Troublesome LRT restraining rails are on the move. What are they?

Work has begun to move the safety rails that guard against derailments along Ottawa's light rail transit line, according to OC Transpo.

The rails will move just one or two millimetres, a shift the light-rail transit system's builder and maintainer say should help ensure the heavy metal bars no longer damage parts of the train. 

The move is yet another measure to mitigate against the risk of another system failure until a permanent fix is ready — and a necessary fix before service can relaunch. 

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Restraining rails are a fixture on all sorts of rail infrastructure, and experts say the consistent contact that Rideau Transit Maintenance has been observing between the rails and the train wheels is not meant to happen. 

The issue is related to problems that caused the most recent damage to a bearing, and two earlier derailments.

What is a restraining rail? 

Richard Holder, the city of Ottawa's director of engineering services, calls the rails a "passive safety device" located within curves. They run parallel to the rail at a distance of about two inches. 

"The only times that we would expect contact [between the rail and the back of the wheel] would be if there was a risk of derailment," he told reporters earlier this week. 

"If a train, for whatever reason, was travelling around a corner and the outside wheels started to climb the outside rail, at that point there would be in contact with a restraining rail and a derailment would be prevented." 

That climbing happens because of the force exerted on a train as it rounds a curve at high speed. 

Renée Amilcar, the general manager for transit services, likens it to a driver accelerating a car around the corner and unbalancing the vehicle to the point that two of its wheels lift off the road. 

"It's normal with your car," she said to media. "We want all the wheels to be on the rail ... the restraining rail will force the high rail, as we call it, to stay on the rail."

WATCH | This is what Ottawa's restraining rails look like

What is a restraining rail and what does it look like?

1 year ago

Duration 0:40

Ottawa officials and LRT stakeholders are looking into concerns with the train system's restraining rails. These rails have been doing something experts agree they should not: consistently rubbing against wheels.

Why are Ottawa's restraining rails a problem? 

The problem with Ottawa's restraining rails is related to a broader issue with the system that has been widely reported on for years: tight curves in the system's east end. 

The city highlighted eight problematic areas, particularly those located near Hurdman station. 

Some of these curves were identified by Mott MacDonald, a British firm hired by the city of Ottawa, as areas that have suffered from wheel corrugation — "a periodic wear of the rail surface into peaks and troughs" — and rolling contact fatigue, where the rail head becomes cracked due to "contact forces between the wheel and the rail."

Little or no corrugation was found in areas with straight track or shallow curves. 

The 2022 report warned of premature deterioration of the light-rail vehicles and "increased maintenance."

Last year's public inquiry into various issues with the rail system also identified concerns over the "rail inclination" or degree of sloping at the curves. 

When asked about that issue on Thursday, Holder said there's "no risk of derailment" because of the current wheel-rail interface.  

Why wasn't this contact issue identified before? 

Contact with the restraining rail has been a known issue for a while, but was only identified as a pressing concern in a recent safety note from trainmaker Alstom and system builder Rideau Transit Group.

The city and RTG have said the issue is not a design defect, but a problem with maintenance. 

"That is mainly due to the fact that we've been running the system for three years and all systems go through a process of wear, both of the wheels and of the rails," said Holder. "We're currently dealing with that new situation."

Nicholas Truchon, RTG's chief executive officer, said this will not become a recurring issue, because the last two weeks has helped "clarify" parameters that will allow maintenance crews to more effectively make adjustments. 

Why will it take ten days to move them?

The restraining rails are now being moved by a millimetre or two, a process that's set to take a full ten days.

That means teams will need to begin testing trains before work on the rails has been completed, if the city wants to meet its goal of reopening the Confederation Line to passengers on August 14. 

"It's true that it seems relatively easy to move something one or two millimetres," said Enrique Martinez Asensio, RTM general manager. "But the reality is that the restraining rail is a very heavy steel profile that is bolted to the frame components of the track." 

Specialized machines are required and crews need to be trained, he said. 

"It's just a few millimetres, but we are talking about a lot of work."