ADA accessibility guidelines specify the number and dimensions of accessible parking spaces required at buildings and facilities. The number of accessible spaces is determined by the total number of parking spaces: 1-25 spaces require 1 accessible space; 26-50 spaces require 2 accessible spaces; 51-75 spaces require 3 spaces. For larger facilities, one additional accessible space is required for every 75 additional total spaces. Van-accessible spaces must comprise at least one of every six accessible spaces. Standard accessible parking spaces must be minimum 96 inches (8 feet) wide, with an additional 60-inch minimum (5-foot) width access aisle. Van-accessible spaces must be 132 inches (11 feet) wide with 96-inch access aisle. Accessible parking spaces must be located at the accessible entrance to the building with maximum 200 feet distance. Spaces at entrances requiring longer travel may be supplemented with additional spaces closer to secondary entrances. Surface slopes may not exceed 1:48 (2.08 percent) in any direction. Access aisles must be at the same level as the parking space with no raised curbs, and must extend the full length of the space. Accessible spaces must be clearly marked with the wheelchair symbol on the pavement and with a vertical sign. The sign must be 60 inches minimum above the ground and visible from vehicular approach. Van-accessible signs must include the van symbol.