Panos Prevedouros, PHD

BY PANOS PREVEDOUROS PHD – Urban underpasses are the key to central city congestion reduction given that there is no room to widen streets and there is no desire to build intrusive flyovers. Here is a short video that explains them.

Honolulu would greatly benefit from at least three express underpasses. One from Nimitz to Alakea and Halekawila, another on Kapiolani Boulevard at the Kapiolani/Date/Kamoku intersection by Iolani School, and a third by having a lane of Kalakaua Avenue go under Kapiolani Boulevard.Here is a video of our traffic simulation that explains the one lane express underpass from Nimitz to Alakea and Halekauwila. Observe that the left turns that take a long time to receive green and spill over and block lanes on Nimitz Highway flow non-stop to both Alakea St. and Halekauwila St. Also the westbound (Ewa) flow has green light all the time except when there are pedestrian crossing requests.

The simulation screen-shots below show the before/after situation on Kapiolani Boulevard at its intersection with Date and Kamoku streets. The one lane per direction underpass visibly reduces congestion on Kapiolani Boulevard and allows for more green time to be allocated to the other sides of this complex intersection. This reduces their congestion and shortens the waiting time for the pedestrian crossings.