Mileage-based exits and road extensions

[Roadgeekteen]

Today my mom asked me what would happen with the exit numbers if a road is extended. What do states do if a road is extended west or south?

[ilpt4u]

Today my mom asked me what would happen with the exit numbers if a road is extended. What do states do if a road is extended west or south?

If you are I-69 in Indiana, the existing 465 to Michigan section simply gets a +200 to their existing number. Who cares if it is accurate?!?

[SkyPesos]

For I-69 in Indiana, the exit numbers in the existing section got renumbered by adding 200 to the old exit numbers north of I-465, which lessens confusion, but is 16 miles over the 184 miles of I-69 between that point and the KY border in Evansville. Some other extensions renumbered exits to be exact based on how it is today (examples like I-70 CO west of Denver or I-75 FL south of Tampa).

[Roadgeekteen]

Today my mom asked me what would happen with the exit numbers if a road is extended. What do states do if a road is extended west or south?

If you are I-69 in Indiana, the existing 465 to Michigan section simply gets a +200 to their existing number. Who cares if it is accurate?!?

That's not going to be fun when the whole route is complete.

[SkyPesos]

Today my mom asked me what would happen with the exit numbers if a road is extended. What do states do if a road is extended west or south?

If you are I-69 in Indiana, the existing 465 to Michigan section simply gets a +200 to their existing number. Who cares if it is accurate?!?

That's not going to be fun when the whole route is complete.

The extra mileage is hidden in the I-465 concurrency. The proposed exit number for the southern I-69 interchange with I-465 is 163. Average drivers continuing north on 69 past the 465 concurrency won't notice that the exit numbers are larger than they should be.

[ran4sh]

For I-69 in Indiana, the exit numbers in the existing section got renumbered by adding 200 to the old exit numbers north of I-465, which lessens confusion, but is 16 miles over the 184 miles of I-69 between that point and the KY border in Evansville. Some other extensions renumbered exits to be exact based on how it is today (examples like I-70 CO west of Denver or I-75 FL south of Tampa).

Idk about CO, but for FL they were using sequential exits when I-75 was extended. The conversion to mile marker exits only occurred about 2 decades ago.

For the OP, another example is I-26 in NC, when it was extended "west" of Asheville the existing section was renumbered according to the new mile markers.

Today my mom asked me what would happen with the exit numbers if a road is extended. What do states do if a road is extended west or south?

If you are I-69 in Indiana, the existing 465 to Michigan section simply gets a +200 to their existing number. Who cares if it is accurate?!?

That's not going to be fun when the whole route is complete.

The extra mileage is hidden in the I-465 concurrency. The proposed exit number for the southern I-69 interchange with I-465 is 163. Average drivers continuing north on 69 past the 465 concurrency won't notice that the exit numbers are larger than they should be.

That's true, although the MUTCD calls for the mileage to continue being counted within a concurrency so that drivers' odometer readings will be consistent with the exit numbers.

But in that specific case I agree that adding 200 was the least confusing thing to do. I would even suggest that the new part of I-69 could have just been renumbered based on the 200 mile marker for the original section, which I think is more important than having the state line be exactly mile 0.

[ilpt4u]

When ISTHA extended I-355 south, well exit numbers didn't exist on the ISTHA Tollways, and the original mileage posted was MM 13.5 at the I-55 interchange, basically because the Will County extension was always part of the plan

We'll have a real life example in the next decade, with the Missouri I-57 extension from Sikeston to the Arkansas border

[Roadgeekteen]

When ISTHA extended I-355 south, well exit numbers didn't exist on the ISTHA Tollways, and the original mileage posted was MM 13.5 at the I-55 interchange, basically because the Will County extension was always part of the plan

We'll have a real life example in the next decade, with the Missouri I-57 extension from Sikeston to the Arkansas border

That is only a couple of exits.

[webny99]

I believe states are supposed to factor in any potential southbound or westbound extensions when setting exit numbers. It might not be exact if the exact routing changes, but it should be within one or two miles in most cases.

[ilpt4u]

For another 3DI example, you get a Max Mileage collision at the border on I-265 around Louisville. Indiana's mileage counts Clockwise and Kentucky's mileage counts Counterclockwise, since the East End/Lewis & Clark Bridge opened and connected the two I-265s

[SkyPesos]

Today my mom asked me what would happen with the exit numbers if a road is extended. What do states do if a road is extended west or south?

If you are I-69 in Indiana, the existing 465 to Michigan section simply gets a +200 to their existing number. Who cares if it is accurate?!?

That's not going to be fun when the whole route is complete.

The extra mileage is hidden in the I-465 concurrency. The proposed exit number for the southern I-69 interchange with I-465 is 163. Average drivers continuing north on 69 past the 465 concurrency won't notice that the exit numbers are larger than they should be.

That's true, although the MUTCD calls for the mileage to continue being counted within a concurrency so that drivers' odometer readings will be consistent with the exit numbers.

But in that specific case I agree that adding 200 was the least confusing thing to do. I would even suggest that the new part of I-69 could have just been renumbered based on the 200 mile marker for the original section, which I think is more important than having the state line be exactly mile 0.

I'm not opposed to the idea of hiding extra mileage at a southern/western terminus or a state line. Some interstates already do that (looking at the imaginary first 194 miles of I-17). Depending on where the I-69 Ohio River bridge would be based on the maps of the two alternatives, under that scenario, I-69 would either start at MM 15 (if at same location of the US 41 bridge) or 16 (if at a new location about a mile to the east) at the KY-IN border.

[Big John]

When WI 15 was changed to I-43, those numbers stayed the same while the exit numbers on the original I-43 segment increased by 72 or 73 to get exact mileage accounting for the new section.

[bassoon1986]

I-49 in Louisiana will be a hefty remembering if and when the full extension from Lafayette to New Orleans occurs.


iPhone

[OCGuy81]

When WI 15 was changed to I-43, those numbers stayed the same while the exit numbers on the original I-43 segment increased by 72 or 73 to get exact mileage accounting for the new section.

When 41 was given interstate status, was there mile markers along the corridor prior to it being an interstate?  If so, were those changed to reflect the routing along 43/894?

[Big John]

When WI 15 was changed to I-43, those numbers stayed the same while the exit numbers on the original I-43 segment increased by 72 or 73 to get exact mileage accounting for the new section.

When 41 was given interstate status, was there mile markers along the corridor prior to it being an interstate?  If so, were those changed to reflect the routing along 43/894?

No, they were kept the same.

[SkyPesos]

Seems like US 41 wasn't even on the mile markers on the Zoo Freeway section at all, even before I-41.
US 45 mile marker (pre I-41)
I-41 mile marker