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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.]

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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