The spacing of driveways and streets is an important element in roadway planning, design, and operation. Access points are the main source of accidents and congestion. Their location and spacing affects the safety and functional integrity of streets and highways. Too many closely-spaced street and driveway intersections increase accident potential and delays, while too few inhibit access and over-concentrate traffic. More than 40 years of research has indicated that accident rates increase with the number of intersecting roadways or driveways per mile. As early as 1953, research results showed that accident rates generally increased with both the frequency of access and the average daily traffic; however, the greatest increases resulted from increasing the number of access points per mile. More recent studies in Oregon, Florida, Colorado, and elsewhere found similar relationships. The consistent pattern of the research results from the above and numerous other studies is clear; the greater the frequency of driveways and streets, the greater the rate of traffic accidents. Increasing the spacing and providing a greater separation of conflict points reduce the number and variety of events to which drivers must respond. This translates into fewer accidents, travel time savings, and preservation of capacity. (A)
Abstract