Waltham will begin operating a free trolley Thursday, June 18, to shuttle downtown visitors between parking lots and popular destinations along the Moody Street corridor, according to Mayor Jeannette McCarthy’s office. The “Tick Tock Trolley” will run in a loop on Thursdays, Fridays, and Saturdays from 6 to 11 p.m., starting on Lexington Street near the Waltham Museum and winding through downtown on Moody before circling back near Orange Street and returning to the Common Street garage, with multiple stops along the way. The route may be adjusted after the service begins. The shuttle will help the city manage its parking spaces in 11 downtown areas, according to the mayor, and better serve local businesses, residents, and visitors. For more information, including a map and a list of stops along the initial route, check the City News links at www.city.waltham.ma.us.