Open Access Dissertation
Date of Award
Civil and Environmental Engineering
JOSEPH E. HUMMER
These days, alternative interchanges are attracting the attention of transportation
agencies and designers more than ever. Most of the existing interchanges in the U.S
were built in the 1950s and 1960s when traffic volume was much lower, and the type of
vehicles and driving habits were completely different. Moreover, the knowledge of
highway design and safety is more developed now, and this provides an appropriate
situation to increase the efficiency of interchanges regarding traffic operation and safety
using alternative interchanges.
This research evaluated the performance of two proposed service interchange
designs—the synchronized design which is related to a superstreet intersection and the
Milwaukee B design that is related to a parclo B design--as possible substitutes where
existing interchanges are failing. Over 1700 simulation tests modeled the traffic
operation, pedestrian performance, and safety of six different interchanges (two new
and four existing interchanges) in different conditions of traffic volume, traffic
distribution, left/right turning volume ratios, and heavy vehicle percentage. Then, a cost
estimation and validation procedure were also conducted to complete the analysis.
Overall, the Milwaukee B showed the best traffic operation among all the
interchanges. The synchronized interchange looks promising as a substitute for a
diamond interchange with dominant through traffic. The synchronized and diverging
diamond interchanges (DDI) showed almost the same results while handling moderate
levels of turning volume; however, the synchronized performed better than the DDI in
low turning volumes while the DDI can be a better choice in high turning ratios.
Regarding the safety, the DDI and Milwaukee B were the safest designs based on
observed conflicting interactions in the simulation models; however, the DDI did not
seem as reliable from the viewpoint of unusual maneuvers and wrong way movements.
The new synchronized interchange, the parclo B, and the Milwaukee A (an existing
interchange in Milwaukee, WI) showed the same rate of conflicts. The synchronized
interchange may be advantageous because it was estimated to reduce the severity of
crashes due to fewer crossing conflicts, a lower speed of conflicts, and a higher time to
collision. The results of the pedestrian analysis indicated that a relatively safe condition
is expected for pedestrians in the proposed new designs in comparison to the existing
interchanges. The DDI, one of the most popular alternative interchanges, showed the
worst performance in all the aspects of the pedestrian analysis.
Mehrara Molan, Amirarsalan, "Evaluation Of Milwaukee B And Synchronized As New Service Interchange Designs" (2017). Wayne State University Dissertations. 1845.