PORTLAND — Traffic is expected to be heavy on the Maine Turnpike over Columbus Day weekend, marking the unofficial end to Maine’s tourism season.

Most people are surprised when they learn that the Columbus Day holiday weekend is the second-busiest weekend of the year on the turnpike, behind Labor Day weekend, said Maine Turnpike Authority spokesman Dan Morin.

The highway had more than 950,000 toll transactions during the Friday-through-Monday weekend in 2010 and 2011, and about 922,000 last year, when the weather wasn’t so good. By comparison, there were 971,000 toll transactions on Labor Day weekend this year.

“It’s surprising to see how similar those numbers are,” Morin said.

In 2012, Thanksgiving weekend was the third-busiest travel weekend of the year on the turnpike, Morin said.

The first and second weekends in August are usually in the top five busy weekends, he said.

About 60 million vehicles travel on the turnpike each year.