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[jakeroot]

Seriously guys, what's wrong with this?

Zero advantage over sequential non-alphabetized exiting.

How so?  Its a reasonable compromise. By setting the numbers to the nearest milepost -1, it works out reasonably well. Most highways have lots of letter suffixed exits. Not sure why its a big deal as long as we are keeping them to A's and B's.

Why are we compromising at all? What are drivers gaining having exits with A's and B's, over a single-number-per-exit system? The advantage of mileage-based exits is totally lost on a very short freeway, especially when (as I pointed out above) they're not even correct!

[famartin]

Seriously guys, what's wrong with this?

Zero advantage over sequential non-alphabetized exiting.

How so?  Its a reasonable compromise. By setting the numbers to the nearest milepost -1, it works out reasonably well. Most highways have lots of letter suffixed exits. Not sure why its a big deal as long as we are keeping them to A's and B's.

Why are we compromising at all? What are drivers gaining having exits with A's and B's, over a single-number-per-exit system? The advantage of mileage-based exits is totally lost on a very short freeway, especially when (as I pointed out above) they're not even correct!

But they are close to correct. Remember, the point of mileage-based exits is to get an approximate distance to the next exit.  Not pure accuracy, just approximate. And the numbers I came up with do that. Subtracting one mile and putting the exits within a half mile of the said milepost on that number, you get an approximate mileage based numbering which is not too filled with letters but still does the intended purpose of giving an approximate distance between exits. Its not perfect but it does the job without the alphabet soup.

I-395 in VA isn't really sequential, and its not quite mileage based either. Best estimate of the actual distance in VA based on the mileposts is around 10 miles from what VA considers to be Mile 0 to the DC line, so exits 2-10 make sense, even if fudged a bit.

Now, if you are really only looking to limit confusion for drivers... I-395 in DC shouldn't even have its own numbering scheme. MD and VA combined the beltway into one scheme. Why shouldn't DC and VA do likewise, and just continue the VA numbering to 295 in DC?

[1995hoo]

On the other hand, with a road as short as I-395/I-695 in DC, is there really much need for being able to get an approximate distance to the next exit? I certainly recognize the benefit of that on long drives, and I also recognize the benefit of not having to renumber the exits if you add a new one (compare to the Thruway's Exit 21 > 21B > 21A > 22 sequence, for example). But neither of those seems to be the case here. True, a trip across that stretch could be part of a longer drive for someone passing through the area, but it's still an insignificant distance.

(For comparison, if I get on I-95 to drive south to Florida, the exit numbers tell me it would be 173 miles to North Carolina if I stayed on I-95 to Richmond, and that helps me gauge my progress even if it doesn't really tell me anything about the overall distance remaining for the trip. But mileage-based numbers a two-mile segment of I-395 in the District wouldn't serve a similar purpose because it's simply too small a distance to matter in the overall context.)

[jakeroot]

Seriously guys, what's wrong with this?

Zero advantage over sequential non-alphabetized exiting.

How so?  Its a reasonable compromise. By setting the numbers to the nearest milepost -1, it works out reasonably well. Most highways have lots of letter suffixed exits. Not sure why its a big deal as long as we are keeping them to A's and B's.

Why are we compromising at all? What are drivers gaining having exits with A's and B's, over a single-number-per-exit system? The advantage of mileage-based exits is totally lost on a very short freeway, especially when (as I pointed out above) they're not even correct!

But they are close to correct. Remember, the point of mileage-based exits is to get an approximate distance to the next exit.  Not pure accuracy, just approximate. And the numbers I came up with do that. Subtracting one mile and putting the exits within a half mile of the said milepost on that number, you get an approximate mileage based numbering which is not too filled with letters but still does the intended purpose of giving an approximate distance between exits. Its not perfect but it does the job without the alphabet soup.

But you're not explaining why "approximate distance to the next exit" is an important parameter in the context of this whole freeway. To introduce mileage-based exit numbering, you have to fudge the numbers so as to not create an insane alphabet soup, but then you're still left with an almost-entirely suffixed exit system (aka, regular alphabet soup). And for what?

Being in the correct lane and locating the correct exit is a far more important goal for this freeway, and I see that being more easily achieved with quickly-identifiable exit numbers, and the best way to achieve that is to use sequential numbering where a single number is tied to a single exit.

