Ioawa: Headache with default speed limits

Hey there, again. As you see, I am going on about this alphabetically :slight_smile:

I added the speed limits I read in the law text for Iowa in the table under (US-IA) here now, but there are some unclarities for me. Perhaps (someone from Iowa) can help me there?

1. Unclear rule
So, there is this:

I am having difficulties to understand (4). So, the default, if nothing else applies, is 55 mph, but during night, it is 50 mph on secondary roads that are not paved with with asphalt or concrete?
(And then, what are secondary roads? It is not defined in § 321.1 Definitions of words and phrases)

2. Are “school districts” always just signed as such, or is the speed limit that applies for these school districts also signed?
If the speed limit that goes with school districts is always signed, this rule doesn’t need to be in the OSM default speed limits table.

3. How would a driver know that he is in a “suburban district” (and not in a residence or other district)? (45 mph)
“Suburban district” is also not defined in § 321.1 Definitions of words and phrases. Or, again, will there always be speed limit signs at the borders of these districts?

4. How would a driver know that he is on a “state park or preserve drive”? (35 mph)
(Or will speed limits always be signed?)

5. How would a driver know that he is on an “institutional road” ? (45 mph)
(Or will speed limits always be signed?)

I am asking for each item whether these default limits will actually always be signed because of § 321.289 Speed signs — duty to install. I am not sure if that paragraph would apply to all of these. If it does, these default speed limits do only matter for the government and not for the drivers (and by extension, navigation systems, maps etc )

I dont think Iowa has used the “reasonable and proper” speed limit for a number of years.

2-lane highways in rural areas are almost always 55 mph. Interstates are 70 mph is rural areas, and 65 mph in suburban areas, and 55-60 mph in urban areas. Iowa seems to drop the speed limit from 70 mph to 65 mph much more readily than in other states; you basically just near a larger city and the speed limit is reduced. Four lane expressways (but not interstates) top out at 65 mph instead of 70 mph.

Hopefully this helps…

Thank you for your reply, Scott!

What I am specifically interested in is to find out the default speed limits, in other words, the speed limits that apply in the absence of speed limit signs. The Iowa law defines some statuary speed limits, see above(, but because of the article mentioned in the last paragraph of my last post,) I am not sure if they actually matter for the drivers (=drivers need to memorize these) or if they will **always **be signed limits in these cases.

**So, everything boiled down into one question: **Will the mentioned speed zones/districts/roads always have speed limits signs that indicate the effective speed limit? If not, is there any way (for a driver/surveyor) to know the effective speed limit by looking at the road features, the road classification/designation or even actual signs that inform him about that he is in a for example a suburban district, school zone or state park?

I read quite a few US legislations on statuary speed limits already, and many include special (low) speed limits on school zones. I understand, or well, my impression from what I have heard from you and various other people and seen on Google StreetView, is, that generally, across all of the USA, these school zones will always be signed and include a speed limit sign. This is why currently I leave out school zones from the mentioned Defualt Speed Limits wiki page, because the table only deals with roads where no speed limit is signed.

While I haven’t traveled extensively in Iowa, in my experience nearly all those cases will be signed except for rural areas. And even some rural areas may be signed as needed. Here are the general rules from the drivers manual

Appropriate Speed
The speed you can drive your vehicle depends on the
posted speed limit, the road conditions and the weather. The
faster your vehicle is going, the more distance it will take to
turn, slow or stop. For example, stopping at 60 mph does not
take twice the distance it takes at 30 mph as one might think,
but over three times the distance. The posted speed limit is
the FASTEST speed you can legally drive under ideal driving
conditions. The following general limits have been set:
• 20 mph in any business district;
• 25 mph in a residential district or school district;
• 45 mph in any suburban district, or for any vehicle
pulling another vehicle unless it was designed for
that purpose;
• 50 mph on unsurfaced secondary roads from sunset
until sunrise, and for all trucks on secondary roads
at any time of day;
• 55 mph on all primary roads, urban interstate highways
and secondary roads, including unpaved roads
from sunrise to sunset; and
• 70 mph on rural interstate highways.
A lower limit may be set for any conditions listed

And so, I guess, on those unsigned rural area roads, the speed limit would be 55 mph then?

There is a similar, or actually a far more complex case for Ohio where I begin to think that all the complexity in the law is actually aimed at the (gov) agencies who put the maxspeed signs up. See:

Yes, and that’s normally the only thing a driver would be expected to know that wouldn’t already be heavily signed.

Sorry, to ask again, but what about residential streets in residential zones / suburbia? Will really every single road be signed with 25 mph? Or is 25 mph assumed to be the default in residential areas so it is not (always) signed? (And what about business zones?)

That’s a good point about residential streets - normally these will only be signed as major streets lead into residential. But within the residential district, there may not be any more signs. I’m not sure about business zones having signs either. There are some cases where the ‘main street’ is perpendicular to main roads leading in, and may not be signed with a speed limit.