Several factors affect the design of parking facilities, particularly at entry and exit points. These factors include pedestrians, traffic control, turning restrictions, on-site circulation patterns, site distance, topography, and traffic volumes.
Try to keep entry or exit points away from intersections--a 200 foot or greater 'throat length' is desirable, particularly at a larger facility such as a PX or Commissary. Ensuring safe entry into the site is important. A short throat length leaves little room for vehicles to stack when presented with an internal conflict, and it also results in insufficient reaction time to the conflicts that a driver will encounter upon entering the site. Crash potential is increased significantly with this scenario.
A minimum driveway radius return of 20 feet is recommended. A 25-foot minimum throat length is required for the actual driveway per UFC 3-210-02. A driveway width of 25 feet is recommended for two-way traffic flow. A qualified engineer should determine the exact spacing and location of access points.
In accordance with UFC 3-210-02, provide more than one entrance and exit for parking lots with more than 100 parking spaces.