Now, if you are really only looking to limit confusion for drivers... I-395 in DC shouldn't even have its own numbering scheme. MD and VA combined the beltway into one scheme. Why shouldn't DC and VA do likewise, and just continue the VA numbering to 295 in DC?

But that would only make it more confusing for drivers. You'd then be looking at at least three characters for the vast majority of exits along that stretch. And you'd still have to wrangle with the basic fact that most drivers on this freeway are not driving long distances and gain nothing with mileage-based exit numbers.

[famartin]

Seriously guys, what's wrong with this?

Zero advantage over sequential non-alphabetized exiting.

How so?  Its a reasonable compromise. By setting the numbers to the nearest milepost -1, it works out reasonably well. Most highways have lots of letter suffixed exits. Not sure why its a big deal as long as we are keeping them to A's and B's.

Why are we compromising at all? What are drivers gaining having exits with A's and B's, over a single-number-per-exit system? The advantage of mileage-based exits is totally lost on a very short freeway, especially when (as I pointed out above) they're not even correct!

But they are close to correct. Remember, the point of mileage-based exits is to get an approximate distance to the next exit.  Not pure accuracy, just approximate. And the numbers I came up with do that. Subtracting one mile and putting the exits within a half mile of the said milepost on that number, you get an approximate mileage based numbering which is not too filled with letters but still does the intended purpose of giving an approximate distance between exits. Its not perfect but it does the job without the alphabet soup.

But you're not explaining why "approximate distance to the next exit" is an important parameter in the context of this whole freeway. To introduce mileage-based exit numbering, you have to fudge the numbers so as to not create an insane alphabet soup, but then you're still left with an almost-entirely suffixed exit system (aka, regular alphabet soup). And for what?

Being in the correct lane and locating the correct exit is a far more important goal for this freeway, and I see that being more easily achieved with quickly-identifiable exit numbers, and the best way to achieve that is to use sequential numbering where a single number is tied to a single exit.

Now, if you are really only looking to limit confusion for drivers... I-395 in DC shouldn't even have its own numbering scheme. MD and VA combined the beltway into one scheme. Why shouldn't DC and VA do likewise, and just continue the VA numbering to 295 in DC?

But that would only make it more confusing for drivers. You'd then be looking at at least three characters for the vast majority of exits along that stretch. And you'd still have to wrangle with the basic fact that most drivers on this freeway are not driving long distances and gain nothing with mileage-based exit numbers.

Wait, what?  OK, at this point I just think you are going to argue til everyone believes you are right or just gives up. So I'll give up now.

[1995hoo]

It seems to me most drivers are accustomed to having exit numbers reset at state lines. I don't see why I-395 should be any different.

I always found the argument that the Beltway exit numbers were "confusing" when they reset at the state line to be a bit absurd and I think if anything the current system where the numbers run from 2 to 57 and then three miles later jump to 173 is likely to be a lot more "confusing" to the average driver (regardless of the principle that I-95's numbers trump I-495's). The one thing that maybe had some validity on the Beltway was that some exit numbers were duplicated in Virginia and Maryland and that because it's a loop route, that meant the duplication was more proximate than will normally be the case on longer-distance thru Interstates. But even then, people don't seem to be confused by the two Exit 1s located 11.5 miles apart on I-81 in Maryland and Pennsylvania.

[jakeroot]

Wait, what?  OK, at this point I just think you are going to argue til everyone believes you are right or just gives up. So I'll give up now.

I'm just trying to present an alternative to the holier-than-thou "mileage based exit numbers" that are primarily advantageous over longer distances. This freeway is only like 3.5 miles long.

[vdeane]

The advantages of mileage-based numbers are why they are the nation-wide standard (aside from Nova Scotia and Newfoundland, they're pretty much the standard of the entire continent, aside from Mexico, which doesn't pervasively use exit numbers).  Why should DC be different than the (hopefully eventually) entire rest of the country?  The sequential numbering scheme proposed would have a larger disparity between the exit number and mileage than any of the examples of sequential numbers remaining in mileage-based states.

