Just in time for the Thanksgiving rush home, the Texas Transportation Institute has released a national ranking of America's most-congested highway corridors. The institute, which is known for its annual mobility report of traffic in metro regions, analyzed 328 stretches of freeway at least three miles long during various periods of time. The results reach across several categories of congestion, including per-mile delay, morning and evening commute, and midday and weekend peaks.
The report's chief set of rankings is organized by what the institute calls a "buffer index." That metric is used to examine how reliable a certain corridor is during peak weekday periods. A buffer index of 50 percent, for instance, means drivers on this route should allot 50 percent more time to reach their destination without being late. (To be a bit more precise: the index asks how much time you need to make sure that in 95 percent of your trips you won't be late.) So a trip that should take 30 minutes becomes a 45-minute ride on a corridor with a 50 percent buffer index.
Here are this year's ten worst corridors by buffer index, according to the new report [PDF]:
- Atlanta — Southbound on GA Route 400, 4.1 miles from the Toll Plaza to I-85. Buffer index (BI): 256 percent.
- Atlanta — Southbound on I-75, 6.7 miles from the Mount Zion Parkway (Exit 231) to Hudson Bridge Road (Exit 224). BI: 253 percent.
- (tie) New York — Northbound on the Hutchinson River Parkway, 4.5 miles from Cross County Parkway (Exit 15) to Mamaroneck Road (Exit 22). BI: 215 percent.
- (tie). New York — Northbound on the Bronx Whitestone Expressway, 3.4 miles from Linden Place (Exit 14) to the Toll Plaza. BI: 215 percent.
- Norfolk, Virginia — Eastbound on the Hampton Roads Beltway (I-64), 3.1 miles from Rip Rap Road (Exit 265) to the Hampton Roads Bridge Tunnel. BI: 198 percent.
- New York — Northbound on the Pulaski Skyway, 3.3 miles from I-95 to Tonnele Avenue. BI: 197 percent.
- New Haven, Connecticut — Westbound on I-84, 3.4 miles from I-691 to Austin Road (Exit 25A). BI: 189 percent.
- Houston — Eastbound on I-610, 4 miles from U.S. Route 290 to Yale Street. BI: 188 percent.
- Pittsburgh — Eastbound on I-376, 3.4 miles from Lydia Street (Exit 2) to U.S. 19/PA Route 51 (Exit 5). BI: 186 percent.
- Riverside, California — Northbound on the Ontario Freeway (I-15), 6.2 miles from I-210 (Exit 115) to the Glen Helen Parkway. BI: 182 percent.
The report provides the buffer index for all 328 corridors included in the study, as well as the top 40 routes for all categories measured. In the ranking of everyday congestion, as measured by per-mile delay, highways in Los Angeles occupied 7 of the top 10 spots, with two in San Francisco (tied for 8th) and one in New York (4th) filling out the rest. The worst morning commute occurs on I-405 southbound in Los Angeles, and the worst afternoon commute is also in L.A., going northbound on CA Route 110. The Route 110 corridor also ranked worst for midday, weekend, and big truck traffic. If you're driving that road this Thanksgiving, probably not too soon to leave right ... now.