Highways with unusual milepost schemes

[adventurernumber1]

When the earlier portions of DE 1 first opened, the exit numbers were originally mile-marker based but then changed to kM-based exit numbers shortly thereafter.  IIRC, the highest exit number (near or at I-95) used to be just over 100; then it jumped to the 160s.

Hm. I didn't know that. But why would they change it to kilometers?

[PHLBOS]

When the earlier portions of DE 1 first opened, the exit numbers were originally mile-marker based but then changed to kM-based exit numbers shortly thereafter.  IIRC, the highest exit number (near or at I-95) used to be just over 100; then it jumped to the 160s.

Hm. I didn't know that. But why would they change it to kilometers?

There was a short-lived push in 1993-1994 nationwide to revive & implement the Metric System.  DelDOT probably thought changing the exit numbers on a new road before it was fully-completed was a cost-effective way to implement such.  When the push to Metric all but died in 1995; so did efforts to further implementing such on existing highways.

[formulanone]

Florida's Turnpike used to have exit numbers in multiples of four, with the zero point at I-95 near Miami. This left room for the addition of new interchanges, but it switched to a mileage-based system around 1989.

On the Homestead Extension, they used mileage-based exit numbers. My guess is that they standardized the mileage...but there's a four-mile spur from I-95 to the Extension between the two segments that's out of sequence, so they have weird mile markers.

[NE2]

Florida's Turnpike used to have exit numbers in multiples of four, with the zero point at I-95 near Miami. This left room for the addition of new interchanges, but it switched to a mileage-based system around 1989.

And multiples of 5 north of exit 60 (SR 60). http://en.wikipedia.org/wiki/Florida%27s_Turnpike#Exit_list has them listed.

But even earlier it used 1-12 without skipping, then skipped 2 or 3 per interchange to the end.

1964 map (10 not yet built)
1967 map (10 filled in and 23 I-4 added)

I'm not sure what exit numbers were used on the Homestead Extension, but my guess is that it standardized mileage (somewhat) between the two segments.

I don't think it had any until the change.

[Eth]

When the earlier portions of DE 1 first opened, the exit numbers were originally mile-marker based but then changed to kM-based exit numbers shortly thereafter.  IIRC, the highest exit number (near or at I-95) used to be just over 100; then it jumped to the 160s.

Hm. I didn't know that. But why would they change it to kilometers?

There was a short-lived push in 1993-1994 nationwide to revive & implement the Metric System.  DelDOT probably thought changing the exit numbers on a new road before it was fully-completed was a cost-effective way to implement such.  When the push to Metric all but died in 1995; so did efforts to further implementing such on existing highways.

This would also explain the kilometer posts present for a few years on US 431 in Alabama back in the mid-90s, especially since significant portions south of Phenix City had just been moved onto a new four-lane alignment anyway.

[froggie]

This would also explain the kilometer posts present for a few years on US 431 in Alabama back in the mid-90s, especially since significant portions south of Phenix City had just been moved onto a new four-lane alignment anyway.

As I recall, I-20/59 west of Birmingham had kilometer posts that survived into the early 2000s.

Regarding the topic, US 65 in Minnesota begins at Milepost 300 at the IA/MN line.  This is due to MN 65 (whose mileposts begin at zero).

The MN 62 in/near Minneapolis begins near MP 104.  This is for two reasons:  first, to avoid milepost duplication with the MN 62 near Windom, and secondly, the mileposts reflect mileage from Hennepin County's original plan (back when it was a county state-aid route) to loop 62 west and north to today's MN 7/CSAH 101 intersection in Minnetonka.

[DandyDan]

US 75's mileage in Iowa is still based on it beginning in Council Bluffs, which it hasn't done since 1982.

[roadman65]

No one here did mention that the Garden State Parkway in attempts to eliminate alphabet soup is one off on exit number to mileposts.  For example the 136 mile post is at Exit 135, the 124 milepost is at the Cheesquake Service Area south of Exit 123, and the 140 milepost is even two off as it is situated at Exit 138.

[PHLBOS]

No one here did mention that the Garden State Parkway in attempts to eliminate alphabet soup is one off on exit number to mileposts.  For example the 136 mile post is at Exit 135, the 124 milepost is at the Cheesquake Service Area south of Exit 123, and the 140 milepost is even two off as it is situated at Exit 138.

One reason for nobody mentioning the GSP would be that those listed oddities are too subtle to be noticed.

Truth be told, with the exception of your listed-Exit 138 at MM 140; your other two-listed examples of having a numeric difference of 1 between the nearest mile marker and the interchange is not unique to the GSP.  It's been done on other highways in other states as well.

