If you had to guess which Census tract in the Dallas area had the worst commute, which would you choose? McKinney, maybe? One of the far-flung Fort Worth exurbs popping up in Denton and Tarrant County?
If so, you'd be way off. The lone spot of dark brown on the Census Bureau's newish commuting map, the melanoma representing nightmare commutes averaging 45 minutes or more, is in Lake Highlands. The typical commute there is 49 minutes.
What gives? Mostly this seems to be the product of small sample size. The Census tract in question -- 78.26 -- is a tiny sliver dominated by the leg of White Rock Creek, DART's Blue Line, and the considerable footprint of the as-yet uninhabited Lake Highlands Town Center.
As of the 2012 American Community Survey, the area contained all of 161 working adults, 15 percent of whom (about 25 total) had commutes of an hour or more. And unlike the Census that takes place every 10 years, the isn't an exhaustive enumeration but a random sample which is why the margin of error on the 49-minute figure is 38. The average commute could be 11 minutes or it could be 87. In other words, basically meaningless.
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Expect the commute time to drop dramatically once the population in that area more than quintuples in the coming years.
Compare the Lake Highlands tract with a random Census tract in McKinney. That contains a much larger sample size -- about 3,000 workers -- meaning the average commute time of 24 minutes is far more accurate.
Statistical quirks aside, the most striking thing about the map is probably the north-south (and rich-poor) divide. The Uptown-Park Cities-Preston Hollow corridor has some of the shortest commute times in Dallas County. The South Dallas-Pleasant Grove corridor, by contrast, has some of the longest.
Send your story tips to the author, Eric Nicholson.