Among the states with the highest speed limits, Texas leads the country by a clear margin: one toll road east of Austin is posted at 85 mph, and nine states (all in the West) allow 80 mph on at least some highway segments. Everywhere else tops out at 75 mph or lower.
Texas Holds the Single Fastest Road at 85 MPH
A 41-mile stretch of State Highway 130 between Mustang Ridge and Seguin carries an 85 mph posted limit, the highest of any public road in the United States. The toll road was built as a bypass for the congested Interstate 35 corridor between Austin and San Antonio, with wide lanes, gentle curves, and long sight distances designed around high-speed travel. No other state has matched it.
Away from that corridor, Texas posts 80 mph on other specified segments and defaults to 75 mph on most rural interstates and non-interstate highways. 1Insurance Institute for Highway Safety. Maximum Posted Speed Limits That gives Texas the widest range of posted highway speeds in the country.
Nine States Allow 80 MPH
Nine states currently allow 80 mph on at least part of their highway network: Idaho, Montana, Nevada, North Dakota, Oklahoma, South Dakota, Texas, Utah, and Wyoming. 1Insurance Institute for Highway Safety. Maximum Posted Speed Limits All sit in the West, where long stretches of flat, lightly traveled interstate make the higher limit workable.
Not every mile of interstate in these states is posted at 80. In Idaho, Oklahoma, Utah, and Wyoming, the 80 mph designation applies only to specified segments where transportation departments have completed engineering studies supporting the higher limit. Montana, Nevada, North Dakota, and South Dakota post 80 as the default on rural interstates. South Dakota goes further still, allowing 80 on urban interstates as well, which most of the other 80 mph states do not. 1Insurance Institute for Highway Safety. Maximum Posted Speed Limits
The 75 MPH Tier
A second group of states caps rural interstate speeds at 75 mph. This tier includes Arizona, Arkansas, Colorado, Idaho (as its base interstate limit), Kansas, Louisiana, Maine, Nebraska, New Mexico, Oklahoma, Texas, Utah, and Wyoming. 1Insurance Institute for Highway Safety. Maximum Posted Speed Limits Several of these states also run 80 mph segments; for them, 75 is the baseline before individual corridors get bumped up.
Maine is the geographic exception. Nearly every state east of the Mississippi tops out at 70 mph or lower, but Maine posts 75 on its rural interstates, urban interstates, and other limited-access roads alike. Kansas and New Mexico also post 75 across both rural and urban interstates, which is unusual: most states drop to 65 inside metro areas.
70 MPH and Below Covers Most of the Country
Most states east of the Great Plains max out at 70 mph on rural interstates. As of March 2026, roughly 20 states fall into this category, including Alabama, Florida, Georgia, Illinois, Indiana, Iowa, Maryland, Michigan, Minnesota, Mississippi, Missouri, North Carolina, Ohio, Pennsylvania, South Carolina, Tennessee, Virginia, Washington, West Virginia, and Wisconsin. 1Insurance Institute for Highway Safety. Maximum Posted Speed Limits
A few of these states allow slightly higher limits on select corridors. Michigan posts 75 mph on specified segments, and Washington does the same, though both default to 70 elsewhere.
At the bottom of the national range are Connecticut, Delaware, New Jersey, New York, Rhode Island, and Vermont, where rural interstates are capped at 65 mph. Hawaii has the lowest maximum in the country at 60.
Where Trucks Get a Lower Limit
Several states post different maximums for passenger vehicles and large trucks on the same road, so the highest number on the sign may not apply to you if you’re driving a heavy truck. The widest gap is in California, where cars can travel at 70 mph on rural interstates but trucks are restricted to 55. Montana allows cars at 80 but caps trucks at 70. Other split-limit states include Arkansas (75 cars, 70 trucks), Indiana (70 cars, 65 trucks), Michigan (70 or 75 for cars, 65 for trucks), and Washington (70 or 75 for cars, 60 for trucks). 1Insurance Institute for Highway Safety. Maximum Posted Speed Limits
The reasoning is that heavier vehicles take longer to stop and cause more damage in a crash. Whether split limits are actually safer is contested. A federal study found no statistically significant difference in accident rates or severity between states using split limits and those with uniform limits for all vehicles, but it did find that split limits increased speed variance in the traffic stream. States with differential limits saw more rear-end collisions involving cars striking trucks; states with uniform limits saw more trucks striking cars. 2Federal Highway Administration. The Safety Impacts of Differential Speed Limits on Rural Interstate Highways
Why the Numbers Vary So Much
The main tool behind these decisions is the 85th-percentile speed study. Engineers measure how fast drivers actually travel on a road under free-flowing conditions, then identify the speed at or below which 85 percent of vehicles operate. The Federal Highway Administration recommends that posted limits on freeways and rural highways fall within 5 mph of that figure, unless other safety factors warrant a reduction. On urban and suburban arterials, the FHWA advises against relying on the 85th percentile alone and calls for weighing crash history, pedestrian activity, and roadside development. 3Federal Highway Administration. Speed Limit Setting Handbook
That is why the fastest limits cluster in the West. When Idaho or Utah raises a segment from 75 to 80, it reflects a study finding that drivers were already traveling near that speed on a road built to handle it. The same logic explains why congested metro corridors rarely see increases: if traffic regularly moves well below the posted limit during peak hours, no study will support raising it.
Posted limits can change, and the exact mile markers where a limit shifts from 75 to 80, or 70 to 75, are decided segment by segment. If you’re planning a trip and want certainty about a specific stretch, check with the state department of transportation for the route you’ll drive.