BELFAST, Maine — Thousands of cyclists and their supporters will be in Belfast this Sunday as the annual Trek Across Maine comes to a close, and local police are urging drivers to be patient and careful as they travel through the city.

“We ask that people pay attention to the cyclists,” Belfast police Chief Mike McFadden said Friday. “This is the last leg of a fairly long trek. There’s going to be a lot of people, a lot of cars, a lot of bicycles, a lot of pedestrians. We just ask people to be patient. This will be an extremely busy weekend, but we’ll get through it.”

The Trek Across Maine is a three-day, 180-mile cycling event that started Friday in the mountains of Sunday River and ends at the sea in Belfast on Sunday. It is the largest fundraising event of its kind in the country for the American Lung Association. To date, the event has raised more than $22 million in the past 30 years. On Friday, riders will stop overnight at the University of Maine at Farmington and then continue Saturday to the Colby College campus in Waterville.

In Belfast, where the trek concludes on Belfast Common overlooking the harbor, the riders will be cheered on by many onlookers as they finish their long ride. They will enter the city on Route 3, with the first cyclists coming in at about 9 a.m. and the bulk of them arriving around noon. According to McFadden, the riders will turn right off Route 3 and peddle through the athenahealth office complex, then turn back onto Belmont Avenue close to the Reny’s Plaza intersection. From there, the riders will pedal into town via Alto Street and then Miller Street.

This year, the city will stop vehicles from driving onto Belmont Avenue from Starrett Drive, where the Hannaford Supermarket and other businesses are located.

“Over the years that we’ve had this particular route, we’ve noticed that Starrett Drive and Belmont Avenue is a particularly difficult intersection,” McFadden said. “In years past, we’ve had issues having the traffic back up onto the intersection of the Route 1 overpass, and we don’t want to see any accidents happen as a result of that. This will be the only road closure as a result of the Trek Across Maine.”

In addition to the thousands of cyclists who will arrive Sunday, Belfast also is gearing up for a different sort of event Saturday, when the Bangor-based Anah Shriners and the Lewiston-based Kora Shriners will come to town for a joint parade that will begin at 2 p.m. The parade will be staged near Belfast Area High School and travel on John Street to get to High Street, where it will proceed all the way to Belfast City Park.

“I have been told by officials organizing this that it’s a very large parade,” McFadden said. “There’s going to be a lot of units in this parade — everything that you might expect from a Shriners parade times two. It’s going to be huge, and it’s going to be busy.”