Illinois: Round Mile Markers, Interpretations and Misinterpretations

[Rothman]

About two-and-a-half months ago, I got into a discussion about alleged "hidden routes" in Illinois somewhere out there on the Interwebs.  Turns out that some people think that markers like this:



can indicate "hidden state routes."

To confirm their suspicions, I reached out to IDOT and asked about the markers and why they have route numbers on them that may not be signed or have routes in IROADS. I referenced a specific example where one of these markers indicated a route 316 where the IROADS indicated it did not exist.  I got a response from their Operations group:

"While the route near Charleston is not officially designated as state route 316, this is what our local IDOT district and residents in the area refer to the road as, so 316 was chosen for display on the reference signs."

Therefore, one should not use such markers as reliable indicators of official Illinois state routes.

[NE2]

If the local IDOT district refers to it as 316, does that not make it at least semi-official?

[74/171FAN]

So IL 905 is still a thing right off of I-474??  (https://www.facebook.com/photo/?fbid=10219520080833154&set=a.10219520161635174)



Exit being referenced to:

[adt1982]

The thing about 316 is that the road actually was marked as IL 316 from 1963 to 1981.

Here in Montgomery County, old US 66 is marked with those signs as 934.

[vdeane]

If the local IDOT district refers to it as 316, does that not make it at least semi-official?

By that logic, NY 7 from I-87 to Troy is actually Alternate NY 7.  And an interstate.

[ilpt4u]

Part of me wants to go knock on the door at IDOT D9 in Carbondale and ask someone on staff if that is accurate. I only see those route/county/mileage reference markers on state maintained roads, whether a shielded highway, old shielded highway, or merely "other" state-maintained routes

Business Highway 13 between IL 149/Walnut and IL 13/127 north of town (follows 11th St north from 149, becomes west on Poplar St, turns north on 14th St, then turns northeast on Ava Rd to reach 13/127) in Murphysboro doesn't have the reference markers at all, but it is IDOT-maintained

That said, D9 is at least decent signing "Begin State Maintenance" and "End State Maintenance" on state-maintained non-shielded roads

[Rothman]

Part of me wants to go knock on the door at IDOT D9 in Carbondale and ask someone on staff if that is accurate. I only see those route/county/mileage reference markers on state maintained roads, whether a shielded highway, old shielded highway, or merely "other" state-maintained routes

Business Highway 13 between IL 149/Walnut and IL 13/127 north of town (follows 11th St north from 149, becomes west on Poplar St, turns north on 14th St, then turns northeast on Ava Rd to reach 13/127) in Murphysboro doesn't have the reference markers at all, but it is IDOT-maintained

That said, D9 is at least decent signing "Begin State Maintenance" and "End State Maintenance" on state-maintained non-shielded roads

State maintained =/= state route.

[ilpt4u]

That is a fine delineation. But for all practical purposes, when state maintained, it at least acts and quacks like a shielded/designated state route

[Rothman]

That is a fine delineation. But for all practical purposes, when state maintained, it at least acts and quacks like a shielded/designated state route

Not really.  You have to define the route for there to be a route.

[ilpt4u]

That is a fine delineation. But for all practical purposes, when state maintained, it at least acts and quacks like a shielded/designated state route

Not really.  You have to define the route for there to be a route.

I was referring more to things like state ROW and permitting requirements, obviously state maintenance, state law enforcement, etc

For navigational and routing purposes, certainly not. Designated/signed routes are such for a reason, even if we sometimes find them ridiculous (the 100% redundant IL 110/336 designation). Unsigned/state-maintained routes are not typically the "major" corridor, more for local and/or business access or "old"/former alignments of realigned highways

[paulthemapguy]

State maintained =/= state route.

Wat.

It's state-maintained and it's a route. It's a state route.  It may not be a State Route, but it's a state route. The adjective "state" and the noun "route" are both correct.

IDOT maintains plenty of roads that are not signed routes. Besides signed numerical designations, there is a separate internal set of numerical designations for various roads across Illinois, state-maintained and otherwise (shown as "FAP", "FAU", etc.). But I don't think that's even what appears at the top of these mile markers.  The process of deciding these numbers for the top of these mile markers has always been a mystery to me. Such numbers are usually in the 8000s or 900s (though 316 is an oddball).

