Mileage Based Exits coming to CT

[roadman]

The "dual numbering" system ("MILE XX, EXIT YY") was actually promoted by BPR/FHWA and was used by a number of states in the late 1960s and early 1970s.  Both Massachusetts and Rhode Island had dual numbering on some of their Interstates for awhile.

[agentsteel53]

interesting that you should note California's small postmile paddles.  not only are they tiny and inconspicuous, they also have their origin at a county line - rendering them pretty damn useless in many situations.

I remember attempting to find an old US-60/70 alignment on I-10, and my map showed that road as Chuckwalla Valley Road, exit 201.  I missed the exit because

a) the postmiles were in the 70s or so.

b) the exit name was Corn Springs Road, which - while technically present in that area - was not the actual road being branched, and also is a road which is significantly less important.

c) California wasn't using exit numbers.  at all. 

since the next exit is 17 miles down the road, that's how I ended up detouring 34 miles out of my way.  I'm not sure how Caltrans intended for me to find the correct exit given all three of these things stacked against me.

[vdeane]

what was the advantage of sequential exits, that everyone adopted it back in the day?

This is just speculation on my part, but here is what I think:

*  Many state DOTs began numbering exits long before they reached substantial completion even of their rural Interstate mileage.  It was easier to count access points than to guess mileage along route segments for which a corridor had been approved but a line had not actually been surveyed on the ground.

*  Many state DOTs conceived of the Interstates (for which exit numbering was first introduced) primarily as a rural highway program, and failed to anticipate the demand for new access points that would result from suburbanization promoted by the Interstates.  Added access points interfere with sequential numbering schemes because they have to be dealt with through letter suffixes or through complete revamp of the sequential numbering scheme.

*  The turnpikes, which were the first rural freeways and the forerunners of the Interstates, uniformly had sequential exit numbering.  Sequential numbering was therefore the incumbent standard and there would have seemed to most state DOTs to be less risk of future changes by sticking to sequential numbers versus adopting mileage-based exit numbers from the outset.

A number of early adopters of exit numbering (such as Colorado DOT and Georgia DOT) were "punished" for it by having to change to mileage-based exit numbers at a later point; in Colorado DOT's case this resulted in the operation of a dual numbering scheme ("MILE XX" numbers that were mileage-based, co-posted with "EXIT XX" numbers that were sequential).  Other state DOTs that adopted exit numbering in the late 1960's or early 1970's, at which point most of their Interstate mileage had approved alignments, had the option of choosing either sequential or mileage-based exit numbering.  The former was very much a minority choice because milepointing had come into fashion in the mid-1960's, and mileage-based exit numbering offers the synergy of having exit numbers coordinated with mileposts, which is not available with sequential numbering.

Internationally, it seems to be generally (not always) true that countries which have prominent milepointing (or kilometerpointing) tend to use distance-based junction numbering, while ones that de-emphasize distance indications tend to use sequential junction numbering.  In Spain, for example, kilometerposts are prominent (one kilometerpost every kilometer showing route designation and kilometer, with the exception of fifth kilometerposts which are more elaborate and show route designation, kilometer, and crest of the maintaining authority), and junction numbering is usually kilometer-based.  In contradistinction, before the very recent introduction of special driver location signs (similar in function to American enhanced location reference signs), in Britain kilometerposting was generally done through little numbers attached to flexible delineator posts, sort of like station markers on California state highways but even more inconspicuous.  Junction numbering has been sequential from the start.

Interestinly, Vermont's interstates have very prominent mileposts.  The only road there with mile-based numbers is non-interstate VT 289.

[Duke87]

Re: why sequential?

Honestly I don't think anyone back in the day really put any thought into it. Counting things sequentially is by far the most obvious way to number them, so that is simply what was done without question until someone actually did the thinking and thought of a better way.

[KEVIN_224]

I still want to see how they'd renumber I-95, if ever. Delavan Avenue in Greenwich would finally be Exit 1 like it should be. Would the last exit in North Stonington be 111 or something?

I-84 renumbering would be interesting. The current Exits 3 and 4 in Danbury are very close.

[J N Winkler]

Re: why sequential?

Honestly I don't think anyone back in the day really put any thought into it. Counting things sequentially is by far the most obvious way to number them, so that is simply what was done without question until someone actually did the thinking and thought of a better way.

Counting sequentially is the obvious choice only if you are dealing with just one isolated corridor instead of a network.  This was probably the case for the first few public-authority turnpikes, but by the early 1960's serious consideration was being given to other choices, not just mileage-based exit numbering but also grid-based numbering (so that each exit has an unique number) or variants of either mileage-based or sequential exit numbering in which the exit number incorporates part of the route number.

[NE2]

The Garden State Parkway was the first, at least in the U.S., to use distance-based numbering. A 1956 map shows no exit numbers (and the parkway complete except north of NJ 17), but in 1960 it was all numbered.

