O-Train running at reduced speeds during hot and humid weather

Ottawa's light-rail transit system is operating at reduced speeds this week due to the hot and humid weather conditions.

OC Transpo says Confederation Line trains will operate at a maximum speed of 50 kilometres per hour on above ground sections of the track until temperatures drop below 30 C.

"Customers may experience a slight increase in travel time of up to a few minutes as a result," OC Transpo said in a statement to CTV News Ottawa Wednesday night.

"This operating procedure is implemented whenever temperatures are above 30 degrees Celsius. OC Transpo is always monitoring weather conditions and is prepared to adjust service depending on the severity of the forecast."

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Ottawa has seen temperatures hit 30 C for three straight days, including 33.7 C on Wednesday.  Environment Canada's forecast calls for a high of 32 C on Thursday, before daytime highs drop to 27 C on Friday and 25 C this weekend.

The transit service says the city and Rideau Transit Group take a number of steps to "continue to safely operate the O-Train" during the hot and humid weather, including:

• Train operators carefully observe the track and keep the Transit Operations Control Centre (TOCC) informed of operating conditions
• Maintenance staff increase inspections throughout the day and night
• Temporary Speed Restrictions (TSRs) may be put in place on above ground sections of track

The maximum speed on the Confederation Line is 80 km/h.

A "Sun Kink"

OC Transpo says when temperatures get hot, the steel tracks can expand and shift to cause a "sun kink."

In a video posted on social media, the transit service says a "sun kink" happens on rail systems around the world.

"When the temperature gets extremely hot and the sun is beaming down, the steel tracks can expand and cause buckles," OC Transpo says. "If a track gets a sun kink, it can bend the track slightly out of alignment and can cause problems for trains trying to pass by."

"When they expand to a point that creates additional stress on the rail and it actually can bend the rail slightly and customers would feel that on the on the train," said director of rail operations Troy Charter. "So, in order to make sure that our trains continue to run safely and reliably in these extreme heat situations, we implement temporary speed restrictions."

Charter said this is a regular occurance on rail lines.

"Any rail property that deals with extreme heat situations would that would have similar processes and procedures in place," he said.

"When the temperature drops below 30 degrees, we're able to lift those temporary speed restrictions."

OC Transpo adds the slower train speeds during hot and humid days "reduces the impact on trains and helps decrease the changes of sun kicks expanding and becoming worse."