# Missing Exit? **URL:** \ **Category:** Factual Questions\ **Created:** [February 6, 2003, 4:02pm UTC](https://boards.straightdope.com/t/missing-exit/153215 "2003-02-06T16:02:39Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![arrbeejay](https://avatars.discourse-cdn.com/v4/letter/a/94ad74/32.png) [@arrbeejay](https://boards.straightdope.com/u/arrbeejay)\ **Post date:** [February 6, 2003, 4:02pm UTC](https://boards.straightdope.com/t/missing-exit/153215/1 "2003-02-06T16:02:39Z")
I don’t know about “the teeming millions” 😉 but I’m curious about this, so maybe others are too: I live in Westchester, New York, and commute to work in northern New Jersey. I drive home on I-87 Southbound; the last exit in Rockland County, before the Tappan Zee bridge, is “Exit 11.” The next exit, clear across the bridge in Westchester County, is … “Exit 9”! What gives?! Where is “Exit 10”? Did someone lose track? Also, the Tappan Zee bridge is described as a “floating bridge.” It always seems pretty securely attached when I’m driving across, so where does the “floating” part come into play? ---
**Author:** ![Slartibartfastt](https://avatars.discourse-cdn.com/v4/letter/s/5e9695/32.png) [@Slartibartfastt](https://boards.straightdope.com/u/Slartibartfastt)\ **Post date:** [February 6, 2003, 4:05pm UTC](https://boards.straightdope.com/t/missing-exit/153215/2 "2003-02-06T16:05:01Z")
The exit numbers are roughly equal to the mile marker of the highway they are on, they are not in numerical order unless there is an exit every mile. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [February 6, 2003, 4:21pm UTC](https://boards.straightdope.com/t/missing-exit/153215/3 "2003-02-06T16:21:37Z")
Where is it described as “Floating”? There are real floating bridges across Lake Washington, just east of Seattle. The bridges are hollow concrete (?) sections attached at either end. They actually lost one of them in a bad storm many years ago, it floated away and sections sank or were damaged. But those have nothing to do with the Tappen Zee bridge. ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [February 6, 2003, 4:26pm UTC](https://boards.straightdope.com/t/missing-exit/153215/4 "2003-02-06T16:26:51Z")
> [@](#): > > \*Originally posted by Slartibartfastt \* > \*\*The exit numbers are roughly equal to the mile marker of the highway they are on, they are not in numerical order unless there is an exit every mile. \*\* Until somewhat recently that was not the case in Georgia and Florida. It was confusing because if you were at Exit 15 and wanted to get off at Exit 19 you had no idea how long it would take to get there. ---
**Author:** ![Exgineer](https://avatars.discourse-cdn.com/v4/letter/e/a88e4f/32.png) [@Exgineer](https://boards.straightdope.com/u/Exgineer)\ **Post date:** [February 6, 2003, 4:29pm UTC](https://boards.straightdope.com/t/missing-exit/153215/5 "2003-02-06T16:29:04Z")
> [@](#): > > \*Originally posted by Slartibartfastt \* > \*\*The exit numbers are roughly equal to the mile marker of the highway they are on, they are not in numerical order unless there is an exit every mile. \*\* Not in New York. Exit numbers in interstates, including the Thruway, are consecutive. Having said that, I have no idea what happened to Exit 10, unless it was a planned exit that never got built. ---
**Author:** ![Cabbage](https://avatars.discourse-cdn.com/v4/letter/c/f07891/32.png) [@Cabbage](https://boards.straightdope.com/u/Cabbage)\ **Post date:** [February 6, 2003, 4:36pm UTC](https://boards.straightdope.com/t/missing-exit/153215/6 "2003-02-06T16:36:38Z")
**Slartibartfastt** , that would have been my guess, too, but not all interstates have their exits corresponding with mile markers; I checked a (couple of years old) map, and, sure enough, I-87 in that area is apparently one of those interstates still with numerically ordered exits. Having said that, I _am_, in fact, seeing an exit 10 on the map. I’m not at all familiar with the area, but maybe the following will mean something to \*\* arrbeejay\*\*. It looks as though while exit 11 leads west to West Nyack (I don’t see a highway number for this route, though), 10 exits directly onto highway 9W, running north-south. A possible guess: Maybe exit 10 is only accessible from I-87 northbound? And by the way, welcome to the boards, **arrbeejay**! ---
**Author:** ![NYR407](https://avatars.discourse-cdn.com/v4/letter/n/bbe5ce/32.png) [@NYR407](https://boards.straightdope.com/u/NYR407)\ **Post date:** [February 6, 2003, 4:48pm UTC](https://boards.straightdope.com/t/missing-exit/153215/7 "2003-02-06T16:48:34Z")
> [@](#): > > \*Originally posted by Slartibartfastt \* > \*\*The exit numbers are roughly equal to the mile marker of the highway they are on, they are not in numerical order unless there is an exit every mile. \*\* Not true for the road arrbeejay is talking about. The NY State Thruway has exit 20 at mile marker 100. Arrbeejay, I know the road you are talking about and the only guesses I can make are: 1. There is an exit on the south bound side with exit 10 but not the northbound side 2. The original plans had designs for an exit 10 but they changed their minds or decide to leave the number available in case the need for another exit between the two. 3. Exit 10 is a service exit for toll booth workers etc so they do not show a sign with the exit number. 4. The messed up (not likely but you never know) I have no info on the floating bridge question. Welcome aboard! ---