Bill Burmaster's (rmsandw) site has covered a plethora of these unsigned state highways: https://www.billburmaster.com/rmsandw/illinois/misc/il900.html

Here are a few I have found in the wild:


IL-8677 by Paul Across America, on Flickr


IL-905WR-I-474 by Paul Across America, on Flickr


IL-911-0MI by Paul Across America, on Flickr


IL-919 by Paul Across America, on Flickr

[Rothman]

State maintained =/= state route.

Wat.

It's state-maintained and it's a route. It's a state route.  It may not be a State Route, but it's a state route. The adjective "state" and the noun "route" are both correct.

IDOT maintains plenty of roads that are not signed routes. Besides signed numerical designations, there is a separate internal set of numerical designations for various roads across Illinois, state-maintained and otherwise (shown as "FAP", "FAU", etc.). But I don't think that's even what appears at the top of these mile markers.  The process of deciding these numbers for the top of these mile markers has always been a mystery to me. Such numbers are usually in the 8000s or 900s (though 316 is an oddball).

Bill Burmaster's (rmsandw) site has covered a plethora of these unsigned state highways: https://www.billburmaster.com/rmsandw/illinois/misc/il900.html

Re-read the OP and understand where this thread started. You could also see what IDOT told me about where one fun marker came from as well (the 316 markers near Charleston on a segment that is not route 316).  So, yeah, the "route numbers" on the markers should not be trusted for the actual route designation, like I said at the beginning.

Regarding the top number on the marker, my new friend at IDOT says, "If the route is unmarked, then an alternate or arbitrarily assigned 900-series number is used."  In other words, the numbers on the markers are made up and have no correlation to any route designation and are -- to-many-a-roadgeek's-horror -- arbitrary.

Regarding the separate designations that you brought up: "Inventory Key Route" is an interesting designation, but it fulfills a specific purpose:  This route designation is mainly to help with functional class of segments and therefore funding eligibility.  This designation is simply for the compiling of their 5-year [functional] classification maps.  Hence, "FAP" is federal-aid primary, "FAI" is federal-aid interstate, "FAU" is federal-aid urban, and so on, down to "Local" (classified by FHWA as not fed-aid eligible -- not by ownership or maintenance responsibility!).  So, Inventory Key Routes are definitely not what we think of when we think of "State Routes," as you put it.  They're not even "hidden State Routes," so to speak (i.e., State Routes IDOT just didn't shield for whatever reason).

Furthermore, what else is fun is "Marked Routes" -- the "State Routes" we know and love -- are not an exclusive set of route designations.  In other words, all Marked Routes have Inventory Key Route numbering -- well, of course, because all roads have a functional classification.  But not all Inventory Key Routes are Marked Routes.  So, it's not one or the other.  But, Marked Routes are the "State Routes," as you put it, whether actually shielded or not.

So, no, state-maintained does not mean that it's on a State Route, and just because it has an Inventory Key Route doesn't mean that it's on a "hidden State Route" and I would go as far to say not even a real "state route," since you're talking about a GIS programmer's palette, essentially in that dataset.

In any matter, I find IDOT's practices to be overly convoluted in this matter...and actually not well-perceived.  My new friend at IDOT says that the round markers are used to identify crash locations, but if they don't correlate to anything official in their easily available GIS applications or, worse, only in one esoteric GIS database somewhere that keeps track of such, how efficient is that practice?  I mean, NYSDOT has a lot of obsolete reference markers out in the field, but at least you can say that they were actually from a former designation rather than just "arbitrarily" numbered!  And, I believe by now, NYSDOT finally has all their GIS data at least in one spot so its Regions don't need their own tailored ArcGIS files...IDOT's hodgepodge is looking behind the times.  And, fine, NYSDOT does have various ways of inventorying its roads, but at least when you're talking about route numbers, reference markers and milepoints it all makes sense (except for the ye olde hyphenated route designations that are used to look up ye olde record plans from the medieval ages).

But wait, there's a postscript to this rant -- a codicil, if you will: Although I respect roadgeeks like Bill that dig into what-I'll-call "artifacts" -- old maps, old shields in the field, heck, old DOT docs -- to find out how DOTs operate, there's a lot of speculation or assumptions made out there based on such reading of the tea leaves that are incorrect and found to be such just by sending a DOT an e-mail and eventually getting an actual response.