Exit numbers: Distance based number or sequential?

[Henry]

If/when New York switches from sequential to distance, for example, the exit numbers along I-890 in Schenectady would need no changing.

That isn't a case of a switchover having no effect.  I-890 was numbered according to distance as part of an experiment in the 70s.  Though apart from exit 4C, you really can't tell.

And then you have the issue of the Thruway. Since it has a starting point of New York City, or somewhere close to it, when the Thruway turns onto I-90 at Albany, it continues to increase its mileage to the west, which would violate the numbering scheme for even-numbered interstates, whose miles normally increase to the east. Also, I-87 north of Albany would be another issue, seeing that its exits repeat in different places (mainly the ones that lie south of the Thruway's terminus).

[Duke87]

The problem there is that NYSTA insists that its own mainline is more important than that of the interstates that use it, and NYSDOT has similarly refused to coordinate. The Northway has its own mileposts and exit numbers which count up from the stub end at US 20 and have nothing to do with I-87. At the very least, when distance-based numbers are put in, they should use I-87 mileage (as happens in other states with situations where an interstate leaves a toll road whose numbers do not match it - I-95 New Jersey, I-70 Kansas)... but I don't see that happening because it would make too much sense. And NYSDOT isn't going to bother changing the mileposts.

No, what we are going to see when the numbers change is basically a rehash of the status quo: the Thuway will do its own thing, and I-87 and I-90 will have three different sets of mileage-based numbers.

[mightyace]

On the same vein, the Ohio Turnpike numbering is correct for the I-80/90 and I-80 only stretches as I-80 and the Ohio Turnpike start in the same place.  Of course, the I-76 portion still uses the overall turnpike mileage instead of I-76's.

And, in PA, I-276 uses the Turnpike mileage for it's stretch of the PA turnpike.  And, I assume, so will I-95 for it's brief sojourn on the Penn Pike once the exit is finished.

Though, PA did renumber the Northeast extension to integrate it with I-476 overall mileage and when the Toll PA 60 became I-376, those exit numbers were worked into I-376's system.

[Bickendan]

One thing I've found odd, though, is that some states, like Oregon, increase the mileposts from north to south, while mileage-based exits increase from south to north. So sometimes, the exit mileage will still not match up with the highway mileage.

This is a feature of Oregon's dual highway (internal) and route (external) systems. With the exception of I-5 (Hwy 1) and I-205 (can't recall the Hwy number off hand), all north-south highways have their origin at the Columbia River or northern terminus, and mileage increases going south. The only freeway this affects is OR 217, with Exit 0 at US 26 and exit 8 at I-5, and it's not that much of an issue, as it's mileage based. Also, you'll often times see mileage resets on a given route, as the Hwy number doesn't correspond with the signed Route number. For example, OR 22 has Mile 0 at US 101, at the eastern end of the OR 18/22 duplex, and at I-5 in Salem, where it becomes a freeway (with that series of exit numbers). The underlying highway under the western portion of OR 22 could have followed OR 18 past the duplex, for example (it doesn't; this happens more with routes past Bend).

[Bickendan]

Kilometer-based exits. Baring that, mileage. To those who like Sequential, I give you this clusterfuck: E15 in Spain. Aside from the straight forward hopping back and forth between A-7 and AP-7 (and to A-70) and distance exits from its western end, things fall apart near the Murcia/Valencia border, where the origin swaps (France) and sequential exits start co-mingling and usurping the distance exits.

