Miles of Texas highway will soon see speed limit increases after the Texas Transportation Commission action approved 75 mph designations for almost 1,500 miles of interstate.

The speed limit changes span 60 Texas counties, making it the largest conversion since a new law was passed that allows the Texas Department of Transportation to establish 75 mph speed limits on Texas highways providing speed studies show it can be done safely.

Since September, the agency has been reviewing existing 70-mph speed limits across the state to determine where a 75-mph limit may be safely posted. The most recent Commission action brings the number of miles now zoned at 75 mph to 1,618.

New 75-mph speed limits approved Thursday are located on:

* I-10, 289 miles across El Paso, Gillespie, Kerr, Kendall, Bexar, Guadalupe, Caldwell, Gonzales, Fayette, Colorado, Austin, Jefferson and Orange counties

* I-20, 423 miles across Crane, Ector, Midland, Martin, Howard, Mitchell, Nolan, Taylor, Callahan, Eastland, Erath, Palo Pinto, Van Zandt, Smith, Gregg and Harrison counties

* I-27, 109 miles across Lubbock, Hale, Swisher and Randall counties

* I-30, 139 miles across Hunt, Hopkins, Franklin, Titus, Morris and Bowie counties

* I-35, 106 miles across Webb, Medina, Atascosa, Bexar, Hill and Cooke counties

* I-37, 130 miles across Nueces, San Patricio, Live Oak, Atascosa and Bexar counties

* I-40, 166 miles across Deaf Smith, Oldham, Potter, Carson, Gray, Donley and Wheeler counties

* I-44, 11 miles across Wichita County

* I-45, 143 miles across Walker, Madison, Leon, Freestone and Navarro counties

"Texas' economic strength depends on the efficient and safe movement of people and goods," says Carol Rawson, TxDOT traffic operations division director. "These new speed limits increase highway efficiency while maintaining the safety of the transportation system."

Motorists must continue to travel at the posted speed until new signs are installed, said Rawson.

Go here for more information on the locations of the new speed limits.