[jeffandnicole]

No one here did mention that the Garden State Parkway in attempts to eliminate alphabet soup is one off on exit number to mileposts.  For example the 136 mile post is at Exit 135, the 124 milepost is at the Cheesquake Service Area south of Exit 123, and the 140 milepost is even two off as it is situated at Exit 138.

That's hardly unusual.

There's many exits in NJ that don't line up perfectly with their milepost #.

In Maryland, I-95's Exit 100 is located at approximately MP 99.6.

Exit 1 in many states is located below MP 1.

Besides, these aren't milepost scheme issues.

[roadman65]

No one here did mention that the Garden State Parkway in attempts to eliminate alphabet soup is one off on exit number to mileposts.  For example the 136 mile post is at Exit 135, the 124 milepost is at the Cheesquake Service Area south of Exit 123, and the 140 milepost is even two off as it is situated at Exit 138.

One reason for nobody mentioning the GSP would be that those listed oddities are too subtle to be noticed.

Truth be told, with the exception of your listed-Exit 138 at MM 140; your other two-listed examples of having a numeric difference of 1 between the nearest mile marker and the interchange is not unique to the GSP.  It's been done on other highways in other states as well.

Not if you are going the other way.  For example the Milepost 124 is located south of Exit 123 and not north of it.  The mile 99.6 for I-95 in MD is correct as its one half mile to the actual 100 milepost.  It normally goes to the nearest whole mile marker and usually in progression of how the numbers go.  Yes different states use different methods I will admit, but the GSP Parkway is most unique in this fashion.

In addition the GSP has in many places (look at the ACE cloverleaf) with Exit 38 and Exit 38A instead of Exit 38A & B like everybody else.  Then Exit 143 A and B  with A being north of B.  Letters too go from South to North like numbers do, and the same with Exit 4A being for NJ 47 North in Lower Township and Exit 4B being for NJ 47 South with the former being the first SB exit and the latter for the second.  Again they should be (and are not) reveresed.

[Pete from Boston]

Part of Mass. 2A is in smoots.

[formulanone]

When the earlier portions of DE 1 first opened, the exit numbers were originally mile-marker based but then changed to kM-based exit numbers shortly thereafter.  IIRC, the highest exit number (near or at I-95) used to be just over 100; then it jumped to the 160s.

Hm. I didn't know that. But why would they change it to kilometers?

There was a short-lived push in 1993-1994 nationwide to revive & implement the Metric System.  DelDOT probably thought changing the exit numbers on a new road before it was fully-completed was a cost-effective way to implement such.  When the push to Metric all but died in 1995; so did efforts to further implementing such on existing highways.

This would also explain the kilometer posts present for a few years on US 431 in Alabama back in the mid-90s, especially since significant portions south of Phenix City had just been moved onto a new four-lane alignment anyway.

I've seen a few scattered kilometer posts in Alabama, one on US 29 northeast of Troy and another along AL 17 somewhere south of I-20. They seemed to be placed quite far off to the extreme ROW limits, as if on purpose.

[Brandon]

No one here did mention that the Garden State Parkway in attempts to eliminate alphabet soup is one off on exit number to mileposts.  For example the 136 mile post is at Exit 135, the 124 milepost is at the Cheesquake Service Area south of Exit 123, and the 140 milepost is even two off as it is situated at Exit 138.

That's hardly unusual.

There's many exits in NJ that don't line up perfectly with their milepost #.

In Maryland, I-95's Exit 100 is located at approximately MP 99.6.

Exit 1 in many states is located below MP 1.

Besides, these aren't milepost scheme issues.

No, that's just a fear of the number zero.

Zerophobia?

[lordsutch]

I've seen a few scattered kilometer posts in Alabama, one on US 29 northeast of Troy and another along AL 17 somewhere south of I-20. They seemed to be placed quite far off to the extreme ROW limits, as if on purpose.

Alabama was one of the few states to actually make some progress on metrication; the guide signs on the original US 78/I-22 Jasper bypass section (from current AL 118 to AL 269) were originally signed using metric distances and exit numbers, but have since been patched over or replaced. See e.g. http://www.lordsutch.com/roads/us78/newer/6.html

[roadman]

MA 128 has a "secret" set of mileposts between Canton and Peabody where it runs concurrent with I-95 - the posted mileposts reflect the I-95 mileage.  This is why, when 128 separates from I-95, the first milepost you see reads 37.2 instead of 0.2.

[roadman65]

FL 429 to avoid the zero factor has Exit 1 for its southern terminus, but Exit 1A at th7e first exit close to actual MM 1.

