Casey traffic data accuracy is in doubt

June 8, 2012
By

FOREST HILLS—Discrepancies between two Casey Arborway traffic analyses—one publicly released, one not—have been discovered by critics. They show traffic performance to be worse in most cases and better in others than the state previously announced.

It is unclear why the new information and traffic data previously presented to the advisory group do not match.

“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,” said Design Advisory Group (DAG) member Allan Ihrer. “The ultimate goal is to figure out where there are problems and fix them if we can.”

MassDOT did not provide comment about the discrepancies by the Gazette’s deadline.

The traffic analysis, created by a computer modeling program called Synchro 7, shows projected levels of service (LOS) at different levels than what the state Department of Transportation’s (MassDOT) design team presented to the community during earlier traffic discussions. LOS is a measure of how well traffic moves through an intersection.

Traffic data was crucial in the state’s decision to demolish the overpass and rebuild the Arborway as a surface street last year. According to the state’s traffic analysis, either a replacement overpass or surface streets would be able to cope with projected levels of traffic in 2035.

The Synchro analyses were only released in response to a Freedom of Information Act (FOIA) request filed by DAG member David Hannon. He had to wait over six weeks to receive them, he told the Gazette.

FOIA is a law that provides for the disclosure of documents controlled by the government, following the idea that the public has a right to see them.

Hannon said he filed a FOIA to access these files so that “we could assess the veracity of DOT’s conclusions…I’m not sure whether DOT is acting purposefully or just negligently. Neither alternative is promising.”

The data compares LOS during the morning and afternoon peak hours—the two hour-long periods during the day when traffic is at its heaviest.

LOS scores go from A to F and measure how long a vehicle must wait at a given intersection. While LOS A describes an empty and free-flowing intersection with less than 10 seconds of wait time, LOS D (up to a 55-second wait) and E (up to a 80-second wait) are acceptable in large urban areas, especially during peak hours.

According to the design team, the LOS scale is the industry standard, which is why they use it despite its shortcomings.

In a list compiled by Ihrer, two Synchro analyses provided in the newly-released documentation did not match data concerning the seven intersections affected by the project previously given to the DAG.

Some, though not all, discrepancies show slower intersections—or lower LOS scores. For example, the intersection of New Washington Street and Washington Street was presented as having a LOS of C for both the morning and afternoon peak hours. Two different Synchro analyses show that intersection with LOS in the D-E-F range, a significant drop from the state’s presentation.

Ihrer believes the design team is “playing fast and loose with the facts,” he said in a letter to MassDOT, a copy of which he provided to the Gazette. After nine months of seeing their evaluations, “We are finally told by the traffic engineer that these don’t effectively show roadway and intersection performance.”

The design team is scheduled to hold a traffic discussion with the DAG on June 18. There is also the possibility of a second meeting being scheduled for more in-depth discussion.

The Casey Arborway, an at-grade surface street network, will replace the crumbling Casey Overpass. The Casey Overpass is the State Route 203 bridge over Washington Street at the Forest Hills T Station. The process has been fraught with controversy since it was first announced in late 2010.

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  • JonFrum

    Nothing to see here – keep moving, you lot! 

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