COLLEGE STATION (Texas Transportation Institute) – Traffic congestion is slowing millions of Texans to a halt daily, and the Texas Transportation Institute (TTI) is finding new ways to measure the effects of that gridlock.

TTI’s 2012 Urban Mobility Report includes a new measure of travel reliability called the Planning Time Index (PTI), which illustrates the extra time needed to arrive on time to priority appointments, such as airline departures and medical appointments. A PTI of 3.00 means that a traveler would need to allow 60 minutes for a trip normally requiring 20 minutes.

Nationally, PTIs range from as low as 1.31 (about 26 minutes for a 20 minute trip) in Pensacola, Fla., to 5.72 (nearly two hours for that same 20 minute trip) in Washington, D.C. In Texas, Austin faces the longest potential delays (its PTI is 4.26), followed by Dallas-Fort Worth-Arlington (4.00).

Houston ranked sixth-worst among the nation’s 498 urban areas for overall congestion.

Tune into tomorrow’s Real Estate Red Zone podcast for a discussion on how traffic congestion can impact Texas commerce and to find out what infrastructure changes are needed to accommodate the projected state population growth. This week’s guest is Tim Lomax, one of the authors of the TTI study.