THE HIGHWAY CAPACITY MANUAL DELAY FORMULA FOR SIGNALIZED INTERSECTIONS

This article, which compares the 1985 U.S. Highway Capacity Manual delay formula for signalized intersections with Australian and Canadian formulas, also presents a generalized form that incorporates them all. An alternative to the HCM delay formula, which matches the other formulas for oversaturated conditions, is given. The alternative formula derived from the generalized formula, predicts delays that are very close to those predicted by the original HCM formula for undersaturated conditions, and at the same time predicts delays that are very close to the results from the Australian and Canadian formulas for oversaturated conditions. The generalized formula could be calibrated to develop a more suitable formula for U.S. conditions. It might also be possible to calibrate it for vehicle-actuated and fixed-time signals separately.