A7(103)/E5
A7(105)
A7(106A)
A7(106B)
A7(107)
CalleBar
A7(108)
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A7(110A)
A7(110B)
A7(111)
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A7(133)/AP7(133)
AP7(142)
AP7(153)/A7(153)
A7(155)
A7(157)/AP7(157)
AP7(172)
AP7(181)/A7(181)
A7(181A)
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A7(186)/AP7(186)
AP7(200)
AP7(213)
AP7(214)/A7(214)
A7(217)
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A7(235)
A7(238A)
A7(238B)
A7(238C)
A7(240)
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A7(246B)
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A7(254)
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A7(305)
N340
CalCor
CalMonCor
CalRanRioVer
AvFen
CalPueCru
CalCap
AvSal
PlaCab
CalRam
CalExt
CalA
E902
GR5300
N323
A44
A7(LasVentillas)
A7(Carchuna)
N340
(CastillodeBanos)-- N340
(LaRabita) -- N340
A7(375)
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Andalusia/Murcia
A7(566)
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A7(662/764)
A7(664/763)
A7(667/760)
A7(672/755/83)
A7(675/752/82)
Murcia/Valencia
A7(81A) http://maps.google.com/maps?hl=en&ie=UTF8&ll=38.12264,-0.96817&spn=0.017927,0.036864&z=15
A7(81B)
A7(80)
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A7(78)
A7(77)
A7(724)
A7(722)
A7(719)
A7(714)
A7(73)
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A7(71B)
A70(71A)
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AP7(67)
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AP7(527)/A7(890)
A7(524)
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A7/AP7(480)
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Valencia/Catalonia
AP7(41)
AP7(40)
AP7(39A)
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AP7(33)
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B30(2)
B30(3)
B30(4)
AP7(21)
B20(7)
B30(8)
AP7(20)
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AP7(18)
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España/France

[english si]

Kilometer-based exits. Baring that, mileage. To those who like Sequential, I give you this clusterfuck: E15 in Spain. Aside from the straight forward hopping back and forth between A-7 and AP-7 (and to A-70) and distance exits from its western end, things fall apart near the Murcia/Valencia border, where the origin swaps (France) and sequential exits start co-mingling and usurping the distance exits.

A mass of logical fallacies in there, jumping to logical conclusions from looking at a straw man.

1)Sequential numbering isn't to blame for the idiosyncrasies of Spanish route classification - it doesn't cause the road to change numbers between AP-7 and A-7, the change in status does (I'm not sure about A-70 as I've not looked there, and the B30 exits aren't on the AP-7, though the B30 is frontage roads)
2)Sequential numbering isn't to blame for the Spanish political system - that the change from distance-based from the south to sequential from the north is at a border between two autonomous communities is telling.
3)This seems to be a mess as there are two different systems in play, and a conversion from sequential to km-based - with a change in end points (that happened slightly later than some of the exit number changes in the north) - is on-going. I find it hard to see how this is sequential exit numbers' fault!

Imagine that the US ended the horrible (if the roads are meant to be interstate, why do they not have one numbering system from end to end?) practise of resetting interstate exit numbers at state lines. Spain is federal, and autonomous communities are what they are labelled - autonomous: they are entities that are close to what states are. Take I-81, and imagine if New York, like today, was being stubborn about changing to distance-based, and Virginia was being slow about not having the mile markers start at the state line and NY and PA are being stubborn about the route changing from being north to south to being south to north. That's AP-7 in Spain.

Look at, say, I-95 from DC to Boston to see a bigger mess of exit numbering: several different start points, a mix of both systems, low numbered exits close to each other (not to mention the mess wrt the gap, and also the two I-95 segments in the Newark area). The only thing going for it is that they do all increase in the same direction.

As for me, I can see the merits in both systems, and don't mind which system is used, provided that they are used well to make it easy to navigate. The problem with the E15/AP-7 route in Spain is that the system keeps changing - end points, sequential/distance-based - in a few years, provided things stay static, it will be sorted. It's the changing that is causing the mess, not either of the systems.

[vdeane]

Imagine that the US ended the horrible (if the roads are meant to be interstate, why do they not have one numbering system from end to end?) practise of resetting interstate exit numbers at state lines.

You want four-digit exit numbers?  Last time I checked, the US is a LOT bigger than the UK (or Spain).

[hobsini2]

The current system of mileage based numbers is best because if you have a new exit built on the existing highway, it will not get placed out of order as opposed to sequenced exits.  I also think that all interstates and interstate-grade highways should use them.  Here in Illinois, the tollways don't use them although that is currently being added to the actual signs.  But highways like the Elgin-O'Hare Expy, US 20 around Rockford and IL 394 do not use the exit tabs at all.  They should have the miles based on a system similar to Wisconsin.  Both US 151 and US 41 use exit tabs now starting at the beginning of the route number and not at the physical beginning of the highway.

