29 hour closure of Dallas North Tollway for new bridge girder lift

Several miles of the southern end of the Dallas North Tollway (DNT) will be closed this weekend starting just before midnight Saturday night through all of Sunday and until 5am Monday morning. Contractors for the North Texas Tollway Authority will swing in beams for a new longer Cedar Springs Road Bridge they are building just north of the Wycliff Toll Plaza (#1).

The 29 hour closure will also transition work on the roadways to reroute traffic onto new pavement. 40 year old pavement is being fully replaced for the first time.

This south end of the DNT, and the oldest part, has about $50m of reconstruction going on. About $34m is being spent on the mainline on either side of and through the toll plaza with rebuilding of the pavement, addition of shoulderspace and a 4th auxiliary lane.

New access/egress

Another $16m (some of it from the city and TxDOT) on ramps to Oak Lawn Avenue, a cross street near the southern end of the tollroad, plus widening of the avenue on either side, will provide a new way on and off the DNT at its southern end.

The Cedar Springs Road bridge getting new girders this weekend is being lengthened. That was originally intended to provide a more gentle merge area going north out of the toll plaza. However NTTA decided in the spring -midway through the southend project - to phase out cash toll collection. A contract had been awarded for 12 new cash collection lanes in place of 15 there previously, but work on that has been frozen. Design work had been done on a grand new canopy and bids advertised but fortunately no contracts had been let.

Redundant buildings

Mark Bouma engineering director says there is some work already done on the toll plaza that won't now be needed, but not a great deal. The most prominent piece of construction likely to prove redundant under full electronic tolling is a toll operations building - about half built, and construction now halted. Without toll collectors and cash to handle the building won't be needed, at not least for its previously planned function.

The NTTA has a group looking at what it can do with land and buidlings made redundant by the phase-out of cash collection. Around the old toll plazas close to the city the land could fetch a high price.

Bouma says the bridge lengthening won't be a loss because the NTTA needs it to accommodate 4th lanes all the way up to the next interchange ramps - an auxiliary lane - which will improve traffic flow. The old bridge would only accommodate 3+3 travel lanes. It is a skewed bridge so the new bridge has a long span - about 150ft (46m).

It isn't clear if the auxiliary lane each direction will be carried under the new mainline electronic toll gantry though a merge before a toll point seems problematic. We'll post on that when we get clarification.

Still to do - new ramps to I-35E

Major work needed at the south end still is wider ramps DNT to I-35E. The present single lane ramps are a bottleneck.

That project has to wait on TxDOT reconstructing I-35E. New two lane ramps will land at a different point on the rebuilt freeway. So it makes sense to stage that in conjunction with the TxDOT's work which is a couple of years away.

BACKGROUND: The DNT is 22 miles (36km) long and of 3+3 lanes and it heads due north out of the center of Dallas. Its first segment opened in 1968 and it is being extended steadily north... toward the Oklahoma state line.

The tollroad has had open road or highway speed electronic tolling through the center of the toll plazas - mostly in 2+2 lanes - for about five years.

TOLLROADSnews 2007-07-24