One of Ottawa's LRT trains is getting a special set of axles as OC Transpo launches testing that could put more double-car trains on the rails next year.

The new axles are retrofitted with pins to hold a restraining nut in place. That problem nut has been coming loose, and train manufacturer Alstom blames it for bearing issues that have caused derailments.

Richard Holder, the city's director of engineering services, said the axles have arrived in Canada and are being fitted onto one train.

"If testing is successful, it may allow for an increase in double-car trains and allow for an increase in the passenger capacity of Line 1," he told councillors on Thursday, referring to the east-west Confederation Line.

The train won't carry passengers during testing, Holder said.

The city's general manager of transit services Renée Amilcar said testing is scheduled to begin next week. The special train will have to run 1,500 kilometres, and it will take time to strip down the hub assemblies, take measurements, analyze the data and look for anomalies.

"We should be able to have good news at the beginning of next year," said Amilcar. That "good news" means more double-car trains, she confirmed.

OC Transpo has been holding back cars to avoid wear and tear. Right now, the axles have to be replaced every 60,000 kilometres, and Holder has worried supplies will run out.

He hopes the new pin will significantly extend their lifespan.

"We will burn through a lot of axle hubs based on that 60,000-kilometre replacement," Holder said. "The nut-pinning solution will allow the range on those hubs to be greatly increased, so what we are expecting through the nut-pinning solution is that we will eliminate that supply chain issue."

Stittsville Coun. Glen Gower, who chairs the city's transit commission, said those comments left him feeling "confident." He said he's seeing an increased need for double-car trains.

"It's important because we are seeing increased ridership, and we need to be able to ensure that we have the capacity to provide that for our passengers in the months ahead," Gower said.

Under the LRT project agreement, there are supposed to be 34 light rail vehicles, enough to run 15 double-car trains while keeping four cars back as spares.

OC Transpo said Thursday there are currently 19 cars on the line during the week, running as six double-car trains and seven single-car trains.

During the weekend, there are seven single-car trains and no double-car trains, they said.