[agentsteel53]

2)Sequential numbering isn't to blame for the Spanish political system

the average driver doesn't care about politics and bureaucracy.  he just wants to get to point B.

number the damn things consecutively. 

[english si]

Imagine that the US ended the horrible (if the roads are meant to be interstate, why do they not have one numbering system from end to end?) practise of resetting interstate exit numbers at state lines.

You want four-digit exit numbers?  Last time I checked, the US is a LOT bigger than the UK (or Spain).

That's one of the problems with distance-based numbering, that longer numbers (3- and 4-digits) come about, compared to sequential.

And sure it's the case that the US has a lot more longer routes that would trip the 4-digit mark. However, if France and Spain had a grid system, rather than a radial system, they'd have routes that would have that problem (E5 and E15 in both countries, E50, E60 and E70 in France, E90 in Spain). E15 in Spain is along the A-7/AP-7 that we talk about above, which would mean 4-digit exit numbers near French border once Catalonia sorts itself out. And Germany's A7 is close to that mark, but they use sequential exit numbering. Sweden and Norway have a couple of 1000+km routes as well.

But, yes I'd rather 4-digit numbers than having such things as two I-95 exit 1s within 15 miles of each other because I-95 in Delaware is short. The main navigational bonus of mile-based exit numbering isn't good if you need to be in the same state before knowing how far to go before your exit - in Europe it's harder to deal with, and less pressing, as the main road numbers change at the borders (E roads in Norway and Denmark as they enter Sweden excepted) but in America it can be done.

2)Sequential numbering isn't to blame for the Spanish political system

the average driver doesn't care about politics and bureaucracy.  he just wants to get to point B.

number the damn things consecutively. 

My point was that sequential numbering isn't to blame for the mess of numbering on that road, not that the damn things shouldn't be numbered consecutively - Bickenden posted the exit numbers of a road during the middle of a change of exit numbering paradigm, where (like in America), some autonomous communities/states aren't up-to-date with changing the exit numbers.

I totally agree with your sentiment, hence why deanej had a go at me for saying that exit numbers on interstates shouldn't reset at state lines!

[agentsteel53]

actually, upon closer inspection, it's not at the Valencia/Catalonia line that things change, but a few exits before it.  WTF?

how autonomous is this autonomous region anyway?  I-40 doesn't change exit numbering scheme when going through a reservation in New Mexico. 

[english si]

No, the exits before have two numbers as they have only just changed to distance-based from the south and mapping is poor - notice that they have two (or three) numbers for those couple of junctions (perhaps signage north of the border refers to the old numbers, hence the confusion).

Autonomous communities have about the same level of autonomy as states - 18% of spending is federal, 51% of spending is by smaller entities (mostly autonomous communities and the provinces in them). The boundary we are talking about is also the boundary of the edge historic Catalunya, which doesn't aid (the Basque Country hasn't done the renumbering of autovia from Nx to A-x and autopista from Ax to AP-x yet) willingness to acquiesce to diktats from Castillian Madrid.

[thenetwork]

Mileage-based is far superior than sequential.  As much as I liked the Ohio Turnpike using sequential for almost 50 years, it was getting a bit confusing near the end when they were adding more exits.

For a while, in sequential order, there was:

Exit 7 (Now Exit 118) -- US-250
Exit 7-A (Now Exit 135) -- Baumhart Road
Exit 8-A (Now Exit 142) -- I-90/SR-2 East
Exit 8 (Now Exit 145) -- SR 57

Had the Ohio Turnpike stayed sequential, It would have been interesting to see the confusion had Exit 140/SR-58 would have been if numbered Exit 7-B. Going Exit 7, 7-A, 7-B, 8-A 8 just doesn't look or sound right. Plus SR-58 is a lot closer to the 8 & 8-A exits than the "parent" Exit 7.

I'm still ticked off that the OTC renamed Exit 10 as Exit 161 -- Exiting eastbound, mile marker 162 is just inside the first few feet of the exit lane.  It would have made more sense.