[Brandon]

Re: why sequential?

Honestly I don't think anyone back in the day really put any thought into it. Counting things sequentially is by far the most obvious way to number them, so that is simply what was done without question until someone actually did the thinking and thought of a better way.

Counting sequentially is the obvious choice only if you are dealing with just one isolated corridor instead of a network.  This was probably the case for the first few public-authority turnpikes, but by the early 1960's serious consideration was being given to other choices, not just mileage-based exit numbering but also grid-based numbering (so that each exit has an unique number) or variants of either mileage-based or sequential exit numbering in which the exit number incorporates part of the route number.

However, did not the Garden State Parkway include distance-based exit numbering from the start in the 1950s?  I know that Michigan introduced distance-based numbering on I-94 early on (~1960) with no sequential numbering previously.

[PHLBOS]

I-84 renumbering would be interesting. The current Exits 3 and 4 in Danbury are very close.

See Reply #73 a few pages back (below-link):

https://www.aaroads.com/forum/index.php?topic=9411.50

I'll restate the upshoot what I mentioned then; I don't see I-84's Exits 1 through 8 changing.

[connroadgeek]

All the benefits of the mileage based system are rendered moot in our little state. Most of our exits are under two miles apart and we're not going to be adding new exits to our highways unless Route 11 gets built. If they want to fix any out of sequence exit numbers that might be worth doing, but there aren't too many instances of that. The only benefit to converting is uniformity, which I know most road geeks love, but in these financially difficult times, doing something that will cost money "just because" isn't fiscally prudent. I'd prefer every last available penny go towards increasing capacity or mass transit options, not renumbering exits or new signage. People stuck in traffic on I-95 on a daily basis don't give a damn whether the exits go in order or follow mileposting.

[mapman1071]

Hutchinson River Parkway / Merritt Parkway
King Street NY 120A/CT 120A (Hidden):
This Will Be A Oddball
Will It Be Exit 1 or 0 IN CT?
I Assume with the NY Renumbering it would be Exit 18?

Why 18? The Hutch goes past MM 20.

Then would MM 0 Be at the Bronx/Queens County Line On the Bronx-Whitestone Bridge (Hutchinson River Expressway)?

[HurrMark]

Hutchinson River Parkway / Merritt Parkway
King Street NY 120A/CT 120A (Hidden):
This Will Be A Oddball
Will It Be Exit 1 or 0 IN CT?
I Assume with the NY Renumbering it would be Exit 18?

Why 18? The Hutch goes past MM 20.

Then would MM 0 Be at the Bronx/Queens County Line On the Bronx-Whitestone Bridge (Hutchinson River Expressway)?

I am not sure where MM 0 is exactly, because I don't recall signs south of Westchester, but I am pretty sure that the last mile marker on the highway is 20. Granted, Wikipedia states it is only 18.78 miles long, so I would guess you are right and that the mileage would theoretically continue on 678 (when it is no longer a parkway) down to the Bronx/Queens Line.

[KEVIN_224]

The last mile marker on the Hutchinson River Parkway is definitely 20. My travel notes all show hitting the Connecticut border 20-some seconds after that mile marker. CT mile marker 0 sits north of the King Street overpass by a couple of feet. Pictures are from April 7, 2012 and then July 2012:

[Brandon]

All the benefits of the mileage based system are rendered moot in our little state.

Right.  Distance-based exits would at least be a navigational aid in figuring how far one is from one's destination exit.  That's how we use them here in the Midwest, even with areas where exits are only a mile or two apart.

[Roadmaestro95]

All the benefits of the mileage based system are rendered moot in our little state.

Right.  Distance-based exits would at least be a navigational aid in figuring how far one is from one's destination exit.  That's how we use them here in the Midwest, even with areas where exits are only a mile or two apart.

But when it comes to the Northeast...a lot of exits are close together and all those A-B-C-D's get confusing after awhile. Knowing Connecticut, exits are not that spaced apart as say like the New York State Thruway (which needs to be milage based instead of NJ Turnpike exit numbered based...and renumbered no less).

[froggie]

But when it comes to the Northeast...a lot of exits are close together and all those A-B-C-D's get confusing after awhile.

Even milepost-based exit numbers can be tweaked, like what's done on the GSP in Union County.

[NE2]

Even milepost-based exit numbers can be tweaked, like what's done on the GSP in Union County.

The GSP is a horrible example of tweaking exit numbers, as it violates the MUTCD
http://mutcd.fhwa.dot.gov/htm/2009/part2/part2e.htm#section2E31

At a multi-exit interchange where suffix letters are used for exit numbering, an exit of the same number without a suffix letter shall not be used on the same route in the same direction. For example, if an exit is designated as EXIT 256 A, then there shall not be an exit designated as EXIT 256 on the same route in the same direction.