**Author:** ![NYR407](https://avatars.discourse-cdn.com/v4/letter/n/bbe5ce/32.png) [@NYR407](https://boards.straightdope.com/u/NYR407)\ **Post date:** [February 6, 2003, 5:08pm UTC](https://boards.straightdope.com/t/missing-exit/153215/8 "2003-02-06T17:08:11Z")
Well there definately is an exit 10, Nyak - South Nyak (click on the link and it gives you a list of the exits on the thruway in the scoll down menu) [http://www.thruway.state.ny.us/tolls/calc/index.html](http://www.thruway.state.ny.us/tolls/calc/index.html) It may be in only one direction. Check again and let us know There is no reference to the Tappan Zee being a “floating” bridge in the fact book section [http://www.thruway.state.ny.us/factbook/tz/index.html](http://www.thruway.state.ny.us/factbook/tz/index.html) ---
**Author:** ![arrbeejay](https://avatars.discourse-cdn.com/v4/letter/a/94ad74/32.png) [@arrbeejay](https://boards.straightdope.com/u/arrbeejay)\ **Post date:** [February 6, 2003, 5:08pm UTC](https://boards.straightdope.com/t/missing-exit/153215/9 "2003-02-06T17:08:25Z")
Thanks for all the replies. Wow, this thing works fast! I imagine they either planned an exit 10, then decided against it; or it’s a non-public exit of some sort (though I prefer to think they just screwed up!) I saw mention of the Tappan Zee bridge being a “floating bridge” in some “Did you know” flyer at a local eatery. I _think_ it has to do with a section of the bridge sitting on cement pilings that aren’t actually sunk into the ground. Actually, there’s another interesting fact about the Tappan Zee – it follows a lazy S-shape as it crosses the Hudson. Presumably it has something to do with being better able to withstand currents in the river. Anyway, thanks again! ---
**Author:** ![Slartibartfastt](https://avatars.discourse-cdn.com/v4/letter/s/5e9695/32.png) [@Slartibartfastt](https://boards.straightdope.com/u/Slartibartfastt)\ **Post date:** [February 6, 2003, 5:23pm UTC](https://boards.straightdope.com/t/missing-exit/153215/10 "2003-02-06T17:23:49Z")
Well I am stuck in the middle of nowhere here in Kansas and on all interstate highways that I know of the exit numbers are the same as the current mile marker. Even where there are numerous exits in cities the exits are marked as 10a,10b,10c, etc if there is more than one in a mile. As an additional observation I have noticed that on the Kansas Turnpike even the bridges are numbered by the mile marker they are on, down to thousandths of miles. ---
**Author:** ![brad\_d](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@brad\_d](https://boards.straightdope.com/u/brad_d)\ **Post date:** [February 6, 2003, 6:56pm UTC](https://boards.straightdope.com/t/missing-exit/153215/11 "2003-02-06T18:56:16Z")
Some states number their exits by mile marker (Texas and West Virginia, for example), and others number them consecutively (Pennsylvania). We’ve had a couple of threads about this, and I believe it’s pretty much a matter of state preference. There are pros and cons to each method, I suppose. A method which has almost no pros is the one California uses - not to bother numbering them at all. They just recently decided to change this, and numbers will be phased in over the next several years. [This article](http://www.dot.ca.gov/hq/traffops/signtech/calnexus/) says that they’re using the mile-based system. Maybe they’ll someday add mile markers, too - another mystifying absence in this state. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [February 6, 2003, 7:16pm UTC](https://boards.straightdope.com/t/missing-exit/153215/12 "2003-02-06T19:16:21Z")
It isn’t even consistent within a state… If you drive east from Fresno, California (which I do as often as I can!) the roads are named for their distance from the center of town, i.e., Road 42 is 4.2 miles out. But that’s the only place I’ve ever seen that does it that way! Trinopus ---
**Author:** ![toadspittle](https://avatars.discourse-cdn.com/v4/letter/t/c0e974/32.png) [@toadspittle](https://boards.straightdope.com/u/toadspittle)\ **Post date:** [February 6, 2003, 8:01pm UTC](https://boards.straightdope.com/t/missing-exit/153215/13 "2003-02-06T20:01:33Z")
Re: Part 2 of the OP: Floating Caissons: > **[Construction Engineering and Management](https://engineering.purdue.edu/CEM)** > > Known as the 'Cradle of Astronauts,' Purdue University's College of Engineering has produced 25 astronauts, including Neil Armstrong. The college also is home to such pioneers as Amelia Earhart and seven National Medal of Technology and Innovation... > [@](#): > > One of the methods that allows a fast paced construction of docks is based on the use of floating caissons. The floating caissons are prefabricated concrete box-like elements with cylinder cavities or cells Tappan Zee in particular: [http://www.nycroads.com/crossings/tappan-zee/](http://www.nycroads.com/crossings/tappan-zee/) > [@](#): > > BUILDING THE FOUNDATIONS: Eight underwater concrete caissons, which support about 70 percent of the bridge’s dead weight, are themselves supported by steel piles driven to rock. \*\*The caissons incorporate a “buoyant” design that stores pressurized air within small compartments. \*\*Water is periodically pumped out of these compartments, which range in number from 8 to 24 in each caisson, to achieve the desired buoyancy. This innovative design saved millions of dollars in construction costs. ---
