Comparison of the New W-lnterchange with Conventional Interchanges

Congestion is a problem at many urban interchanges, particularly at diamond interchanges. A new interchange design, called the W-interchange, seeks to reduce congestion at a reasonable cost. Similar to the Michigan urban diamond interchange (MUDI), which uses U-turn structures, the W-interchange attempts to reduce delay by eliminating the left-turn movements onto and off of the cross street. The new W-interchange was compared with other, more commonly used designs for freeway-to-arterial interchanges, specifically the diamond interchange, the single point urban interchange (SPUI), and the MUDI. A major portion of the effort was a comparison of the travel times and stops across a range of traffic demands using a microscopic traffic simulation package. The results from the simulations indicated that the W-interchange minimized the number of stops and produced an overall travel time that was lower than the diamond interchange and comparable with the MUDI. The W-interchange had lower travel times than the SPUI for a few of the cases simulated, but generally the SPUI had lower travel times. A design of the W-interchange was created to estimate its construction and right-of-way cost. At about $14 million, the W-interchange costs about $4 million more than the SPUI and about $6 million more than the diamond interchange. Overall, the W-interchange performed well enough in the simulations and has enough other advantages to justify further research in the areas of cost, signing and marking, continuous frontage road operation, and a possible freeway-to-freeway design.