Some places like NJ and IL uses the other interstate's numbering scheme to avoid this hence Exit 60 on I-195 and NJ 29 at their zero ends.  Also I-24 western terminus uses I-57's mileage for both the I-57 exit to I-24 and from I-24 to both ramps to I-57.

[hbelkins]

Aren't there some funky mile markers on I-40 just inside the Tennessee state line in Memphis?

[tdindy88]

I seem to remember the exits were...a bit off the last I was there. Probably something to do with the rerouting of I-40 around Memphis' north side. As I recall, the I-40 exit with I-240 and Sam Cooper were marked Exit 12, and then the exit to the east of I-240 along I-40 was also Exit 12. I don't remember the mile markers around there but this is odd. Again, I'm sure the reason is for the rerouting.

[PHLBOS]

MA 128 has a "secret" set of mileposts between Canton and Peabody where it runs concurrent with I-95 - the posted mileposts reflect the I-95 mileage.  This is why, when 128 separates from I-95, the first milepost you see reads 37.2 instead of 0.2.

For a few years during the 80s, when the DPW posted mile-marker placards on overpass/underpass structures that showed to the second decimal place (100ths) it was based on Mile 0 along 128 being located near/at the Exit 44B (old 30B) ramp for US 1 North and increasing north/eastward.  Some of which still remain to this day.  I'm not sure if the stand-alone mile markers along that stretch of 128 ever reflected such.

Overpass mile marker 3.71 along MA 128 southbound at the MA 114 interchange (Exits 25A-B) vs. MM 39.8 located just northeast of the MA 114 overpass

I'm even more surprised that those (the structure MM placards) weren't reset when the I-95 North interchange was finally completed a few short years later or weren't set up that way (0 at the then-theoretic I-95 North break-off) when I-95 was re-routed onto most of 128.  The interchange and ramp layout were on paper years before ground was actually broken to build it.

Had MM 0 for 128 been reset at where I-95 breaks off/merges; then the fore-mentioned MM 39.8 near MA 114 would be MM 2.7-2.8* (the overpass placard would be MM 2.6 or 2.7*-something). 

*IMHO, the current 128 MM 37.2 would actually be unsigned MM 0.1 if MM 0 were set at the fore-mentioned location.

One could recite what the mile-marker-based 128 interchanges from Peabody to Gloucester would/should be; but that's another topic for another thread.

[Brandon]

FL 429 to avoid the zero factor has Exit 1 for its southern terminus, but Exit 1A at th7e first exit close to actual MM 1.

Some places like NJ and IL uses the other interstate's numbering scheme to avoid this hence Exit 60 on I-195 and NJ 29 at their zero ends.  Also I-24 western terminus uses I-57's mileage for both the I-57 exit to I-24 and from I-24 to both ramps to I-57.

Not always.  I-24's end is an oddity in Illinois.  Other interstates and freeways have an Exit 0.  I-474/IL-6 share an Exit 0, marked as Exits A and B.  I-355, I-155, and I-172 have an Exit 0 as well.  I-290's ends lack exit numbers, as does I-39's south end.  IL-255 uses I-255's exit number (30).  I-88 uses Exit 1.  I-180 does not have exit numbers.  I-294 uses I-80's exit number westbound (160), but it is concurrent with I-80 at that point; but lacks an exit number eastbound.  That may change when the Tri-State Tollway gets exit numbers.  I-190 just merges into I-90 inbound.

I-355 (not on GSV yet):

[Scott5114]

Bit of trivia:  in its documentation, TxDOT uses US 82 across Texas as an example of the reference marker system in operation.  Lowest marker value is 220 at the Yoakum County line (western edge of the Texas Panhandle) and highest marker value is 798 in Texarkana.  This is a difference of 578 miles.  However, Google Maps gives the length of US 82 across Texas as 565 miles.  Where did the extra 13 miles go?

(Edit--Wxfree's post, which came through as I was composing this one, offers a possible explanation for the 13-mile discrepancy.)

The usual reason for milepost discrepancies like this is concurrencies having their mileposts measured along the other route, but that would seem to not be the case here, since extra mileage is accrued. Another option could be a realignment. wxfree's idea is also a possibility.

[hbelkins]

Aren't there some funky mile markers on I-40 just inside the Tennessee state line in Memphis?

Found some of my photos:

[swbrotha100]

As someone already mentioned, many numbered highways in Arizona carry over the mileage sequence from when two numbered highways branch off. I-17 inherited its numbering from when AZ 69 used to come into Phoenix.

Currently US 93 starts at zero at the Nevada border, and numbers increase as you go south.

[Milepost61]

Most of Wyoming's non-Interstates (particularly the US highways) have oddball mileposting, because the mileposts are done relative to maintenance control route numbers, not the signed highway numbers.