[Duke87]

Imagine that the US ended the horrible (if the roads are meant to be interstate, why do they not have one numbering system from end to end?) practise of resetting interstate exit numbers at state lines.

Look at it this way: in Europe, is it typical for motorways to keep the same system of exit numbers between multiple countries, or do they reset at the border?
Well, it's the same here. They reset at the border. The only difference is that we have a system of freeways that is consistent across state lines whereas Europe does not (E roads don't count, they aren't all freeways and are more akin to our US routes).

There are good reasons why each state has its own set of numbers. First of all, each state maintains its own portion of the highway, so there would be a lot of coordination required to measure mileage and number exits continuously across state lines which is too much to expect. Realign the highway in one spot and you throw the mileage of the whole damn thing off. Can every state down the line be expected to adjust? (Answer: no. Look at the Hutch/Merritt situation) Secondly, it's simply for brevity's sake. Many interstates would have exit numbers stretching well past 1000 if continuously numbered by mileage (I-90 would go over 3000!). It starts to get clunky to say "take exit 2347".

Besides, the reset isn't arbitrary. It happens, reliably, at the state line. We're used to this and our speech adjusts for it. If I say "exit 3 off I-95" around here, I mean the one in Connecticut. If I mean the one in Rhode Island, I will say "exit 3 off I-95 in Rhode Island" (if that isn't already clear from the context).

[relaxok]

There are good reasons why each state has its own set of numbers. First of all, each state maintains its own portion of the highway, so there would be a lot of coordination required to measure mileage and number exits continuously across state lines which is too much to expect. Realign the highway in one spot and you throw the mileage of the whole damn thing off. Can every state down the line be expected to adjust?

Wow I hadn't even thought of that -- that's actually a reason against mileage based in general.  ALL the later numbers have to change if a highway's route gets significantly altered so that the mileage after that point (going up in numbers) has changed at all.. granted, that doesn't happen that often.  But in some areas, neither does adding new exits.

I'm still conflicted about it but that's an interesting wrinkle.

[agentsteel53]

usually in the case of realignment they don't bother.  no one cares if it's exit 383 or 384 because of a shortening 200 miles back.

I wonder what they'll do with the exits on US-395 north of Reno when it re-enters California.  The exits start at 1, despite there being several hundred miles of US-395 south of there.  There is a freeway interchange at CA-203 heading to Mammoth on the south segment of the route, but it is unnumbered.  This implies the theoretical possibility of two exit 1's on US-395 if they make it a full freeway through Adelanto where it splits off I-15.

[relaxok]

A minor realignment might make not much difference, of the sort that usually happens with interstates.. but what about a re-route of a highway that takes 5-10 miles of previously separate road and makes it part of a larger highway -- say, starting it earlier on a road that previously was not part of any route.    Then to keep with the scheme you would need to move every later exit further down since the new exits would be 'negative' numbers compared to say, exit 1 that was previously the first on a route.   What about state highways where this sort of major change happens more often? 

I'm not sure how often these various things happen compared to each other, but, it's worth considering that when the mileage is no longer correct, the distance method starts to get kind of head-scratchy (or else would keep getting renumbered past the location of the change.. which could be at the beginning!)

[Hot Rod Hootenanny]

A minor realignment might make not much difference, of the sort that usually happens with interstates.. but what about a re-route of a highway that takes 5-10 miles of previously separate road and makes it part of a larger highway -- say, starting it earlier on a road that previously was not part of any route.    Then to keep with the scheme you would need to move every later exit further down since the new exits would be 'negative' numbers compared to say, exit 1 that was previously the first on a route.   What about state highways where this sort of major change happens more often?  

I'm not sure how often these various things happen compared to each other, but, it's worth considering that when the mileage is no longer correct, the distance method starts to get kind of head-scratchy (or else would keep getting renumbered past the location of the change.. which could be at the beginning!)

Ask the folks in Tennessee.
Due to the cancelation of Sam Cooper Blvd. in Memphis, I-40 was rerouted onto a beltway that added 5 miles to it's length.  

