The purpose of this research is to add new insights regarding the benefits and drawbacks of using intersections with three-phase traffic signals compared to other intersection designs and to develop a technical guideline to help designers and policymakers in transportation understand when and where to use three-phase designs.
This study seeks to answer the following questions: (1) At what locations are three-phase designs most well suited? (2) How much do they cost, especially compared with other intersections like RCIs? (3) What kind of traffic control devices (pavement markings, traffic signs, and traffic signals) are needed? (4) What movement restrictions could cause motorist confusion and violations? (5) How could we minimize those violations? (6) What are the considerations needed for pedestrian and bicyclist safety? (7) What kind of geometric and right-of-way (ROW) limitations are faced during construction? (8) What movements are less impactful for redirecting in different cases? (9) What designs would be most readily accepted by the public?
This proposed study focuses on the following three-phase designs: partial MUTs, partial CFIs, reverse RCIs, thru-cuts, offset, quadrant, CFI/MUT combo, redirect one minor leg, redirect minor lefts, seven-phase signal, and redirect two lefts and a through intersection (see Figure 1 in the body of the proposal). Also, the research team will consider other new designs, especially where another proposed design might perform better than the intersections listed above. The three-phase designs will be compared with RCI, full CFI, full MUT, and the two-phase version of the partial MUT design.