Work begins on 'diamond' interchange at I-40, Highway 66

Apr. 05, 2014 @ 11:01 PM

Modifications to the Exit 407 interchange are supposed to make the county’s only Interstate junction more efficient. In the meantime, though, the work will likely add to weekend backups as it shifts traffic into new configurations during construction.

The Tennessee Department of Transportation says the new design, called a “diverging diamond” or a “double crossover diamond,” will help traffic more easily flow from Highway 66 onto Interstate 40 and vice versa.

“The Diverging Diamond interchange at I-40 Exit 407 will help get motorists to and from the (Sevier County) area in a safer and more efficient manner,” TDOT spokesman Mark Nagi said.

The redesign calls for the northbound and southbound lanes of Highway 66 to switch to opposite sides of the highway just before they reach the bridges over the Interstate. TDOT officials say the new design will improve traffic flow because drivers won’t have to turn left across oncoming traffic. It also calls for improvements to the Interstate, including a lengthened and widened ramp for people getting off I-40 eastbound. J&M Construction Grading Divison won the contract. The projected completion date for the $15.6 million project is May 15, 2015.

The first phase of the project includes construction of new on and off ramps. The contractor has started work on Intersate 40, forcing Interstate traffic toward the median as it approaches the interchange in both directions.

That has added to backups as traffic adjusts to the new configuration, especially on Fridays, as tourists use the county’s only Interstate access to visit for the weekend.

It’s not clear yet how long that work will last. “TDOT is working with the contractor concerning time constraints placed on each phase of work,” Nagi said. “Those time frames are not set yet.”

For now, the construction is mostly along the eastbound Interstate ramps. That will change sometime in the coming weeks, as the contractor starts working on the parallel bridges and the medians on either end of the bridges, where the crossovers will be implemented.

“Construction of the median area where the crossovers are, will happen mostly in Phase 1,” Nagi explained. “Phase 1 consists of sub-phases. In the first sub-phase we will construct temporary lanes in the ‘crossover’ areas...At this time, through traffic will be on the outside lanes going across the bridge. After traffic is temporarily switched across the ‘crossover’ areas, the contractor can start work on the outside lanes on the roadway and across the bridge.”

The traffic wont’ be “crisscrossing” at that point, he said. It will be moved to the inside lanes as it crosses the bridge.

Phase 2 will include moving traffic onto the new ramps and installation of poles for new traffic lights, as well as work in the median south of the interchange.

The final phase of the project will require the placement of new traffic signals, as well as finally shifting traffic on the highway. It will require closing the interchange overnight sometime near the end of the project, Nagi said.

“The detours in Phase 3 should be done in one night during the end of the phase,” he said. “This detour will happen so that the contractor and his subcontractors can remove temporary traffic control devices and temporary striping patterns so that the final pattern and traffic placement can be implemented.”