FHWA Overstates Houston Driving by 50 Percent --- Again

New (2006) Federal Highway Administration data for urban area highway use has just been released. As usual, the Houston area is wrongly shown as having the highest daily vehicle miles traveled per person among the nation’s urbanized areas of more than 1,000,000.

The erroneous 36.0 miles per capita is the result of a reported urbanized area (urban footprint) population of 2.8 million and a daily travel figure of 101 million miles. This 2.8 million population is reported to live in 1,476 square miles.

In 2000, FHWA reported Houston’s urbanized area population to be 2.5 million in an area of 1,537 square miles. The same year, the US Bureau of the Census found the Houston urbanized area to cover 1,295 square miles and to have a population of 3.8 million --- a full 1.3 million above the FHWA number. It is, of course, impossible for the FHWA’s larger urbanized area to have 1.3 million fewer people than that of the census. The result was then, and is today, a huge over-estimation of the daily vehicle miles traveled per capita.

Some years ago I brought this issue to the attention of the United States Department of Transportation. A bureaucrat condescendingly wrote me that Census urbanized areas and FHWA urbanized areas were different things, not comprehending the irreconcilable and irrational differences I had pointed out. There used to be similar problems with the Atlanta data, but it has since been fixed. In 2003, FHWA reported Atlanta at 34 miles per capita daily and, now, having adjusted its population estimate to a more rational figure. Daily travel is now reported at 29 miles per capita.

While the Bureau of the Census does not update urbanized area populations and land areas between decennial censuses, Houston’s metropolitan population growth would indicate an increase to in the neighborhood of 4.4 million in 2006. On that assumption, Houston’s daily vehicle miles traveled per capita would be 22.7, 20 percent below San Antonio, 10 percent below Dallas-Fort Worth, lower than Los Angeles and only 10 percent higher than Portland.

Note: The American Community Survey of the United States Census Bureau publishes yearly estimates of the population within urbanized areas as delineated in the 2000 census, but does not update the land area or include population that is added to the urbanized area in land area not included in the 2000 land area definition.