As for the proposals being off anyways... my proposal isn't off by much (and by how much depends on what rounding method is used... I think it's interesting that the standard is the one that maximizes alphabet soup, that seems a little short-sighted to me, but it is what it is).  The 0s are from 0-0.8; the 1s are from 0.8-1.6; the 2s are from 1.6-2.5; the 3s are from 2.5-3.4; and the 4s are at ~3.7 (for I-195, my proposed 1 is at 0.9 and my proposed 2 is at 1.1).  Actually, looking at these, they aren't even off; I'm just choosing my rounding method on the fly for whatever is most convenient.

[1]

The 0s are from 0-0.8; the 1s are from 0.8-1.6; the 2s are from 1.6-2.5; the 3s are from 2.5-3.4; and the 4s are at ~3.7 (for I-195, my proposed 1 is at 0.9 and my proposed 2 is at 1.1).  Actually, looking at these, they aren't even off; I'm just choosing my rounding method on the fly for whatever is most convenient.

That system is equivalent to using 0.85 miles = 1 exit number and rounding up. That means they're not actually mile markers.

[jakeroot]

The advantages of mileage-based numbers are why they are the nation-wide standard...

...Because they normally line up with the route mileage. Yours, at best, barely meet that goal. To someone driving, it's far enough off that I fail to see how it could be useful. And there's still zero consideration for potential confusion around numerous "A" and "B" suffixes plastered across every sign. Has there ever been a consideration for how drivers could be confused by having six separate exits with an "A" attached to them? Suffixed exits are fine when not avoidable, but they're not typically ideal. Here, they're entirely avoidable yet we insist on it for unknown reasons beyond "it's just what you do".

[famartin]

The advantages of mileage-based numbers are why they are the nation-wide standard...

...Because they normally line up with the route mileage. Yours, at best, barely meet that goal. To someone driving, it's far enough off that I fail to see how it could be useful. And there's still zero consideration for potential confusion around numerous "A" and "B" suffixes plastered across every sign. Has there ever been a consideration for how drivers could be confused by having six separate exits with an "A" attached to them? Suffixed exits are fine when not avoidable, but they're not typically ideal. Here, they're entirely avoidable yet we insist on it for unknown reasons beyond "it's just what you do".

Alright, I'll leap back in...

Lets be truly honest here... the only way most exit numbers are actually useful, on a highway with a lot of them, is by giving you an idea of how far to the next exit. On a road with very few exits, like, say the NJ Turnpike, they are so few and far apart that the numbers are useful even though they are sequential. However, on your average interstate where exits are fairly frequent, the exit numbers don't stick in my mind for any reason other than to give me an idea of how far to the my intended exit.  If you listen to WTOP, I hear them mention the intersecting roads a lot more than the actual exit numbers. They do mention them sometimes, but the emphasis is definitely on the intersecting road, not the exit number.  Thus, for a road like I-395, they aren't even that important. I'm much more likely to advise someone to take the 12th Street exit than Exit 3 or whatever it is.

Since they aren't that important, might as well conform to standard.

[1995hoo]

I found Virginia’s exit numbers on the Beltway a lot easier to remember when they were sequential, but certainly that could be from familiarity after growing up seeing those numbers.

Exit numbers are useful in giving directions, though. They’re an extra piece of information and one that’s easy to look for once known.

[Mapmikey]

Does it make any difference that there don't appear to be any sort of mile markers posted on I-395 in DC?

I-66 in DC has neither mile markers nor exit numbers (though does still have this nifty District of Columbia shield - https://goo.gl/maps/uPuyoWQQuo4drqgg9)

The problem in general is that having a single standard for a system with 47,000+ miles in widely varying settings is that the single standard doesn't make the best sense in all cases. 

I-95 in Virginia once had 3 Exit 2s, 3 Exit 3s and 3 Exit 4s at one point because of the Richmond-Petersburg Tpk and the DC Beltway having separate numbering systems in addition to 95's.  So the national standard makes a ton of sense to fix that.

Given that DC changed it to mileage based, then changed it back suggests people were having issues with it.  I think most people would have an easier time remembering integers than a series of suffixes A-D on multiple sets of exits.

[1995hoo]

....

Given that DC changed it to mileage based, then changed it back suggests people were having issues with it.  I think most people would have an easier time remembering integers than a series of suffixes A-D on multiple sets of exits.

