The current scope of the I-270 and I-495 widening project proposed by Gov. Larry Hogan's administration. Credit: Maryland Department of Transportation

In recent months, the Maryland chapter of the Sierra Club and Rockville city officials submitted public information act requests to the state, seeking traffic modeling data for a controversial project that would widen parts of I-270 and I-495 with two toll lanes in both directions. 

Both parties were informed recently by the Maryland State Highway Administration that fulfilling their requests would cost thousands of dollars.

Initially, the project proposed by Gov. Larry Hogan called for widening all of I-495 in Montgomery and Prince George’s counties as well as I-270, and building four toll lanes, two lanes in each direction. But the Maryland Department of Transportation announced last year that the first phase had been narrowed to include only replacement of the American Legion Bridge, the westernmost section of I-495 leading to I-270, and north on I-270 to I-370 – at a cost estimated to be $3.75 billion to $4.25 billion.

The proposal has been controversial, with Hogan and supporters saying it is needed to relieve traffic congestion in the region, while opponents say it will be harmful to the environment and not actually reduce congestion long-term. The Federal Highway Administration just approved a environmental impact statement for the project, making it eligible for federal funding.

According to the agency’s response, the Sierra Club’s request for the project’s traffic modeling data, sent to the SHA in late June, would require about 238 staff hours and cost an estimated $21,796. Rockville’s request, sent in early August, would require roughly 73 staff hours at an estimated cost of about $11,848.

In SHA’s responses to both requests, officials noted that fulfilling them would take a review of thousands of emails and the release of a large amount of records.


Terry Owens, a SHA spokesperson for the I-270 project, wrote in an email that the scope of both the Sierra Club and Rockville’s requests were broad.

“[Maryland Department of Transportation’s] SHA offered to work with the requestors to focus the scope of the request on specific records sought and to limit the cost,” Owens wrote. “MDOT SHA also provided significant information as part of the Draft, Supplemental Draft, and Final Environmental Impact Statements that we encouraged the requestors to review to help narrow the scope and costs of the request. As of today, we have not received a narrowed scope from the requestors.”  

Josh Tulkin, director of the Maryland chapter of the Sierra Club, said the organization didn’t pay to fulfill the request because the estimated cost was too high. But Rockville city officials said recently that the city would pay the roughly $11,848 fee in order to access the data. 


Craig Simoneau, Rockville’s director of public works, said in an interview last week that city officials would need to hire a consultant to parse through the data, given the software it requires and the technical expertise involved. 

The Sierra Club and Rockville officials wanted to review the data to make sure the traffic modeling is based on accurate assumptions and information, as well as to see if it is comparable to data that would show the impact that the coronavirus pandemic has had on overall commuting in the region.

Rockville Mayor Bridget Donnell Newton and the City Council voted in early August to authorize Simoneau and city officials to send the request to SHA. Simoneau and City Manager Rob DiSpirito told council members at that meeting that the city would be willing to pay thousands of dollars if that’s what SHA officials requested for the data.


“This is not something that’s going to strain the city’s budget … the city manager and I both said we’ll find the money to pay for this MPIA request,” Simoneau said in an interview.

City Council Member Mark Pierzchala said in an interview that he thinks the money is a sound investment. Rockville, Montgomery County and the Washington Suburban Sanitary Commission — the water utility for Montgomery and Prince George’s counties — may be required to make considerable improvements, such as utility relocation and other infrastructure improvements, as part of the project, he said.

“I think it’s an extremely good expenditure, considering the city may be on the hook for millions of dollars,” Pierzchala said.


What information did Rockville and the Sierra Club request?

The public information requests submitted by Rockville and the Sierra Club were similar, but not identical. Both asked state highway officials for the project’s traffic modeling data to gauge how the widening of parts of I-270 and I-495 and the replacement of the American Legion Bridge would impact traffic.

Rockville’s request included all of the “input data” that went into assumptions and traffic projections for VISSIM — a popular traffic simulation software — and any other traffic modeling software. That information has helped inform the I-270 and I-495 managed lanes study, which looked at how to best address congestion in the traffic corridor.  


Pierzchala, a professional statistician who has worked on major federal government surveys and data collection, said he doesn’t have the knowledge or expertise to understand or interpret this underlying data. But he added that — on the broader issue of traffic modeling and data analysis — it should be easy to reproduce. 

He questions why it should cost so much for the SHA to provide the data.

“Here you have a scientific process which is modeling, and people ought to be able to replicate it, and you should make it easy for people to replicate … . The modeling should be extremely transparent, all the data that go into it, all the assumptions that are made. All the adjustments, and all of that should be documented as they go along,” Pierzchala said in an interview. 


Norm Marshall, president of Smart Mobility, a transportation consultant, agreed. The company assisted with the Sierra Club’s request. 

The organization’s request was more detailed than the one submitted by Rockville officials, including asking for several specific aspects of SHA’s data with the VISSIM modeling, as well as some output data the state used from the Metropolitan Washington Council of Governments (MWCOG) to determine peak morning and evening commute travel demand tables, among other requests.

Marshall said in an interview that he has done similar work nationwide, and that similar traffic modeling data has been provided free of charge or only cost hundreds of dollars. 


The underlying data can be complex, but it can show how state officials used the traffic modeling software, Marshall said, and can answer questions including:

  • How much space was provided between individual cars in the model?
  • What’s the overall behavior of certain cars and drivers? 

“They do microsimulation where they’re actually modeling each car separately. Each car is treated as an agent [in the modeling],” Marshall said. 

Despite the size of Maryland’s project, state officials should be able to provide the data for free or cheaply, he added.