Interestingly, this doesn't prohibit having exits 1 and 1A if they are two separate interchanges, rather than two ramps at the same interchange.

[hbelkins]

Even milepost-based exit numbers can be tweaked, like what's done on the GSP in Union County.

The GSP is a horrible example of tweaking exit numbers, as it violates the MUTCD
http://mutcd.fhwa.dot.gov/htm/2009/part2/part2e.htm#section2E31

At a multi-exit interchange where suffix letters are used for exit numbering, an exit of the same number without a suffix letter shall not be used on the same route in the same direction. For example, if an exit is designated as EXIT 256 A, then there shall not be an exit designated as EXIT 256 on the same route in the same direction.

Interestingly, this doesn't prohibit having exits 1 and 1A if they are two separate interchanges, rather than two ramps at the same interchange.

Exit 180 and Exit 180A on I-75 in Kentucky say hello.

[PHLBOS]

Even milepost-based exit numbers can be tweaked, like what's done on the GSP in Union County.

The GSP is a horrible example of tweaking exit numbers, as it violates the MUTCD
http://mutcd.fhwa.dot.gov/htm/2009/part2/part2e.htm#section2E31

At a multi-exit interchange where suffix letters are used for exit numbering, an exit of the same number without a suffix letter shall not be used on the same route in the same direction. For example, if an exit is designated as EXIT 256 A, then there shall not be an exit designated as EXIT 256 on the same route in the same direction.

Interestingly, this doesn't prohibit having exits 1 and 1A if they are two separate interchanges, rather than two ramps at the same interchange.

Exit 180 and Exit 180A on I-75 in Kentucky say hello.

The GSP exits for both directions of the AC Expressway are 38 for GSP Eastbound and 38A for GSP Westbound.

[Brandon]

Even milepost-based exit numbers can be tweaked, like what's done on the GSP in Union County.

The GSP is a horrible example of tweaking exit numbers, as it violates the MUTCD
http://mutcd.fhwa.dot.gov/htm/2009/part2/part2e.htm#section2E31

At a multi-exit interchange where suffix letters are used for exit numbering, an exit of the same number without a suffix letter shall not be used on the same route in the same direction. For example, if an exit is designated as EXIT 256 A, then there shall not be an exit designated as EXIT 256 on the same route in the same direction.

Interestingly, this doesn't prohibit having exits 1 and 1A if they are two separate interchanges, rather than two ramps at the same interchange.

Exit 180 and Exit 180A on I-75 in Kentucky say hello.

The GSP exits for both directions of the AC Expressway are 38 for GSP Eastbound and 38A for GSP Westbound.

I think everyone's missing the restriction here.

As NE2 posted,

At a multi-exit interchange where suffix letters are used for exit numbering, an exit of the same number without a suffix letter shall not be used on the same route in the same direction. For example, if an exit is designated as EXIT 256 A, then there shall not be an exit designated as EXIT 256 on the same route in the same direction.

Emphasis mine.

It's on the road in the same direction.  Hence, a route can have Exit 1A and Exit 1B in one direction and Exit 1 in the other.  It cannot have Exit 1 followed by Exit 1A in the same direction.

[NE2]

I think Brandon's missing the fact that these examples are in the same direction. The GSP/ACE example violates the MUTCD, but the Florence Y'all example does not.

[Brandon]

I think Brandon's missing the fact that these examples are in the same direction. The GSP/ACE example violates the MUTCD, but the Florence Y'all example does not.

Yes, but the GSP was previously mentioned as an example of a road where the numbering is screwed up.

Are there any other roads, other than the GSP, out there that have distance-based exit numbers and do not follow the MUTCD as mentioned above?

[hbelkins]

I think Brandon's missing the fact that these examples are in the same direction. The GSP/ACE example violates the MUTCD, but the Florence Y'all example does not.

Southbound I-71/I-75, Exit 180A is for Mall Road and then there's Exit 180 for US 42/127. How is that not a violation? (There is no Mall Road exit northbound).

[Brandon]

Well holy shit.  I just looked at the example from HB, and I do believe it may make a photo op during the tour for the Cincy meet next Saturday.

https://maps.google.com/maps?hl=en&ll=38.994952,-84.644868&spn=0.002406,0.005284&t=m&z=18&layer=c&cbll=38.995205,-84.645992&panoid=Hz8xT8HXqUuuUCdkTBY5yg&cbp=12,176.6,,2,-7.62

KYTC really screwed this.

[hbelkins]

I had just gone to get the Google Map link.

http://goo.gl/maps/udbv8

The Mall Road exit was built after the US 42 and KY 18 exits, and I don't think there has been a sign replacement project there since then. Perhaps it will be corrected when they replace signage in that area.