"We have as of today now signed the final contract to complete the twinning of Highway 63," Prentice told an audience in the oilsands city.
He said 22 per cent of the 240-kilometre stretch of road is twinned. That figure will go up to 78 per cent by next year with completion the year after that.
"The entirety of the twinning of Highway 63 will be completed on time and on budget as originally promised."
The province will spend $423 million this year on the project - about double what it spent last year.
The highway is the main road to Fort McMurray and has become overloaded in the last decade as work in the region skyrocketed.
The road has been the site of frequent traffic snarls due to slow-moving oversized trucks. It is also known for multiple head-on crashes, cars hitting the ditch, high-speed tailgating and drivers going at dangerous speeds of 160 km/h or higher.
Critics have said that while twinning will cut down on head-on crashes, authorities must continue to crack down on speeders and dangerous driving.
For six years, the Progressive Conservative government did little to fulfil its promise to twin the road. That changed in the spring of 2012 when a head-on crash killed seven people and galvanized the public to demand action.
Then-premier Alison Redford's government took on debt to pay for construction and set a goal of 2016 for completion.
Redford quit politics this year after revelations surfaced she had abused the public purse through extravagant spending on herself, her travel, her office and inner circle.
In the campaign to become PC party leader and premier, Prentice promised to clean up the excesses of the Redford era. He has since committed to sell the government air fleet and promised new laws to prevent cronyism and entitlement.
Redford has kept a low profile since her departure from caucus in August and does not appear at party events. PC members rarely, if ever, mention her by name in public.
On Thursday, Prentice reminded Albertans that the government had kept its promise about twinning Highway 63, but did not mention Redford or her contribution.
Opposition Wildrose critic Rob Anderson said the issue goes further back than Redford. He also criticized Prentice for making the announcement while running in an Oct. 27 byelection in Calgary-Foothills.
"Redford was responding to pressure from the Opposition (when she) promised to twin 63 — and so Prentice spends govt money to take the credit? No shame," wrote Anderson on Twitter.
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