[agentsteel53]

that is a problem of both mileage-based and sequential addressing, and the solution is either to renumber everything, or to have the spur have its own set of numbers.  for example, start at exit A1, and then after A33 or whatnot we join the older section and we start at 1.  

(I don't think drivers would be very good at dealing with negative numbers counting down, so I would not recommend that.)

[Kacie Jane]

A minor realignment might make not much difference, of the sort that usually happens with interstates.. but what about a re-route of a highway that takes 5-10 miles of previously separate road and makes it part of a larger highway -- say, starting it earlier on a road that previously was not part of any route.    Then to keep with the scheme you would need to move every later exit further down since the new exits would be 'negative' numbers compared to say, exit 1 that was previously the first on a route.   What about state highways where this sort of major change happens more often? 

I'm not sure how often these various things happen compared to each other, but, it's worth considering that when the mileage is no longer correct, the distance method starts to get kind of head-scratchy (or else would keep getting renumbered past the location of the change.. which could be at the beginning!)

That sort of happened in New Jersey when the Somerset Freeway was finally officially cancelled.  I-287 was redefined to start at the Turnpike instead of where I-95 would have split off onto the unbuilt road, taking over 2-3 miles of what had been signed as I-95.  So the highway was re-mileposted, and every exit number went up by a couple (I forget exactly how much).

So it does happen, but I'd imagine it's fairly rare.

[Duke87]

Usually if there is a plan from the beginning to extend a highway southward or westward, the exits will be numbered to account for this. For unplanned extensions of this nature, you have to renumber all the exits regardless of whether they are distance based or sequential.

As for mileage corrections in the event of a realignment, you might think the ideal way to do it would be to repost all the miles (though, not necessarily renumber all the exits) down the road, but this is usually not done. If a road is shortened, the mileposts will have a skip. If it is lengthened, some numbers will be used twice with "A" and "B" suffixed after them. Besides it generally not being worth the effort, the fact of the matter is that mileposts are not about precisely measuring distance (and hey, if something is 168 miles away rather than 167, who notices?) - they are about bookkeeping. Being able to say "I'm on I-999 at mile marker 123.4" and have that identify a specific unique location (for emergency response, structure indexing, etc.) is far more important than being able to say exactly how far you are from any other mile marker on the road.


I don't like kilometer based exit numbers because it seems like they advance too fast. But that's probably just bias of what I'm used to.

[Sykotyk]

Most non-Interstate freeways (i.e., state and U.S. routes) that use milemarker exits, use them regardless where the road is a freeway, expressway, two-lane, etc. Now, the nasty little truth about mileposts is that they're not always entirely accurate themselves. For the same reason the exit numbers won't line up. If a state builds a bypass that adds 1 mile to the overall length, they may simply 'omit' a mile somewhere when there's a multiplex to make way. In fact, that is probably what can happen to US71 when it turns into I-49. Since nobody knows exactly. They may put up new mileposts, but they may leave them old ones alone for cost sake. If so, they can 'fudge' them a bit.

The greatest thing about mileage-based exits compared to sequential, that nobody seems to argue about, is that it gives you a handy rough guide of how many more miles you must travel to reach your exit by simply noting your milepost or the last exit you past. You get no advantage whatsoever to a sequential system. Small states can get away with it because you may never be too far from your exit. But, driving the NY Thruway will enlighten you to have annoying it is to never truly know how far you must travel to reach Exit 48. Even if you are counting down exits, the rare xA exit will just drive you crazy.

Sykotyk

[huskeroadgeek]

The greatest thing about mileage-based exits compared to sequential, that nobody seems to argue about, is that it gives you a handy rough guide of how many more miles you must travel to reach your exit by simply noting your milepost or the last exit you past. You get no advantage whatsoever to a sequential system. Small states can get away with it because you may never be too far from your exit. But, driving the NY Thruway will enlighten you to have annoying it is to never truly know how far you must travel to reach Exit 48. Even if you are counting down exits, the rare xA exit will just drive you crazy.