In that vein, I think the point I previously made is of some significance:

Another factor—and it's one that I recognize may not be on vdeane's radar for obvious reasons—is the history of problems the DC EMS department has had in dispatching emergency response personnel. There have been all sorts of problems over the years involving teams dispatched to the wrong locations, and that highway has been a problem spot multiple times. Anything they can do to reduce ambiguity or possible reasons for confusion is probably a good thing, especially given how many accidents that road sees, and I'd suggest that sequential exit numbers without letter suffixes would be more specific for emergency response purposes because under that system each exit will have a fully unique number, rather than a partially unique one differentiated by suffix.

[vdeane]

The 0s are from 0-0.8; the 1s are from 0.8-1.6; the 2s are from 1.6-2.5; the 3s are from 2.5-3.4; and the 4s are at ~3.7 (for I-195, my proposed 1 is at 0.9 and my proposed 2 is at 1.1).  Actually, looking at these, they aren't even off; I'm just choosing my rounding method on the fly for whatever is most convenient.

That system is equivalent to using 0.85 miles = 1 exit number and rounding up. That means they're not actually mile markers.

It's actually using normal rounding - the same rounding used for taxes and all of math - for all but one or two exits (which use the round down method that tends to be favored for exit numbers (for reasons unknown) in order to reduce alphabet soup for the 1s).

The advantages of mileage-based numbers are why they are the nation-wide standard...

...Because they normally line up with the route mileage. Yours, at best, barely meet that goal. To someone driving, it's far enough off that I fail to see how it could be useful. And there's still zero consideration for potential confusion around numerous "A" and "B" suffixes plastered across every sign. Has there ever been a consideration for how drivers could be confused by having six separate exits with an "A" attached to them? Suffixed exits are fine when not avoidable, but they're not typically ideal. Here, they're entirely avoidable yet we insist on it for unknown reasons beyond "it's just what you do".

See above.  One could also argue that many of the groupings are actually interchanges with multiple ramps - in fact, I could see a case for all of them except the 0s, especially for the 1s and 2s (not mentioning the 4s because everyone would call that ramp split one interchange).  Should this stretch of the Southern State Parkway be considered confusing alphabet soup and each ramp given a separate sequential number (it even has 28AN and 28AS!)?

[jakeroot]

The advantages of mileage-based numbers are why they are the nation-wide standard...

...Because they normally line up with the route mileage. Yours, at best, barely meet that goal. To someone driving, it's far enough off that I fail to see how it could be useful. And there's still zero consideration for potential confusion around numerous "A" and "B" suffixes plastered across every sign. Has there ever been a consideration for how drivers could be confused by having six separate exits with an "A" attached to them? Suffixed exits are fine when not avoidable, but they're not typically ideal. Here, they're entirely avoidable yet we insist on it for unknown reasons beyond "it's just what you do".

See above.  One could also argue that many of the groupings are actually interchanges with multiple ramps - in fact, I could see a case for all of them except the 0s, especially for the 1s and 2s (not mentioning the 4s because everyone would call that ramp split one interchange).  Should this stretch of the Southern State Parkway be considered confusing alphabet soup and each ramp given a separate sequential number (it even has 28AN and 28AS!)?

If we're going to use suffixed exits, then I actually don't mind using somewhat unique suffixes.

In fact, if you absolutely insist on mileage-based exits, why not do something like this?...0A, 0B, 1C, 1D, 2E, 2F, 3G, 3H, etc.

It's actually using normal rounding - the same rounding used for taxes and all of math - for all but one or two exits (which use the round down method that tends to be favored for exit numbers (for reasons unknown) in order to reduce alphabet soup for the 1s).

I think we understand that you have to round, and that rounding is sometimes necessary. But it's acceptable because you wouldn't dump mileage-based exits along a very length freeway just because of some alphabet soup in a particular neighborhood. No, you accept that it's a necessary evil. But on a freeway with almost entirely suffixed exits that's barely a few miles long, there's simply no advantage.

This is clearly a unique case, but that's just it. Insisting on applying the national standard because it's the national standard misses the point of standards, which really is to make driving easier. Multiple suffixed exits in a row just isn't easier for drivers than sequential numbering in this one instance because there are too many other things going on.