**Author:** ![arrbeejay](https://avatars.discourse-cdn.com/v4/letter/a/94ad74/32.png) [@arrbeejay](https://boards.straightdope.com/u/arrbeejay)\ **Post date:** [February 6, 2003, 8:55pm UTC](https://boards.straightdope.com/t/missing-exit/153215/14 "2003-02-06T20:55:23Z")
Wow, Toadspittle, that’s very cool! Thanks for the info. ---
**Author:** ![JeffB](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jeffb/32/188_2.png) [@JeffB](https://boards.straightdope.com/u/JeffB)\ **Post date:** [February 6, 2003, 9:28pm UTC](https://boards.straightdope.com/t/missing-exit/153215/15 "2003-02-06T21:28:51Z")
> [@](#): > > \*Originally posted by brad\_d \* > Some states number their exits by mile marker (Texas and West Virginia, for example), and others number them consecutively (Pennsylvania). We’ve had a couple of threads about this, and I believe it’s pretty much a matter of state preference. There are pros and cons to each method, I suppose. Pennsylvania used to have consecutively numbered exits, but it has switched to mile markers. Info on the change-over is [here](http://www.pahighways.com/exits/). I still am not entirely used to the new system when I’m driving in PA. ---
**Author:** ![brad\_d](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@brad\_d](https://boards.straightdope.com/u/brad_d)\ **Post date:** [February 6, 2003, 10:07pm UTC](https://boards.straightdope.com/t/missing-exit/153215/16 "2003-02-06T22:07:57Z")
> [@](#): > > \*Originally posted by JeffB \* > **Pennsylvania used to have consecutively numbered exits, but it has switched to mile markers.** Thanks for that info - I hadn’t known about the switch. ---
**Author:** ![ltfire](https://avatars.discourse-cdn.com/v4/letter/l/7ea924/32.png) [@ltfire](https://boards.straightdope.com/u/ltfire)\ **Post date:** [February 7, 2003, 1:32am UTC](https://boards.straightdope.com/t/missing-exit/153215/17 "2003-02-07T01:32:19Z")
Drove to Tennessee a few years ago on Rt 80, I believe. Started to pick up signs for Roanoke, Va. about 100 miles before the exits for what I guess is a sizeable city. Every 10 miles another sign stated the distance left before arriving there…80 miles to Roanoke…70 miles to Roanoke…you get the picture.Finally reached a sign that said Next 3 exits…Roanoke. So help me as I write this, the next 3 exits were closed due to road work and that was that. So, as far as I’m concerned, there is no place named Roanoke, Va. and when iI see it as an address for something, I laugh and think ‘that’s a scam’. ---
**Author:** ![Zagadka](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zagadka/32/7272_2.png) [@Zagadka](https://boards.straightdope.com/u/Zagadka)\ **Post date:** [February 7, 2003, 1:40am UTC](https://boards.straightdope.com/t/missing-exit/153215/18 "2003-02-07T01:40:06Z")
… I’ve always wondered why the hell you easterners are so all over numbering highways, while here in California it virtually doesn’t exist… It seems logical and all, but we never have any problems without it… ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [February 7, 2003, 1:49am UTC](https://boards.straightdope.com/t/missing-exit/153215/19 "2003-02-07T01:49:43Z")
> [@](#): > > \*Originally posted by Trinopus \* > \*\*It isn’t even consistent within a state… If you drive east from Fresno, California (which I do as often as I can!) the roads are named for their distance from the center of town, i.e., Road 42 is 4.2 miles out. But that’s the only place I’ve ever seen that does it that way! > > Trinopus \*\* OK that explains the road 42. But could somebody explain the exit sign for Seventh Standard Road up near Fresno? Are the other 6 irregular? ---
**Author:** ![Duke](https://avatars.discourse-cdn.com/v4/letter/d/e8c25b/32.png) [@Duke](https://boards.straightdope.com/u/Duke)\ **Post date:** [February 7, 2003, 4:29am UTC](https://boards.straightdope.com/t/missing-exit/153215/20 "2003-02-07T04:29:51Z")
Before PA switched over to mile-marker exit numbers, I-81 had a “missing” exit number near Harrisburg. The intent of the highway planners had always been to extend PA-581 to the interstate, but, after they built I-81, replete with exit ramps and signs, they didn’t have 581 built out that far. So for years, there was a “phantom exit,” one that I remember well on our family trips down to Virginia. Eventually (sometime in the '90s?), the PA-581 extension was completed. It looks like from the link provided by **JeffB** that the “missing number” was 16, now exit 59. [Next page](https://boards.straightdope.com/t/missing-exit/153215.md?page=2)