For a period of just over 20 years (1974-1995) there was a National Maximum Speed Law in place, which prohibited speed limits higher than 55 mph on interstate highways and similar access roads. The law was part of the 1974 Emergency Highway Energy Conservation Act, and was created in response to the 1973 oil crisis. Officials hoped the new speed limits would cause fuel consumption to drop. States were forced to comply if they wished to continue receiving federal funding for highway repair. However, the hoped for impact was very small as motorists largely disregarded the law and many states became lax on speed-limit enforcement. In November of 1995, congress officially repealed the NMSL, and placed authority over speed limits back in the hands of the states. Since 1995, 34 states have raised limits to 70mph or higher on some or all of their roadway systems.

Arguably, there are benefits to having one consistent speed limit in all states, but given differing geography and population density from region to region, one size does not necessarily fit all. The wide open expanses of the western states and vast distances between major population centers are seemingly better suited to higher speed limits, while roadways in congested areas in the northeast with myriad access points are believed better off at lower speed limits. Businesses that rely on interstate transportation must keep up to date on varying speed limits. Differing limits along a route may affect delivery time projections and route planning. Additionally, drivers need to pay attention as they cross over state lines, making sure not to violate speed limits, and potentially incurring fines and lost travel time.

This map shows current maximum speed limits (May 2015) across the U.S. Every state, except Texas, has a maximum speed limit for the entire state. Six states (Idaho, Montana, Wyoming, South Dakota, Nevada and Utah) have the highest overall maximum state speed limits at 80 mph, while Hawaii has the lowest at 60 mph. Only the state of Texas, has varying maximum speed limits ranging from 65-85mph. The majority of the state enjoys speed limits of 75mph, while the Dallas-Ft. Worth and Houston metro areas are limited to 65mph. The Austin area, and the western portion of the I-10 corridor, beginning west of San Antonio, and ending just east of El Paso boasts a limit of 80mph. And Texas Highway 130 has the highest speed limit in the country at 85mph. This toll road stretches 40 miles from Mustang Ridge (just south of Austin) to Seguin (just west of San Antonio).

Source: "US Speed Limits May 2015" by Andros 1337 - Own work. Licensed under CC BY-SA 4.0 via Wikimedia Commons -

Source: “US Speed Limits May 2015” by Andros 1337 – Own work. Licensed under CC BY-SA 4.0 via Wikimedia Commons –

State legislatures continue to revisit maximum speed limit laws, taking into consideration both economic and safety factors, and of course, political factors too! What will this map look like next year? As automobile technology continues to advance, will we see maximum speed limits in excess of the century mark? Stay tuned… and buckle up!!!