07/01/2026
Great explanation of our changing roadway speeds.
This new law does NOT affect all two lane roadways. Additionally, it will take some time to update speed signage.
1. What is the legislation that caused the Speed Limit change?
Senate File 378 was passed by the 2026 Iowa Legislature and signed by Governor Reynolds. The legislation changed Iowa Code 321.285(3) to establish the default speed limit of 60 mph for any roadway where state law does not otherwise designate a limit. The prior speed limit was 55 mph.
2. What else did the legislation change?
Senate File 378 made other changes in different sections of Iowa Code 321 to adjust provisions relating to speeding violations that reflect the adjustment from 55 mph to 60 mph. Iowa DOT’s Motor Vehicle Division is aware of those impacts and is adjusting its processes as needed.
3. What are the laws that set speed limits?
Iowa Code 321.285 establishes most speed limits. Iowa Code 321.290 authorizes Iowa DOT and cities to establish other speed limits on their respective roadways based on engineering and traffic studies. Iowa Code 321.285(4) likewise authorizes counties to establish other speed limits on county roads based on engineering and traffic studies.
4. Where is the default speed limit typically used?
The default speed limit in Iowa Code 321.285(3) is used on any roadways where a speed limit is not otherwise established under any other provision of 321.285, or where a speed limit is not based on an analysis by Iowa DOT or cities under 321.290 or by counties under 321.285.
The most common use of the default speed limit is on two-lane paved rural roadways, including on the state primary roadway system and the county roadway system. While there are some multi-lane roadways with a 55-mph speed limit, those limits have mostly been established through specific engineering and traffic analyses and generally will not be increased to 60 mph.
5. When will updated speed limit signs be installed on the Iowa DOT’s Primary Highway System?
Iowa DOT is working to update most signs on the primary roadway system starting on July 1, 2026, with priority given to the most heavily traveled roads. County governments are responsible to update signs on county roads. Iowa DOT has worked with the Iowa County Engineers Association to publicize the change and the July 1 effective date. City governments are also responsible to update limits on city road, if applicable.
6. Will Iowa DOT install all new signs or modify existing signs?
Iowa DOT plans to use aluminum overlays to immediately change most existing signs from 55 mph to 60 mph. If any existing signs were already slated for replacement, then the Iowa DOT may choose to install a new sign if that can be done around July 1. Future sign replacements will proceed as scheduled. Counties and cities may use either overlays or sign replacements on roads in their jurisdictions.
7. Will other signs or markings need to be changed?
Iowa DOT is reviewing impacted locations to determine the need for other signs and markings to be added or changed. These could include any of the following (along with other geometric features) and the analyses may extend into 2027:
· “Reduced Speed Limit Ahead” signs, typically used for changes of more than 10 mph
· Curve Warning and chevron signs
· Signs and pavement markings at no-passing zones
· Guardrail lengths protecting fixed objects, and other features
8. How many signs are impacted? What is Iowa DOT’s cost for the change?
Iowa DOT will need to change approximately 1,800 existing 55 mph signs on the state primary roadway system to 60 mph. The initial process for the immediate change will cost about $270,000. Iowa DOT may incur other signing and marking costs based on the supplemental analyses of corridor needs.
9. Will every roadway that is currently at 55 mph be changed immediately?
The majority of the approximately 1,800 55 mph signs will be changed to 60 mph beginning on July 1. Iowa DOT anticipates about a week to change out most of the signs.
For certain locations currently signed at 55 mph, Iowa DOT may need to investigate the engineering and traffic details at that location to ensure the proper speed limit. For example, there are curves on primary highways that may not be suitable for higher speed limits. Factors include the context of the location (urban/rural), the road environment, the roadway characteristics, the crash history, current traffic speeds and development in the area. These engineering and traffic analyses are performed under the authority of Iowa Code 321.290 to ensure safety. Any existing speed limit signs remain legally binding until or unless the Iowa DOT posts a new sign.
County governments also have authority 321.285(4) to establish speed limits other than the default based on engineering and traffic studies. Cities have authority under 321.290.
10. If a road qualifies for the new default speed limit, but the sign hasn’t changed, what speed should motorists drive?
Since Iowa Code allows Iowa DOT and counties to establish other speed limits based on engineering and traffic studies, it is safest for motorists to obey the posted speed limit even if they believe it may change from 55 mph to 60 mph. Existing posted speed limits established through engineering studies remain valid and enforceable. As noted, it may take a short time for Iowa DOT and counties to change all signs. It is also safer if all motorists obey the posted speed limit to minimize speed differential or confusion.
Iowa DOT is working with Iowa Department of Public Safety to inform them of the timing and highway locations of the changes. DPS will also coordinate as needed with County Sheriffs to inform them of the change.
11. Has the Iowa DOT consulted with their legal counsel?
Yes. The Attorney General team assigned to Iowa DOT has indicated that the posted speed limit is the legal limit, even if a roadway is defined as “default” by law. AG’s assertion is that DOT (or county or city) is responsible to determine if a road should still be at the default so no one should assume that a roadway that previously had a default speed limit (55 mph) will still be at the higher default speed limit (60 mph). It is also safest for motorists to obey the posted speed because an individual motorist will not know if a 55 MPH limit is (a) on a default road where the limit is yet to change; or (b) specifically designated to be 55 by the state/county/city based on an engineering analysis.
