TTI Traffic Rankings Challenged

"TTI doesn't base its conclusions on what's really happening on freeways at rush hour. Lomax and his colleagues don't consider how fast traffic is actually moving on the Evergreen Point Floating Bridge or the San Diego Freeway at 5 p.m. Instead, they use a database from the Federal Highway Administration that contains relatively limited information: miles and lanes of freeway and arterial in each city, and the average daily traffic volumes on each road segment. They produce their measures and rankings by applying assumptions and estimates to that data. That's where the problem lies, critics say." [Editor's note: Although this story is from early June, several readers have written to let us know we haven't covered the dispute over the TTI ranking carefully enough, and reader Christopher Zegras from MIT specifically recommended this story. Thanks to all who wrote in.]

Thanks to Chris Steins