast spread of pavement for peds to cross to get around FH. I am agreed that the decision is made and it is time to move forward. My own current concern is that unless we insist on correcting flaws in the traffic data (for example that the baselines were collected in summertime when traffic is much much lighter than winter and when roads are clear of snowbanks and school buses), we will be building our at-grade solution on bad information which is likely to lead to a worse design. I'd think that you'd support the effort to get a handle on the real numbers - information which is both useful and available, and then re-run the models based on that and the design changes (i.e. left turns allowed) which have come since the modeling was done. What is the basis of your opposition to this request?
Heather Carito June 08, 2012 at 10:20 PM
Yes, the decision has been made, but if the decision was based on incomplete or flawed data, I think that's a problem. Better to get all facts on the table and be clear that a well-informed and unbiased decision was made than to wait until we're in the middle of construction to realize that it was not. Less than 4 years ago the SGH Project's Structural Condition Investigation and Traffic Study concluded that "traffic volumes would overwhelm any at-grade intersection configuration, resulting in poor levels of service, excessive delays, and probable gridlock. The Arborway should remain in a grade-separated configuration." Why is this comprehensive study being ignored? And a recent Boston Business Journal ranks Boston as the 8th worst US city for traffic congestion. One of the 3 worst bottlenecks in the metro Boston area is Rt 203/Gallivan Blvd. which is about 2 miles from Shea Circle. My point is only that all studies should be carefully considered before it is too late to make changes.
Alan Wright June 09, 2012 at 04:23 PM
Bravo Charlie
Michael Halle June 10, 2012 at 04:56 AM
Heather, The 2008 plan hasn't been ignored. The 2008 report just didn't consider the current at-grade proposal, which is both more efficient and far simpler than the report's proposals. When questions were raised about the 2008 report last year, I read it and provided some commentary here: http://mikes-casey.jpma.us/2008-casey-overpass-study-a-closer-look In summary, the 2008 report, created without public input or review, focused narrowly on how to replace the Casey Overpass. The report was created before MassDOT took control of the structure and before additional bridge inspections revealed exactly how bad a condition it was in. The final 2008 recommendation would have perpetuated the current frustrating conditions for drivers, pedestrians, cyclists, and transit users for another 75 years, or in some ways even made them worse (even dreadfully worse). Look at my summary or read the entire report yourself. I believe none of the 2008 report recommendations (at-grade or bridge-based) would have survived public review. It's then hard, at least for me, to assign credence to a specific comment from the report like "there's too much traffic for at-grade intersections", let alone call the report "comprehensive", without starting from first principles like the 2011 process did.
Allan Ihrer June 13, 2012 at 04:35 PM
Why is JP being denied the chance to find and hopefully fix problems with our Casey Arborway At Grade? This is ignorant ignorance. Below are two year 2035 AM/PM commutes. There are very bad spots and not so bad spots. Note, these numbers are based on traffic counts made during a recession when universities + private schools were out for summer vacation. AM westbound commute across Forest Hills Casey Arbor./Cemetery Rd.: wait = ? mins,queue= ? ft, LOS = ? Casey Arbor./Forest Hills Dr.: wait = 4:37 mins,queue=~533 ft *,LOS = F Casey Arbor./East Bow Tie: wait = 0:24 mins,queue=~521 ft, LOS = C Casey Arbor./Hyde Park Ave: wait = 1:19 mins,queue=~591 ft *,LOS = F Casey Arbor./South St.: wait = 0:20 mins,queue=~237 ft, LOS = C ~ Volume exceeds capacity, queue is theoretically infinite. * Queue backs upstream into previous intersection. LOS is Level of Service A = good, F = bad PM eastbound commute across Forest Hills Casey Arbor./West Bow Tie: wait =0:38 mins,queue= 578 ft, LOS = D Casey Arbor./South St.: wait =0:36 mins,queue= 394 ft, LOS = D Casey Arbor./Hyde Park Ave: wait =1:01 mins,queue=~838 ft *, LOS = E Casey Arbor./East Bow Tie: wait = ? mins,queue= ? ft , LOS = ? Casey Arbor./Forest Hills Dr.: wait= 0:11 mins,queue= 91 ft, LOS = B Casey Arbor./Cemetery Rd.: wait = ? mins,queue= ? ft, LOS = ? And what about the famous Eggabout; might it improve traffic conditions?

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