Better Roads Staff
Both Ends to the Middle
It’s not either end of this bridge that is its most important entrance/exit point. It’s the middle.
That situation occurs because when you contract to add lanes to a divided Interstate using the median for the new roadway, you have a number of problems to solve, but one really, really big one. Access. But if you think innovatingly, let’s say daringly, enough, you don’t have do the work predictably.
The I-85 widening project in Cabarrus County, N.C., involves the widening of approximately 8 miles of aging and deteriorated Interstate with complete replacement of all pavement and six bridges. The job was design-build and contractor Lane Construction came up with an out of the box, stunningly simple and innovative temporary bridge – with median access ramps – concept.
“The majority of the new roadway width is being constructed in the existing 70-foot median, creating a very difficult access challenge and potentially severe safety concerns for the traveling public,” says a Lane spokesperson. “These challenges are typical on Interstate widening projects yet they are always difficult to overcome. The need for an innovative work zone traffic control and access plan is particularly critical on this design-build project due to the severe state of deterioration and Average Daily Traffic of over 100,000.
“Unimpeded access to the existing median is critical to improve safety, minimize impacts to traffic, reduce stress on existing peripheral infrastructure, accelerate the project schedule, and reduce cost of construction by increasing efficiency.”
NCDOT resident engineer Davis Diggs says the bridge wasn’t in the RFP but Lane delivered a technical proposal to access the median via a temporary bridge with access ramps. The spec’d out proposal was presented to NCDOT and went through the usual review process. And NCDOT had to review and approve not only the bridge’s construction but also its later disassembly and removal.
The temporary access bridge snapped up the attention of Federal Highway Administrator Victor Mendez who visited the project. Mendez has constantly urged more innovations and creativity to reduce delivery time and add value to transportation infrastructure projects.
“The flexibility for all the experts to come together and put together the solutions that are needed like this temporary work bridge, and separating the traffic and the general public, is very, very creative.” Mendez told local television station WBTV during that visit.
While the bridge was an unexpected move Diggs says NCDOT and Lane worked seamlessly to make it work.
“The project originally had some pretty restrictive time constraints for median access,” says Diggs. “Lane’s bridge allowed them to do a lot of things, including working during the day when restrictions would have limited them. Without the bridge there would have been more night work because of the daytime restriction, and night work is more dangerous.” And of course, says Diggs, it can be more expensive.
With the bridge Lane could work at night without interacting with traffic.
The safety improvements resulting from this concept are significant. The need to haul loads of material across major feeder road and interstate traffic into the median has been completely eliminated. Thousands of trips by construction and NCDOT inspection staff have also been made safely and without entering traffic, says Lane’s spokesperson.
The temporary bridge and its access ramps allowed Lane to make a bid with a more aggressive schedule that NCDOT had expected. The project, begun in 2011, will be done in 2014.
The problem of course is the work zone. There is traffic to deal with, the safety of workers, and the development of a schedule for equipment and material supply (40,000 loads of material had to cross the interstate to reach the median) and the need for personal from both Lane and NCDOT to come and go. And a backup plan when something goes awry. In this case two factors stood out beyond the predictable: The existing roadway badly deteriorated and there was an average daily traffic flow of more than 100,000 vehicles.
Lane looked for an existing bridge as a jumping off point in this project, but the traffic load and contract hauling restrictions meant no go. This is the point where innovative thinking stepped in. And, says Lane, as far as they know this is the first median access ramp off a temporary bridge.
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