AARoads Forum

Regional Boards => Northwest => Topic started by: KEK Inc. on April 12, 2021, 04:00:40 PM

Title: Oregon Z mile markers
Post by: KEK Inc. on April 12, 2021, 04:00:40 PM
After getting my second vaccine dose, why not drive 5 hours from Seattle and go camping on the Oregon coast?! 

I noticed near Tillamook there were mile markers with Z prefixing the number on US-101.


iPhone
Title: Re: Oregon Z mile markers
Post by: Alps on April 12, 2021, 06:16:09 PM
Probably rerouted.
Title: Re: Oregon Z mile markers
Post by: Road Hog on April 13, 2021, 07:08:30 PM
Zombie evacuation route?
Title: Re: Oregon Z mile markers
Post by: Bickendan on April 13, 2021, 11:54:28 PM
I need pictures of these Zombie Evacuation Route/Highway, er, reroute markers!
Title: Re: Oregon Z mile markers
Post by: JasonOfORoads on April 15, 2021, 01:16:03 PM
After getting my second vaccine dose, why not drive 5 hours from Seattle and go camping on the Oregon coast?! 

I noticed near Tillamook there were mile markers with Z prefixing the number on US-101.


iPhone

This is what ODOT uses for overlapping mileage on a highway. Usually this comes about from a rerouting that is slightly longer than its original routing. However, this is a unique case that comes from the cancellation of a highway project.

Originally, the Oregon Coast Highway was planned to travel due south from Manzanita (near the intersection of US-101 and Laneda Ave., to be specific), travel down the sand spit between the ocean and the Nehalem River, cross the river, and reconnect at 101 near Nedona Beach. While waiting for it to be built, the Oregon State Highway Department designated 101 down the routing it's on today. It was considered a "temporary travelled route" because at the time, the road was a Tillamook County road from Manzanita through Nehalem to the junction of OR-53; south of there, 101 was routed along the Necanicum Highway to the Nedona Beach area. Once the new road was constructed, 101 would have been removed from the temporary routing; the northern portion would've reverted to a Tillamook County road, and the southern portion would've been an extension of OR-53.

(https://photos.smugmug.com/MAPS/Road-maps/i-hx6qWvn/0/445b3cc4/X2/1970%20Hwy%20101%20route-X2.jpg)

However, with the rise of conservation efforts in the 1960s, the Nehalem sand spit route (as well as another rerouting of 101 further south near Tierra Del Mar/Pacific City) underwent a lot of scrutiny, so much so that it impacted gubernatorial politics. Long story short, environmental and erosion concerns won out, and the sand spit route wasn't consturcted. By 1972 (IIRC), the highway department negotiated with Tillamook County to take over jurisdiction of the northern portion of "temporary" 101, making it officially part of the Oregon Coast Highway and 101. The southern portion simply needed the highway commission to redesignate it as part of the Oregon Coast Highway, which was done at the same time. Instead of re-mileposting 300+ miles of Oregon Coast Highway and updating thousands of records just to make the mileage accurate, they opted to create about 4.5 miles of Z-mileage along that corridor, hence why we see the duplicate mileage today.

As for the sand spit, it became an Oregon State Park around 1972 to further protect it from development.
Title: Re: Oregon Z mile markers
Post by: The Ghostbuster on April 15, 2021, 09:00:08 PM
Z mile markers are a unique occurrence, no?
Title: Re: Oregon Z mile markers
Post by: JasonOfORoads on April 15, 2021, 10:50:34 PM
Z mile markers are a unique occurrence, no?

Yeah, the mile markers are pretty rare. Most Z-mileage isn't very long and is hidden in the field. The only other Z-mileage I can think of that's of any significant length is along OR-27, after it was rerouted when the Prineville Reservoir was built. However, most of that route is unpaved, and IIRC there aren't any mileposts along that section; last I checked, ODOT's highway inventory data states that the mileposts are "missing", but they may have never been placed in the first place. ODOT had no real choice but to post the ones along US-101, since it is a heavily-travelled highway.
Title: Re: Oregon Z mile markers
Post by: KEK Inc. on April 19, 2021, 01:48:58 PM
I was driving and my friend I was with doesn't care about roads, so I couldn't snap a picture.  lol

Here is one I passed that's on Google Maps:
https://www.google.com/maps/@45.6788383,-123.9238746,3a,50.3y,211h,88.18t/data=!3m6!1e1!3m4!1sux6b4Mt4kbl7WiPgy0frPQ!2e0!7i13312!8i6656

That explanation makes sense Jason.  Thanks!
Title: Re: Oregon Z mile markers
Post by: rarnold on April 19, 2021, 10:12:28 PM
So are these Z mile markers akin to Iowa using ahead and back markers when a route is shortened or lengthened?
Title: Re: Oregon Z mile markers
Post by: JasonOfORoads on April 20, 2021, 01:32:06 PM
So are these Z mile markers akin to Iowa using ahead and back markers when a route is shortened or lengthened?

Sorta, yeah. They are definitely the results of ahead/back equations in the underlying milepost data, but I've never seen a marker that denotes the BK=AH at the specific spot the equation occurs. It's similar to "B"-mileage that WSDOT uses on lengthened routes.
Title: Re: Oregon Z mile markers
Post by: roadman65 on July 08, 2021, 01:08:45 PM
Also the mileposts in Oregon are in reverse along US 101 as they start at the Astoria- Megler Bridge and go up to the California line.  Ditto for US 199 as they progress to California from OR 99 in Grants Pass and US 30 is even more odd. It starts from Portland to the foot of the Astoria- Megler Bridge.
Title: Re: Oregon Z mile markers
Post by: Bickendan on July 08, 2021, 03:18:06 PM
I-5, US 30, OR 35, I-205, and I-405 are the exceptions.
0 points are the Columbia River and the Pacific Ocean.

OR 35's is at OR 99W on US 26.
Title: Re: Oregon Z mile markers
Post by: roadman65 on August 01, 2021, 10:49:04 PM
Why is US 30 backwards? Itís zero is in Portland at I-405 and climbs up to Astoria instead of the other way around.
Title: Re: Oregon Z mile markers
Post by: BigManFromAFRICA88 on August 03, 2021, 10:16:59 PM
I-5, US 30, OR 35, I-205, and I-405 are the exceptions.
0 points are the Columbia River and the Pacific Ocean.

OR 35's is at OR 99W on US 26.
The funny thing is I was going to ask about these reverse mile markers on US 101 and US 30 after a trip up the Oregon coast and into Portland. Jarring as a road geek crossing the California line and seeing a milepost in the 360s haha
Title: Re: Oregon Z mile markers
Post by: JasonOfORoads on August 18, 2021, 04:26:22 AM
Why is US 30 backwards? It’s zero is in Portland at I-405 and climbs up to Astoria instead of the other way around.

It's because the two major highways in the 1910s, the Pacific Highway and Columbia River Highway, both based their zero mileposts in Portland when they were originally built. These are still held over today in the mileposts for highways 2, 2W, 1E and 1W (well, before a lot of it got transferred back to Portland). For 1E and 1W, this used to be entered into ODOT's records as "X-mileage" and referenced on straightline charts and other documents as such. For example, MP X1.00 would be one mile north of the zero milepost in Portland to distinguish it from MP 1.00 one mile south of Portland. However, ODOT upgraded their systems sometime in the 2000s to allow for negative milepost values, so MP X1.00 became MP -1.00. ODOT split off 2W from 2 at some point in the mid-1950s; I imagine this was to avoid having a highway on their books with 100 miles of X-mileage, but they kept the original milepost values for ease of recordkeeping.