Reuters/Lucy Nicholson

More than 40 percent of congestion delays occur during off-peak hours

The 2011 Urban Mobility Report [PDF] came out yesterday, and one of its clearest conclusions is that "rush hour" is a terrible misnomer. The hour of congestion at the start and close of the average workday can expand to about six hours in some large metro areas. The worst time to be on the road is in the evening — 14 percent of daily delays occur from 5 to 6 p.m., with about 12 percent taking place from 4 to 5 p.m. — but traditional off-peak hours aren't much better. About 30 percent of a day's delays occurs during the midday hours, roughly 10 a.m. to 3 p.m., and two-fifths of all daily delays occur outside traditional rush-hour periods.

These findings are particularly interesting when compared to another commuting chart released last week by the U.S. Census [PDF]. This data, which shows commute time based on hour of departure, was collected as part of the 2009 American Community Survey of U.S. metropolitan areas. Take a look first at the orange and light blue bars in the "drove alone" group. This shows that for the average car commuter in the average metro area, it took as long to get to work during rush hour (8 to 9 a.m.) as it did during midday (noon to 4 p.m.):
Now that finding doesn't mean roads are congested during the middle of the day, per se. It could mean that people who leave for work in the middle of the day drive farther to their workplace. Still, the end result is a similar quality of life. Either you spend a good deal of time in the car getting to work in the morning while sharing the roads with everyone else, or you spend the same time on the road but have a little more space to move. If anything, this dilemma is the best-case scenario. The alternative is that off-peak congestion is getting worse and commuting midday doesn't benefit people like it used to.
Another interesting point from the ACS figure is the length of commutes that begin in the wee hours. That finding may suggest that people with very long commutes leave very early in the morning. But it may also mean, as transit blogger Alon Levy points out, that late-night commuters "live on the wrong side of their metro area or in low-income exurbs, and need to drive considerable distances to the favored quarter." In other words, workplaces aren't located near residences for part of the population — most likely low-wage workers who can only afford to live across town.
The 2011 Urban Mobility Report contained a few other notable conclusions. Commuters in Washington, D.C., spent the most time in congestion in 2010, at 74 hours; rounding out the top five "very large" cities were Chicago (71 hours), Los Angeles (64), Houston (57), and New York (54). The report also included a list of 42 metro areas where road demand was outpacing road supply by more than 30 percent [PDF]. 
Perhaps its most useful chart examined the efficiency of H.O.V. lanes [PDF]. These lanes are designed to maintain traffic flows at around 60 mph., yet a few don't come anywhere close. A 4.5-mile H.O.V. lane on SR-57 in Los Angeles, for instance, averaged 27 mph during rush hour. Another poor stretch, along 6.7 miles of interstate in Portland, cruised at 34 mph.
In past years the Urban Mobility Report, which evaluates traffic in 439 metro areas and is released annually by the Texas Transportation Institute, has been criticized for faulty data analysis methods. This year's report seems set up for some fire as well. While Baltimore commuters suffered the worst "large" city annual delay, at 52 total hours, for instance, the city finished 67th in total peak-period travel time, at 83 minutes a week. Jackson, Mississippi, meanwhile, finished second on that metric, at 126 minutes of peak travel a week.
The Jackson figures are pretty hard to fathom, in part because of common sense, and in part because other data show that only about 4 percent of workers there commute more than an hour. At least the current report recognizes the problem: "Any measure that appears to suggest that Jackson, Mississippi, has the second worst traffic conditions and Baltimore is 67th requires some clarification."

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