Flooding forced the closure of a Highway 40 exit ramp Sunday night, and some drivers had to be rescued by emergency services after close to 25 millimetres of rain fell on the Montreal area in about two hours.

About six cars were caught in the flooding at L'Acadie Circle, an underpass on one of the city's busiest highways that was renovated as recently as 2005, but continues to create problems.

It's the second time the underpass has been flooded this month alone.

Saeed Mirza, a McGill University civil engineering professor, said Monday the underpass was poorly planned.

"Somebody must have missed out on how much water could accumulate here. The area lies in a little valley," Mirza said.

He said the city should install a storm drain, because the frequent floods are creating additional wear, and could shorten the road's lifespan.

"It becomes a safety issue. Do we wait till we get an accident? We shouldn't," Mirza said.

No one from the city was available for comment Monday.