Construction delays precipitated by June's sinkhole on Rideau Street have prompted the City of Ottawa to shut down a busy stretch of the road to all vehicular traffic so crews scrambling to complete the light rail tunnel underneath can work around the clock.

The closure, from Sussex Drive to Dalhousie Street, will go into effect at 8 p.m. Wednesday and will remain in effect until the end of December, the city said. Buses will be re-routed, and taxis and deliveries will be forced to steer clear of the area.

Rideau Transit Group, the construction consortium building the Confederation Line, needs to inject grout-like material into the ground to stabilize the area surrounding the concrete that was poured into the crevasse caused by the sinkhole before workers can complete the final 35 metres of the 2.5-kilometre tunnel.

"They were delayed in that area because of the sinkhole under Rideau," said Steve Cripps, director of O-Train construction of RTG. "They're behind where they wanted to be on this."

RTG wanted 24/7 closure from outset

Cripps said RTG always wanted Rideau closed around the clock, but the city asked the consortium to try working from 8 p.m to 6 a.m. instead.

"They tried overnight only, but the production rate was not what they needed it to be to remain on schedule."

RTG would be on the hook for costly penalties if it does not complete the LRT by spring of 2018.

Cripps said working around the clock will also let crews avoid winter weather as much as possible.

The final decision to close the road to traffic was made in the last few days, so businesses along Rideau had little notice of the impending road closure.

Sidewalks will remain open to pedestrians, but the 350-metre stretch of road near Rideau Centre will be off-limits to buses, taxis and delivery trucks for more than two months.

That section has been restricted to those vehicles for more than a year due to construction, and overnight detours have recently been in place.

OC Transpo has made the following changes because of the closure:

Routes 1 and 7 will operate via Daly Avenue and will stop at the intersections of Rideau and Dalhousie streets, and Daly and Nicholas Street.

Routes 2 and 4 will operate along Albert and Slater streets, ending at the corner of Elgin and Sparks streets.

Route 9 will start at Rideau and Sussex and end at Rideau and Dalhousie.

Routes 12 and 18 will stop at Rideau and Dalhousie and will end at Daly and Nicholas. That intersection will become the starting point for eastbound trips.

Route 14 will run on the Mackenzie King Bridge.

Free OC Transpo buses will run from 10 p.m. to 3 a.m. Thursday, Friday and Saturday nights from the ByWard Market to the Mackenzie King Bridge, where passengers can transfer to Transitway routes.

This closure is similar to the road closures put in place as construction crews worked to repair a large sinkhole on Rideau near Sussex in June.

The Confederation Line is due to be finished in 2018, in the city has said the project remains on time and on budget.