Oh, God No

State eyes double deck for top-end I-285

Atlanta Business Chronicle
by Ryan Mahoney, Staff Writer

State road planners are considering double-decking Interstate 285 on the heavily traveled north side of Atlanta between I-75 and I-85.

The Georgia Department of Transportation is working to develop a 25-year expansion plan for the 10-lane perimeter highway, which it hopes to have completed by the end of 2006.

One possibility is adding four truck-only toll lanes in the middle of the heavily traveled northern stretch of I-285, with four high-occupancy-vehicle or high-occupancy-toll lanes over them.

As many as 250,000 vehicles a day jam the 13-mile northern section of I-285 between I-75 and I-85, making congestion relief there one of GDOT's top priorities.

To that end, the department has been looking at building high-occupancy-vehicle lanes, truck-only toll lanes and bus rapid transit lanes on part or all of I-285 since 2004. The road was last widened in 1996.

In the last few months, though, planners also began investigating the possibility of building raised lanes above the center of the roadway on the north side.

GDOT will take "a long hard look" at the concept, said Chief Engineer David Studstill.

Building elevated lanes would minimize both the high cost and the time required to buy right of way, as well as reduce the displacement of residents and businesses along the route. The cost of acquiring land often equals -- and can far exceed -- construction costs in urban highway projects.

Other cities with double-decked roads built or under consideration include Austin, Houston and San Antonio, Texas; Birmingham, Ala.; Los Angeles; New York; Seattle; St. Louis; Tampa, Fla., and densely populated areas in Europe and Japan.

Right-of-way acquisition aside, the actual construction price tag for such elevated highways is typically three to four times that of those built on the surface. It is unclear whether overhead lanes would be cheaper on I-285; both right-of-way prices and costs for asphalt, concrete and steel are soaring.

Post, Buckley, Schuh & Jernigan Inc., the firm which is studying the concept for GDOT, has not performed a cost comparison. But Bill Jordan, a project manager at PBS&J, said the idea has merit.

"You'd have to add eight lanes on the ground otherwise," said Jordan. "This reduces the right-of-way by half."

History and funding

The idea of double-decking Atlanta interstates is not new. In the 1980s, GDOT toyed with double-decking the four-mile core of the Downtown Connector before it was rebuilt, but abandoned the concept because of concerns about cost. It began exploring the possibility again in the late 1990s.

The late developer Kim King, who built office buildings along the Downtown Connector in Midtown, also looked at double-decking part of the Connector between Fifth and 10th streets, Jordan said.

Going up would be the only way to add real capacity to the oft-bottlenecked Connector, GDOT engineer Studstill said. Expanding outward would require tearing down multimillion-dollar skyscrapers and paying accordingly for the right to do so; the same is true to a lesser extent on I-285. Digging down is not an option, he said, citing Boston's Big Dig, which ended up costing more than $1 billion per mile.

Studstill said any second deck on the Downtown Connector would probably have to soar as high as Spaghetti Junction to clear the Connector's existing bridges and interchanges -- rebuilding all of them to tie in would break the bank -- and would likely function as an express route for through traffic. But a second deck on I-285 could let the drivers in high-occupancy lanes on or off at multiple points, Jordan said.

The state is also examining how to pay for the overhaul of I-285's top end, whatever form it takes.

Federal dollars should be available under the Atlanta Regional Commission's 25-year funding plan, said Jane Hayse, the ARC's transportation planning chief. She noted that the ARC in 2003 studied building either two high-occupancy-vehicle lanes or two bus rapid transit lanes above the section of I-285 in question.

Some of the money may come from the private sector, though only if investors believe the tolled lanes will generate enough to repay them.

On a related note, the companies behind Georgia's first public-private highway deal (including PBS&J), the $2 billion expansion of I-75 to 23 lanes in Cobb County, are looking at building elevated lanes in at least one section to avoid destroying office buildings on that corridor.

How it might look

If elevated lanes are built on I-285, they would probably bear some resemblance to three new toll lanes being built above the median of an existing four-lane expressway from downtown Tampa to its eastern suburbs.

Unlike the I-285 idea, the lanes in Tampa are reversible, carrying traffic into the city in the morning and out at night along a six-mile stretch without exits or entrances. The road was budgeted at $370 million but collapsed while under construction in 2004, due to what the Tampa-Hillsborough County Expressway Authority said was a flawed foundation design, forcing $120 million in repairs.

It is expected to open in August, but expressway interim executive director Ralph Mervine said a portion that opened in November is already cutting 10 minutes or more off average commuting times, and will be cheaper for the city in the long term over adding more lanes on the ground.

Atlanta's clogged interstates are perfect for double-decking, said Linda Figg, president of Figg Engineering Group in Tallahassee, Fla., which designed the elevated lanes in Tampa (but not the foundation) and San Antonio, and is studying the prospects for Birmingham.

"It creates an express lane scenario for whatever kind of traffic you put on it," Figg said.

Elevating lanes means there are fewer to cross in order to reach the fast lane or to exit, and ensures drivers using them will not be affected by accidents below.

On the other hand, putting them in place means traffic will suffer more disruption during construction than with surface lanes, and their appearance can be unsightly, said Michael Meyer, a Georgia Tech transportation expert.

Mike Kenn, president of lobbying group Georgians for Better Transportation, said he is glad the state is considering double-decking part of I-285.

"I believe that's the appropriate direction they need to go."

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