Because a majority of visitors to Knoxville are thru travellers to Great Smoky Mountains National Park, many travel by car. The downtown area caters to such visitors with a number of free or reduced price parking areas for the specific use of visitors to the city. In addition, most attractions located downtown can be reached by either walking or taking the free trolley service. The trolley service also runs late at night on Friday and Saturday evenings, to provide you a safe alternative for travel when hitting up the downtown bar and restaurant scene. Because public transportation is limited, if you wish to visit sites outside of the city such as Oak Ridge National Laboratory, you will need to have access to a car.