Iowa raised its rural statutory default speed limit from 55 to 60 mph, taking effect on 1 July 2026 (Code 321.285(3)). Only paved roads move to 60. And 60 is a default; posted-lower limits still apply and signs are going up gradually.
I’ll update the Default speed limits wiki page after July 1. But there are also a few thousand rural Iowa segments tagged maxspeed=55 that look like the old default rather than surveyed postings. I’d like input on whether it’s worth updating the clearly-paved ones (n = 1,696) to 60 mph, scoped tightly:
currently maxspeed=55 mph
highway unclassified through trunk (no motorway; residential included since rurally it’s a de-facto minor road, not a 25 mph residence district)
surface = asphalt/concrete/paved. Excludes unpaved and unknown
US Census rural areas only (imperfect, I know)
source:maxspeed is not “sign” and maxspeed_type is not “sign”
Rather than just flipping numbers, I’d dual-tag: maxspeed=60 mph + maxspeed:type=US-IA:rural, so it’s clearly default-derived and self-documents for the next change. (Iowa has no implicit tagging yet; US-IA:rural follows the legal-default-speeds library)
The risk: we can’t tell from the data which 55s are genuine postings that will remain effective, versus old defaults. Speed limit data sources for Iowa are almost never explicitly tagged; I only found 14 instances of otherwise-eligible ways, compared to the remaining 1,696 I mentioned)
Would it make sense to go forward with this 60 mph change for the overall benefit, or leave as-is and wait for local knowledge to hopefully trickle in?
Edit - forgot to add this initially: Disclosure: I currently work at Geotab and handle the backend speed limit data behind fleet speeding alerts, so I have a professional interest - but we can handle this internally and I don’t need the OSM change. My motivation is that if these edits are valuable, I’d like to contribute them back. If it goes ahead I’ll put up an Organised Editing Activity page.)
This sounds like a valuable project. I think you’ve recognized the key difficulty of this. One way to identify previous statutory speed limits would be to identify if many ways were changed in one changset. You may want to get on the OSMUS slack channel to get a little more lively discussion of the issues or some more ideas.
FYI, maxspeed:type=US-IA:rural might have a second meaning that the neighborhood feels “not built up” to the mapper. There’s some discussion about curbing that interpretation before it dilutes the meaning of this useful tag:
KCRG TV news just ran a story today saying that Dubuque County is planning to pass an ordinance reverting these speed limits back to 55 mph. The landscape within the county is hilly, so there are serious concerns about the safety of raising the speed limit. They said that they may conduct studies and raise individual roads up to 60 mph, but not the entire county.
Unfortunately I’m only local enough to see this on the news, but too far away to go out and survey the area. But caution should be taken before a bulk edit on the roads in Dubuque County, or if already done, a local could help by surveying actual signage).
EDIT: They have an article on their website as well now.
I have too much experience with speed limits and getting them organised properly - 22 years, 31 cities and counties and on average a review every 5 years.
Might the state and/or counties share their data? Important: their data might not be correct, legally or otherwise.
It might make sense for someone locally to put together the hierarchy of how, legally, speed limits are implemented in Iowa (what are the defaults, who can change them, what subsidiary laws and ordinances have been passed, etc.) and then work out how that affects each category of road. For this purpose, you can somewhat ignore the engineering, psychological and social concepts related to speed limits and concentrate of the legal situation.
It is just possible that there is state-issued guidance / leaflets / engineering manuals already in existence. Attorneys might also have created their own documents.
Having a look at some specific roads, might many of them be badly classified? There are many highway=residential with less than 1 house per mile.
Iowa, highway=* from: https://dashboard.ohsome.org/
Motorway 4,100 km
Trunk 3,506 km
Primary 10,642 km
Secondary 23,318 km
Tertiary 25,915 km
Unclassified 13,078 km
Residential 112,603 km
Service 44,774 km
Track 4,808 km
The only thing that we’d be really confident in is what the sign says. When there isn’t a sign, it gets weird, as that other thread demonstrates. Prima facie speed limits are often based on factors that we as mappers can only guess about. In Iowa, the increase from 55 to 60 miles per hour applies outside business, residence, school, and suburban districts, defined as follows:
“Business district” means the territory contiguous to and including a highway when
fifty percent or more of the frontage thereon for a distance of three hundred feet or more is
occupied by buildings in use for business.
“Residence district” means the territory within a city contiguous to and including a
highway, not comprising a business, suburban, or school district, where forty percent or more of the frontage on such highway for a distance of three hundred feet or more is occupied by dwellings or by dwellings and buildings in use for business.
“School district” means the territory contiguous to and including a highway for a
distance of two hundred feet in either direction from a schoolhouse in a city.
“Suburban district” means all other parts of a city not included in the business, school,
or residence districts.
At a glance, what counts as a business or dwelling for this purpose probably isn’t very clear. One hopes that there are speed limit signs anywhere it’s really ambiguous, but you never know.
That said, I do think we can feasibly carry out a mechanical edit like the one @emilyeros proposes. The state code only allows localities to lower the statutory speed limits, not raise them. So the 55 mph value could’ve only gotten there in two scenarios:
Via section 321.285, subsection 3, which is what changed. If the speed limit was incorrect before, it’ll continue to be incorrect after the proposed edit. An additional 5-mph error would not be quite as dramatic as the potential 30- or 40-mph errors coming from the design flaw in StreetComplete.[1]
Via section 321.285, subsection 5, which sets fully controlled-access highways and some divided highways at 65 mph, followed by local action to lower the speed limit to 55 mph. This isn’t affected by the recent legislative change. I think excluding highway=motorway and expressway=yes should be enough to avoid this case.
So far, only five ways have been tagged maxspeed:type=US-IA:*, all by StreetComplete. Indeed, the streets have no speed limit signs, but legal-osm-default-speeds luckily will match the Ankeny Municipal Code. ↩︎