Are the ITE formulas the only “engineering practices” that can be used to determine duration of yellow change and red clearance intervals?
No, the MUTCD just lists the ITE publications as examples of engineering practices for these determinations. However, the FHWA suggests that the ITE guidelines be used as a starting point, because those ITE guidelines utilize scientifically derived formulas based on engineering principles and years of research. The yellow change interval is calculated based on speed of approaching vehicles, the stopping ability of approaching vehicles, and the width of the intersection. Significant safety benefits have been found to result when yellow change intervals are retimed using the ITE guidelines.