[jakeroot]

The advantages of mileage-based numbers are why they are the nation-wide standard...

...Because they normally line up with the route mileage. Yours, at best, barely meet that goal. To someone driving, it's far enough off that I fail to see how it could be useful. And there's still zero consideration for potential confusion around numerous "A" and "B" suffixes plastered across every sign. Has there ever been a consideration for how drivers could be confused by having six separate exits with an "A" attached to them? Suffixed exits are fine when not avoidable, but they're not typically ideal. Here, they're entirely avoidable yet we insist on it for unknown reasons beyond "it's just what you do".

Alright, I'll leap back in...

Lets be truly honest here... the only way most exit numbers are actually useful, on a highway with a lot of them, is by giving you an idea of how far to the next exit. On a road with very few exits, like, say the NJ Turnpike, they are so few and far apart that the numbers are useful even though they are sequential. However, on your average interstate where exits are fairly frequent, the exit numbers don't stick in my mind for any reason other than to give me an idea of how far to the my intended exit.  If you listen to WTOP, I hear them mention the intersecting roads a lot more than the actual exit numbers. They do mention them sometimes, but the emphasis is definitely on the intersecting road, not the exit number.  Thus, for a road like I-395, they aren't even that important. I'm much more likely to advise someone to take the 12th Street exit than Exit 3 or whatever it is.

Since they aren't that important, might as well conform to standard.

Look, I totally get the point of mileage-based exit numbering. I hope you don't think that I don't like it. I use it the same way as you: counting down my exits. But no one is counting down the miles to their exit on this very, very short freeway; no one gives a damn about route mileage on this very, very short freeway.

Have you considered that, if the exit numbers were easier to understand (aka, not a sea of suffixes), they might actually be helpful? And I would agree with 1995hoo above that they are actually quite useful when telling someone else when to exit, over something else like a highway number or street name.

[TheStranger]

Here's a conceptual idea I had:

Given that the new 395 as a whole (from Springfield to DC 295) is not a super long road, why not just have one exit number set that continues across the river from Virginia?

That way no need to round to -1, no need to worry about exit number duplication from the VA stretch of 395, and if mile-based, there is a logical measurement occurring (distance from I-95/I-495).

[jakeroot]

Here's a conceptual idea I had:

Given that the new 395 as a whole (from Springfield to DC 295) is not a super long road, why not just have one exit number set that continues across the river from Virginia?

That way no need to round to -1, no need to worry about exit number duplication from the VA stretch of 395, and if mile-based, there is a logical measurement occurring (distance from I-95/I-495).

This was proposed up-thread by famartin (reply #1126). I don't think this is a bad idea, but you'd still be left with all the suffixes, which is the main issue here (not mileage-based exits themselves, but rather what they can produce).

You could keep the mileage from VA I-395 going, and use unique suffixes like I proposed a couple posts up: after you cross the Potomac, you have 11A, then 11B, then 12C, then 12D, etc.

[1995hoo]

I think Dave Dildine may be a member or a lurker on this forum!

Alternative 3 is a version of mile-based that starts the sequence at 1. It also incorporates the ramps to C St SW and D St SW and assumes I-195 exiting will begin at D St NW. pic.twitter.com/nRNgAfn774

— Dave Dildine (@DildineWTOP) January 30, 2021

[vdeane]

Not sure if he's here, but he definitely is on the DCRoads.com Facebook group (where this has also become quite the discussion; I actually posted my proposed scheme there first).

If we're going to use suffixed exits, then I actually don't mind using somewhat unique suffixes.

In fact, if you absolutely insist on mileage-based exits, why not do something like this?...0A, 0B, 1C, 1D, 2E, 2F, 3G, 3H, etc.

That's a cool idea.  Not quite to the letter of the MUTCD... but certainly more in the spirit of it than straight sequential!

I think we understand that you have to round, and that rounding is sometimes necessary. But it's acceptable because you wouldn't dump mileage-based exits along a very length freeway just because of some alphabet soup in a particular neighborhood. No, you accept that it's a necessary evil. But on a freeway with almost entirely suffixed exits that's barely a few miles long, there's simply no advantage.

This is clearly a unique case, but that's just it. Insisting on applying the national standard because it's the national standard misses the point of standards, which really is to make driving easier. Multiple suffixed exits in a row just isn't easier for drivers than sequential numbering in this one instance because there are too many other things going on.

