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Mile Marker Accuracy

Started by twowheeler, March 29, 2018, 10:43:05 PM

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Bickendan

Quote from: roadman65 on March 31, 2018, 04:53:45 AM
How does roads like I-84 in OR or I-24 in TN where both carriageways shift miles apart?  One side has got to be longer than the other, so how does both Oregon and Tennessee compensate?
I-84 is inaccurate even without factoring Emigrant Hill because of the Mt Hood Frwy's demise.


cbeach40

Tangentially related, but for a recent reconstruction of ON-3 on the St. Thomas Expwy we encountered a problem with our chainage. Basically, the highway is built as a staged freeway, with bi-directional traffic on what is to ultimately be the eastbound lanes. However, the chainage is based on the centreline of the ultimate configuration. So as we went through the project, the difference between the ultimate centreline and the centreline of the existing lanes had greater and greater variation. So for construction purposes we actually created a project-specific set of stations that reflected the offset lanes from the ultimate centreline.

and waterrrrrrr!

roadfro

Quote from: Beltway on April 24, 2018, 02:35:25 PM
On a section with a graded median they could use the centerline of the original design plans in the center of the median.

With a section with independantly graded roadways, the design plans would have a separate centerline for each roadway.  That would be more complex, but for the sake of mileposting the survey party could establish a temporary centerline halfway between the two roadways and then base the mileposting from that.

I've seen project plans where there is an overall highway centerline, and each carriageway also has a separate centerline shown for construction stationing purposes.
Roadfro - AARoads Pacific Southwest moderator since 2010, Nevada roadgeek since 1983.

Scott5114

Quote from: twowheeler on March 29, 2018, 10:43:05 PM
I've made a doohickey that looks at the rotation ratio between front and back wheels of a bicycle. I can readily detect a 20 psi deficit in one tire. Pressing a button at two successive mile markers allows an independent pressure reading for each tire, but the mile markers need to be consistent within 5 feet for good results.

Maybe I'm not quite understanding the project correctly, but if you're tracking tire rotation, wouldn't it be easier to take the diameter of the tire and how many times it rotates to calculate the distance traveled, rather than rely on manual input of something external like mile markers?
uncontrollable freak sardine salad chef

Flint1979

I know Michigan's are pretty good. Each time I've ever tried to test the distance of them I've made the 80 mph to a mile in 45 seconds which is what it's suppose to be.

SSR_317

Quote from: ftballfan on April 23, 2018, 09:49:45 PM
I-75 in Ohio has some exit numbers that are one off their mile markers.
I have seen that different states handle rounding in different manners for purposes of interchange (exit) number assignments. At also differing about how to select the exact point that defines the whole interchange (e.g. using the point where the centerlines intersect versus the first actual gore point in the increasing reference post direction). And then there's the whole issue of the MUTCD not recognizing the need for an Exit 0...  what are they at AASHTO, a bunch of Romans with no concept of zero?

US 89

Quote from: Scott5114 on April 25, 2018, 11:00:36 PM
Quote from: twowheeler on March 29, 2018, 10:43:05 PM
I've made a doohickey that looks at the rotation ratio between front and back wheels of a bicycle. I can readily detect a 20 psi deficit in one tire. Pressing a button at two successive mile markers allows an independent pressure reading for each tire, but the mile markers need to be consistent within 5 feet for good results.

Maybe I'm not quite understanding the project correctly, but if you're tracking tire rotation, wouldn't it be easier to take the diameter of the tire and how many times it rotates to calculate the distance traveled, rather than rely on manual input of something external like mile markers?

The way I understand it, a lower tire pressure decreases the diameter of the tire. Having an external mile marker provides a reference for how many rotations equal a mile for each tire. If the difference in that number between the two tires is significant, their pressures would be significantly different.

ErmineNotyours

Quote from: Super Mateo on March 31, 2018, 04:19:11 PM
What happens in a situation like this?  Eastbound I-80 takes a loop ramp to continue its route.  Is the mileage measured on the ramp?

In Washington State, when a highway connects to itself through an interchange, the mileage connects to itself where it crosses over/under a bridge.  See Historical Alignment Note here: http://www.wsdot.wa.gov/mapsdata/tools/InterchangeViewer/pdf/SR007/007X057.pdf

I noticed recently the mileposts for SR 181 has shifted a few feet north and the state has posted new mileposts reflecting this.  I'll have to get out there and take pictures.

ErmineNotyours

A few months ago I noticed that the state had moved this marker about 10 feet north, from the pole on the right to the other side of the bus shelter.  The marker across the street also moved the same distance.  All along WA SR 181 new mileposts have gone up; you can tell they are new posts because of the pre-drilled holes.  I'm not as familiar with the old post locations elsewhere on this road to know how far they moved.  It's not as if the south end of the route was cut off by 10 feet.  The road has begun at Mile 5.32 since the state cut off the rest in 1992.  181 is the only branch number of SR 18, and it doesn't even touch that highway any more.  On the other hand, there are several 16x's that do touch 18, but don't come close to 16.  Go figure.

The state's official highway log says not to use the mile posts for computing distances (page 11) but that could be due to "equations" resulting from the length of the roadway changing.

Milepost moved 10 feet, from the pole on the right by Arthur Allen, on Flickr

ErmineNotyours

This morning, ten hours after I posted the above picture that includes a graffiti-covered bus stop sign, workers were replacing it with a new one.  Coincidence?  There could be local transit workers who read this site.

amroad17

Quote from: ftballfan on April 23, 2018, 09:49:45 PM
I-75 in Ohio has some exit numbers that are one off their mile markers.
Ohio generally has their exit numbers correspond to the closest milemarker (reference marker) south or west to the centerline point at the interchange.  Using I-74 as an example, the mile 8 sign is located just to the east of the overpass over OH 128, still within the interchange ramps.  In Ohio (and Virginia), this interchange is Exit 7.  In many other states (Kentucky, Indiana, and Pennsylvania for example) this would be considered as Exit 8.  This "rule" is sometimes broken in Ohio (examples are Exit 75 on I-71, the 75 mm sign is just past the OH 38 overpass; Exit 204 on I-71, same example as Exit 75). 
In your statement above, I do remember one interchange where the exit number is one off.  It is Exit 74 (OH 41) on I-75 in Troy.
Looking at Google Maps, I see the 75 mm is posted between the northbound off-ramp and the OH 41 overpass.  This should have been Exit 75 and not Exit 74.  Maybe it was assigned Exit 74 so one would not have to hear, "Get off at Exit 75 on 75."  Maybe it was to avoid potential confusion.
Overall, it depends on each states' DOT's how they want to assign each interchange's exit numbers.
I don't need a GPS.  I AM the GPS! (for family and friends)



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