Sykotyk

This to me is the best reason for mileage-based over sequential exits. It is so much easier to know at any point how far you are from your exit and in figuring up total mileage for a trip. I remember being annoyed back in the 90s when I was making trips to or through Georgia and Florida in having to actually count up the mileage between the red arrows on the interstates rather than being able to add things up quickly just by looking at the exit numbers. Fortunately, both states now use mileage-based exit numbers.

As a general rule, I think mileage-based exit numbers are better in most states. Especially in places where there are long stretches of highway in the same state sequential exits make almost no sense. If someone is traveling say from east Texas to west Texas on I-10, it is so much more useful to know at any point during that long trip how far they are from their destination just by doing easy math between the exit numbers than it would be knowing how many exits there are between the two points. There are some places however where I think sequential numbers can work. Sequential exits make more sense in small states in size, particularly in the northeast where exits are spaced closely together and have relatively short stretches of highway within the state. Those states also happen to be the ones that still have sequential-based numbers. New York is the only state I can think of that really should have mileage-based numbers-if not for the whole state at least having them for the Thruway would be helpful.

[myosh_tino]

It would be interesting to see what California would do if I-40 is ever extended westward from Barstow to CA-99 or I-5 along what is currently CA-58.  I would guess that all exits along the current stretch of I-40 would have to get renumbered.  We're not talking a piddly 1 or 2 miles but at least 130 miles and potentially 160 miles depending on where the extension ends (CA-99 or I-5).

My take on the original topic is I prefer mileage-based exit numbering as it's easier to judge driving distances to your desired exit.

[english si]

Imagine that the US ended the horrible (if the roads are meant to be interstate, why do they not have one numbering system from end to end?) practise of resetting interstate exit numbers at state lines.

Look at it this way: in Europe, is it typical for motorways to keep the same system of exit numbers between multiple countries, or do they reset at the border?

The road number changes and exit numbers 'reset' as you are on a different road. However they don't reset when the numbers don't change. They don't reset at the borders of Spanish autonomous communities or German Lande, both of which are equivalent to states. Likewise crossing from Wales to England (Scotland-England is a bit different as the motorway changes number at the northernmost exit in England, due to a quirk of history), or Flanders to Wallonia and the exit numbers carry on as if the internal boundary wasn't there.

Well, it's the same here. They reset at the border. The only difference is that we have a system of freeways that is consistent across state lines whereas Europe does not

Which isn't true - in North America, motorways change number when they cross country boundaries, just like in Europe and just like in America, European motorways (with some exceptions) don't change number when they cross between 'states'. However, in Europe, these roads don't reset their exit numbering when they cross state lines and don't change numbers. They may reset their chainage, but not exit numbers. So there's the difference - Spain, Germany, Belgium and the UK don't reset exit numbers when roads cross 'state' boundaries, but the US does.

You make a huge category error when you equate European countries with US states - at least when it comes to roads (other issues are clouded by the EU, the Council of Europe and other international bodies).

There are good reasons why each state has its own set of numbers. First of all, each state maintains its own portion of the highway, so there would be a lot of coordination required to measure mileage and number exits continuously across state lines which is too much to expect.

As do all Spanish autonomous communities, German Lande, Belgian linguistic areas and British nations, but exit numbers are continuous in those countries.

Realign the highway in one spot and you throw the mileage of the whole damn thing off.

A problem with mileage-based exit numbers, not a problem with treating interstates as inter-state roads rather than a load of state roads with one numbering system (although getting the other states to comply is).

Secondly, it's simply for brevity's sake. Many interstates would have exit numbers stretching well past 1000 if continuously numbered by mileage (I-90 would go over 3000!). It starts to get clunky to say "take exit 2347".

A problem aggravated with mileage-based numbers. Sequential will reduce the number of 4-digit exits, though you'd still have many. And yes it gets clunky, but that's the problem of having a big country. Perhaps get rid of the first number of 4-digit exits? At least then it would be 1000 miles between exits on the same road with the same number.

My take on the original topic is I prefer mileage-based exit numbering as it's easier to judge driving distances to your desired exit.

Only if you are in the same state as your exit, or know how far it is to get to the state line of the state where your exit is and can then add the two numbers together.