I'll admit that this is where my perfectionism and obsession with order come into play.  I'm the type of person who will rearrange cart returns at the store because I can't stand how people put the cars in willy-nilly.

[1995hoo]

I think Dave Dildine may be a member or a lurker on this forum!

....

I didn't get to post as fully as I meant to last night because the pizza man rang the doorbell right as I was hitting "Post." I'd like to post the fuller set of Dave Dildine's comments just for completion and to illustrate why I made the comment I did, vdeane's point about the Facebook group notwithstanding (I don't use Facebook and so have not seen that).

Sorry if there is some level of duplication here. Linking tweets can be problematic. If I use the button to copy the link to the tweet, invariably some gibberish characters show up after it. If I instead copy the URL in the browser's address bar, the earlier tweet of his to which he was replying shows up.

With the plan to reroute I-395 from the 3rd Street Tunnel across the entire Freeway later this year, here is a proposal for new exit numbers to replace the confusing 1A-1B-1C-1D scheme currently on the eastern half. Thoughts? @DDOTDC https://t.co/TK6htj9HPe pic.twitter.com/f3OevyLfC0

— Dave Dildine (@DildineWTOP) January 27, 2021

Let's call this "Alternative 2" for exit numbering on I-395 extended. It's more in line with FHWA's transition to mile-based numbering. For a short freeway with closely-packed exits, is this better or more confusing? @DDOTDC pic.twitter.com/ODwmhYQA8N

— Dave Dildine (@DildineWTOP) January 29, 2021

Invalid Tweet ID

Alternative 3 is a version of mile-based that starts the sequence at 1. It also incorporates the ramps to C St SW and D St SW and assumes I-195 exiting will begin at D St NW. pic.twitter.com/nRNgAfn774

— Dave Dildine (@DildineWTOP) January 30, 2021

I'll admit that this is where my perfectionism and obsession with order come into play.  I'm the type of person who will rearrange cart returns at the store because I can't stand how people put the cars in willy-nilly.

Heh, funny that I'm seeing this now. I went to Wegmans last night to avoid the expected crowds today and the carts were a jumble when I returned mine, but it was too damn windy to rearrange anything and I didn't have a pair of warm gloves with me, and I said to myself, "Damn, too bad vdeane doesn't shop at this Wegmans."

[jakeroot]

If we're going to use suffixed exits, then I actually don't mind using somewhat unique suffixes.

In fact, if you absolutely insist on mileage-based exits, why not do something like this?...0A, 0B, 1C, 1D, 2E, 2F, 3G, 3H, etc.

That's a cool idea.  Not quite to the letter of the MUTCD... but certainly more in the spirit of it than straight sequential!

Glad you like it! I'm not used to seeing suffixed exits on a regular basis, so I guess maybe I find them more confusing than most? Most non-Interstate Seattle freeways don't even have exit numbers, let alone exits with suffixes. Anything to me that reduces the level of repetition (basically, A and B over and over and over and over again) would be really great here. I think the sheer number exits (whether they're grouped or not) does lend itself to a slightly-different approach than what might normally be considered. I guess we could use mileage-based exits (I still think them being slightly off from actual mileage does, at least a bit, defeat the purpose), but I think doing nothing else to improve exit number recognition won't much improve the current situation of drivers being confused by the exit numbers.

I'll admit that this is where my perfectionism and obsession with order come into play.  I'm the type of person who will rearrange cart returns at the store because I can't stand how people put the cars in willy-nilly.

Interesting that you'd bring that up. I would think sequential numbering would come across as more orderly than repetitive suffixes. What you've proposed is ordered relative to FHWA standards, but to drivers, it may actually appear quite jumbled ("why does every exit have an A or B?").

[18 wheel warrior]

.... Heck, even 395's Virginia exits aren't completely mileage-based, although that might be irrelevant.

In Virginia all 3 digit interstate exits are all sequential.

[74/171FAN]

.... Heck, even 395's Virginia exits aren't completely mileage-based, although that might be irrelevant.

In Virginia all 3 digit interstate exits are all sequential.

I-295 and I-495 are mileage-based (though I-495's numbers continue from MD).