GO customers may be eligible for refunds if their train is more than 20 minutes late. (Canadian Press )

Starting this fall, commuters in the Greater Toronto Area will be able to get their money back if their GO Transit train is more than 15 minutes late "except when delays are caused by extreme weather, police investigations, accidents and medical emergencies."

The Ontario government says the service guarantee will affect all GO train commuters.

Premier Dalton McGuinty floated the idea of a GO train guarantee last June before the fall election campaign.

At the time, he said the proposed refund system would likely cost between $6 million and $7 million.

Progressive Conservative Leader Tim Hudak dismissed the GO train guarantee as a gimmick.

He says it's more important to make sure the trains pull into the stations on time.

The province says GO Transit, which moves about 62 million passengers annually, has maintained a 95 per cent on-time rate for its trains over the past year.

"For the last 45 years, GO Transit has provided commuters in the Greater Toronto and Hamilton Area with safe, reliable public transit," said Bob Chiarelli, minister of transportation and infrastructure.