PREDICTION OF THE SERVICE LIFE OF WARNING SIGNS.

A key decision facing highway maintenance administrators is when to replace retroreflectorized signs installed on streets and highways. The real problem is identifying signs which need to be replaced due to loss of retroreflectivity. The retroreflectivity service life (RSL) model was developed to predict when a sign has reached the end of its useful life. The model is based on providing drivers with the minimum visibility distance required for safe and efficient response to the sign message. A microcomputer program has been developed to simplify the use of the retroreflectivity service life model. This program computes the minimum required visibility distance and the minimum required SIA values, and - based on user-supplied inputs - predicts the month of replacement for 30-inch (762 mm) symbol warning signs.