Signalized Intersections—Planning Methodology

The first appearance of a formal planning methodology for signalized intersections appears in the 1985 Highway Capacity Manual (Highway Capacity Manual in Special report 209. Transportation Research Board, Washington D.C. 1985, [1]). It was introduced because in 1985, doing a quick hand-computed assessment of a signalized intersection became extremely difficult and time-consuming. By 2000 and beyond, it became virtually impossible. The model for the initial planning approach became the signalized intersection methodology introduced in TRB Circular 212 in 1980 (Interim Materials on Highway Capacity in Circular 212. Transportation Research Board, Washington D.C., 1980, [2]). To this day, there are some agencies that continue to use the Circular 212 methodology because of its simplicity and ease of use.