Mauka to Makai

Mauka to Makai

Is Honolulu really No. 1 in traffic jams?

Mauka to Makai / A recent finding that Honolulu is No. 1 in traffic congestion in the US is being touted by some as proof that the city needs heavy rail. But wait. Is the data reliable? The source, INRIX, is a spinoff of Microsoft Corp., based in Kirkland, Wash., which has developed into a major player in the analysis of massive traffic information datasets. Their data come from tracking cell phones of motorists in traffic. On the mainland, they also collect information from AVL (Automated Vehicle Location systems, installed on several hundred thousand commercial vehicles in the trucking, delivery and logistic supply chain operations). Their GPS-based tracking is substantially more accurate than cell-phone tracking.

But in Honolulu, INRIX data is limited to cell-phones and can be erroneous due to the density of the road network. For example, the INRIX database cannot distinguish between a vehicle on the H-1 Freeway near Piikoi Street and a vehicle crawling next to the viaduct on Lunalilo Street.

Moreover, INRIX reported conditions for more than 40 corridors in LA with a length of more than 300 miles. INRIX reported conditions for only two corridors on Oahu–a total length of 11 miles, both including the Middle Street and Kalihi Street freeway bottlenecks. So the data from Oahu represents the most severe conditions and is not representative of island commutes.

INRIX’s finding of Honolulu as the No.1 congested city in the nation is in clear disagreement with the TTI congestion index, which ranks Honolulu No. 50. In the table above, if Honolulu is excluded for a moment, both INRIX and TTI (Column 7, “Congestion Rank”) rank LA as No. 1. INRIX and TTI results are very similar for New York City. Then INRIX reports higher congestion for San Francisco (No. 3) than TTI (No. 11). Again, in San Francisco INRIX focuses on congested corridors and overestimates congestion. The lesson here is that the scientific TTI index of the University of Texas is more reliable and representative of traffic congestion in US metropolitan areas.

This fact did not stop Move Oahu Forward and Honolulu Authority for Rapid Transit (HART)’s Grabauskas from using Honolulu’s INRIX No. 1 ranking in traffic congestion as a reason that Honolulu needs rail to solve its traffic problem.

However, as the table shows, except Honolulu, all the top 15 worst cities for traffic congestion have rail! Rail systems have clearly failed to relieve congestion from our most congested cities.

What did rail really do for the congestion of these top 14 cities on the INRIX list? It squandered billions of dollars which could have been used for real traffic relief. This is now the plan for Oahu. Roughly half of all transportation monies will go to rail. Congestion will get worse.

Honolulu’s traffic congestion problem is simple: We have too many localized bottlenecks, underfunded city traffic operations, a rather lethargic state DOT and too few lanes, as the graph shows. Adding a few lanes will go a long way toward relieving congestion in Honolulu.

The final lesson here is that Honolulu’s congestion ranking is No. 50. But with rail, it stands a good chance to climb to the top 10 congested cities in the US.

The writer is Professor of Civil and Environmental Engineering at UH Manoa.