Jefferson County supervisors discussed the financial and logistical implications of Iowa’s new statewide speed limit law during Monday’s meeting on June 29th, while also formally approving an extension of the 45 mph speed zone on Libertyville Road that had been discussed at the June 22nd meeting.
New State Law Raises Default Speed Limit to 60 MPH
Beginning Wednesday, July 1st, the default speed limit on most rural, two-lane state highways and paved county roads across Iowa will rise from 55 mph to 60 mph under Senate File 378, which amended state code to establish the higher limit unless a county has taken formal action to maintain a lower speed limit through a resolution, ordinance, or documented engineering study.
The Henry County Sheriff’s Office has reminded drivers that they must still obey whatever speed limit is currently posted — the higher limit only applies once signage has actually been updated to reflect it, and some roads may retain a lower posted limit due to road design and safety concerns.
The Jasper County Sheriff’s Office offered similar guidance, noting that the Iowa Department of Transportation has confirmed through its legal counsel that the posted speed limit remains the legal limit regardless of whether a road is technically classified as a “default” roadway under the new law. According to the Attorney General’s office, no motorist should assume that a road previously posted at 55 mph has automatically become 60 mph — that determination is up to the DOT, county, or city responsible for the road, and it may take time before new signage reflects the change. Officials say it is safest for drivers to obey whatever is currently posted to avoid confusion or unsafe speed differentials between vehicles.
Keokuk County is facing a similar transition, as is the rest of the state. Keokuk County Emergency Management has urged drivers to pay attention to posted signs as the update process takes place there as well. According to the Iowa Department of Transportation, approximately 1,800 existing 55 mph signs on the state primary roadway system statewide will need to be changed to 60 mph, with an initial estimated cost of approximately $270,000.
The DOT plans to use aluminum overlays to immediately convert most existing signs rather than replacing them outright, a method similar to the reflective stickers Jefferson County is considering for its own signage. The DOT anticipates the bulk of the roughly 1,800 signs on the primary system will be updated within about a week of the July 1st effective date, though additional reviews of curve warning signs, reduced speed limit ahead signs, and no-passing zone markings may continue into 2027. The DOT noted it may incur additional signing and marking costs depending on those supplemental corridor analyses — a cost structure that mirrors the concerns Jefferson County officials raised about their own secondary road system.
County Engineer DeWayne Heintz presented supervisors with guidance materials outlining how counties should respond to the change, including FAQs distributed by state engineering associations. Heintz explained that without a resolution or documented engineering study justifying a lower speed limit, the county’s existing 55 mph signage will not be legally enforceable after July 1st.
Supervisor Lee Dimmitt asked directly whether the county would be in violation of the law if signage was not updated. “So I do have a question — the way I read the law, we have, as do cities, the posted speed limit, but then they said we had to do a traffic count. Is that correct?” Dimmitt asked. After Heintz clarified the requirement was an engineering study rather than a traffic count, Dimmitt pressed further, asking whether the county would be out of compliance if signage was left unchanged. Heintz confirmed that it would be. Dimmitt also asked who would be responsible for monitoring compliance, while Supervisor Susie Drish raised concerns about potential penalties. “I was kind of wondering what the penalty would be,” Drish said.
Heintz explained that the practical consequence would fall on local law enforcement. “Nothing other than it would be a pain in the butt for the Sheriff’s Department, because they’ll be writing speed tickets that people can then turn around and take to court and say, well, the speed limit’s supposed to be 60,” he said. He added that the 55 mph speed limit would not be enforceable unless the Board of Supervisors passes a resolution addressing the affected roads. “Technically the 55 mile an hour speed limit is not enforceable unless the Board of Supervisors passes a resolution,” he said, noting it could be done as a blanket resolution, “but we would need to basically list all of the roads that were affected.”
