Heavy trucks are scraping the top of a newly renovated train viaduct on Marcel-Laurin Boulevard, contributing to delays on the problem-plagued Deux-Montagnes commuter rail line.

Since November, at least seven trucks have hit the ceiling of the underpass in Saint-Laurent, according to a report by Radio-Canada.

Each time this happens, train service is halted for the 31,000 daily passengers who use the nearby Bois-Franc train station.

"As soon as someone reports that they collided with this viaduct, we have to make the necessary inspections," said Caroline-Julie Fortin, a spokesperson for the Réseau de transport métropolitain, the agency that operates the Deux-Montagnes line.

A solution, she said, is required urgently.

Passenger frustration is already high with the service on the Deux-Montagnes line. Delays have accumulated in recent months, which the RTM has blamed on a number of other factors, including snow, freight-train traffic and problems with the signalling system.

See and hear what happens when a truck goes under a viaduct and scrapes the ceiling by watching the video below.

See and hear what happens when a truck goes under a viaduct and scrapes the ceiling. 0:26

Truckers must respect height limit: city

The issues with the viaduct on Marcel-Laurin Boulevard emerged following city repairs to the road beneath. Before that, ruts had emerged that provided just enough space for trucks to pass through.

"Now that we have corrected the asphalt problem, the surface is smooth and straight, and unfortunately, there may be a few millimetres less space for trucks to cross through the tunnel," said city spokesperson Philippe Sabourin.

A sign on the viaduct indicates that trucks exceeding a maximum height of 3.95 metres are not allowed to pass through. The viaduct actually measures 3.99 metres — four centimetres more. The city has no plans to redo the road work.

"The City of Montreal has respected the permitted height," Sabourin said. "Now, it's up to the truckers to change their habits, and respect the signage."