Rebuilding a rollover-prone intersection on the South Fraser Perimeter Road in Delta with an overpass would be a costly last resort only if other options fail to improve traffic safety there, according to an independent review released by the transportation ministry.
Delta Police last year flagged the Highway 17 intersection with Highway 91 Connector as a hazard, describing the downhill grade and banked curve as a tricky "twist" that may have contributed to five rollover truck accidents there in 2014.
The province commissioned a design review by consultants R. F. Binnie and Associates, who found there's little that can be easily done to reduce the probability of crashes besides getting trucks to slow down.
Because of the design, it said, trucks coming downhill on Highway 17 to turn left onto the connector risk overturning if they're going more than 26 kilometres an hour.
"The ultimate long term solution would be to replace the intersection with a grade-separated facility," the report says. "This is a very costly solution and construction of an interchange would only be considered if the preceding recommendations are not effective."
The transportation ministry already put up signs warning of the truck rollover risk and posted a 20 km/h advisory speed limit on two of the intersection approaches. No more trucks have rolled since that signage went up last fall.
That could be supplemented if necessary with electronic or flashing speed warning signs, the report said.
The review found the design of the intersection is "generally compliant" with established engineering guidelines, although the four per cent grade is steeper than the maximum desirable grade of three per cent.
Excessive speed is the main factor in truck rollovers, it said, particularly as trucks turn from the 80-kilometre-an-hour SFPR (Highway 17) to the 60-kilometre-an-hour Highway 91 Connector.
Delta Police Acting Sgt. Sarah Swallow said slowing to 20 km/h to make the turn safely is a challenge for truckers approaching the intersection on a green light.
"Slow down and then slow down some more," she advised, adding trucks' loads can shift and cause them to flip if a driver brakes too fast.
The $1.26-billion South Fraser Perimeter Road was opened in 2012 as Highway 17.
The Highway 91 Connector intersection is one of three intersections that the province opted to build on the SFPR with traffic lights rather than on- and off-ramps as a cost-saving measure, despite predictions that making trucks stop at red lights would slow traffic on the route.
"It's too bad that interchange was not built when the road was built," Delta Mayor Lois Jackson said. "It will have to be done eventually. It's just a question of when."
Intersection of South Fraser Perimeter Road and Highway 91 Connector. Evan Seal / Surrey Leader