What Qualifies as an Engineering Study
Dimmitt asked about the process required to justify keeping a lower speed limit on a given stretch of road. Heintz explained that the guidance on what constitutes a sufficient engineering study is vague. “The guidance is very vague on what constitutes an engineering study,” he said. “If I drive a road in the county at 60 miles an hour and feel that it’s unsafe, that could qualify as an engineering study. So it can be based on judgment alone.” He described using a wheel, cone, and reading rod on Libertyville Road to measure sight distances at specific points, as well as a device called a ball bank indicator that measures whether a vehicle has exceeded safe limits while navigating curves.
Supervisor Joe Ledger asked whether counties had the option to simply maintain the existing 55 mph limit countywide rather than going through a road-by-road review. “Is there anything in here that says each county can make the determination as to whether to raise it to 60 or keep it at 55?” Ledger asked. “Because I had a conversation over the weekend with somebody, and that’s what they indicated it was supposed to have been in there.” Heintz confirmed that the law does not allow for that approach. “No, it’s statutory,” he said. “So it is state law that, unless posted otherwise, it is 60 miles an hour, unless an engineering study has been done to justify a lesser speed limit.” Ledger replied, “So I was kind of… didn’t understand it right, or misled, or whatever.”
Heintz acknowledged the confusion is understandable. “Well, they have very poor guidance in the legislation,” he said. “So this is what the lawyers at the DOT and the Service Bureau kind of came up with as the most defensible actions you can take.” Ledger noted he had argued with someone over the weekend about how impractical a county-by-county approach would be. “There’s 99 counties,” Ledger said. “It’s going to be hard to do that.” Heintz agreed that was likely the legislature’s intent. “And I’m guessing that’s why they worded it the way they did,” he said. “Isolated sections that we know don’t justify or aren’t safe with a higher speed limit, we can do by ordinance or resolution. But I don’t think we can do the whole county, which would make my life a lot easier.”
Cost Concerns
Dimmitt raised concerns about the financial burden the change will place on the county, and said he wants a cost estimate before any further action is taken. “Before we change anything, I’d like to know what it’s going to cost,” he said. Drish agreed.
Dimmitt was critical of the state for shifting the financial burden of the change onto counties. “I’m going to have a conversation with our state legislators, because I think the state should be paying for it,” he said. “They’re making the change. The county shouldn’t be paying for it.” He continued, expressing frustration with how counties are perceived. “They’re talking about what kind of ***holes we are because we’re charging the hell out of everybody on the property tax, and then they come along and do something like this,” Dimmitt said. Heintz responded in agreement. “Preaching to the choir, my friend,” he said.
Heintz explained that some costs will be minimal — reflective stickers to update existing 55 mph signs across the entire county were estimated at roughly $600 total. However, more significant costs will come from relocating speed zone ahead signs, extending no-passing zones, and adjusting rumble strip placement to reflect the new speed thresholds. He noted that no-passing zones will generally need to be extended by approximately 150 feet to account for the difference in sight distance required between 55 mph and 60 mph speed limits. Heintz said he had not yet tallied how many no-passing zones or speed-zone-ahead signs across the county would ultimately need to be addressed.
Heintz estimated signage material costs at roughly $60 per sign, with labor potentially tripling that cost when accounting for staff time to drive the county and complete the work. “I figure it’s $60 per sign, and you’re going to have to pay somebody to drive around the county in their truck and do that, so you might as well triple the material cost,” he said. He cited a prior bid of $650 per sign for remove-and-replace work completed on Libertyville Road, where signs were concentrated in one location, as a point of comparison for more spread-out work across the broader county road system. “That’s what we paid, I believe, for remove-and-replace signs on Libertyville Road, where they’re all in one spot,” Heintz said.
Dimmitt said the cost would vary significantly depending on the number of roads affected, but estimated it could be substantial. “Statewide, I’m sure it’s well over a million dollars,” he said. Ledger reacted to the scope of the undertaking. “No kidding. No kidding,” he said.
Libertyville Road Resolution Formally Approved
Supervisors also formally passed the resolution to extend the 45 mph speed zone on Libertyville Road from its current location southwest of the Highway 34 overpass to house number 1871, an action discussed in detail at the June 22nd meeting but not finalized at that time due to the resolution not being prepared in advance. The motion passed unanimously.
