4 ms·

Yes, and this even happens with major highways! I'll be trying to pick a ~200-mile route, and I have to play zooming gymnastics just to see the difference betwe

Yes, and this even happens with major highways! I'll be trying to pick a ~200-mile route, and I have to play zooming gymnastics just to see the difference between I-84 and I-95! Okay, I should just know the difference with roads that big. And okay, generally East/West interstates use even numbers representing what % of the country lies to the South while North/South use odd numbers representing what % lies to the West. But I shouldn't have to know that when I'm wondering how to avoid the accident on "that big yellow stripe that passes through D.C." Sometimes I'll use a mapping app designed for outdoors activities, because it is so much easier to read than Google Maps.

amadeusw 7y ago
I had no idea about the interstate numbering system. This is awesome to know, thanks.
- munificent 7y ago
  It's a cool system. The numeric rules are (though there are lots of exceptions): * Primary interstates are one or two digits. Shorter spurs, loops, and connectors are three-digits. * East-west primary interstates are even-numbered, north-south are odd. * Major arterials are divisible by five. (The longest interstates are I-90, I-80, I-40, I-10, I-70, I-95, and I-75.) * Odd routes increase in number going from west to east. * Even routes increase in number from south to north. * The last two digits of a three-digit interstate usually identify its main parent interstate. (For example, the I-310 spur connects I-10 to US 90.
  - whyaduck 7y ago
    Even routes increase from south to north (e.g. I-10 runs through Arizona, I-90 runs through Washington).
    - munificent 7y ago
      Oops, fixed.
- mynameisvlad 7y ago
  Another fun tidbit is that any 3-digit interstate is an auxiliary route of the 2/1-digit mainline. The first digit determines the type of route, with odd being a spur and even being a bypass or beltway. So I-405 is a bypass of I-5, and I-110 is a spur off I-10 connecting it to the Port of LA.
  - wahern 7y ago
    I-110 is also a spur connecting I-10 to downtown Pensacola, FL, Biloxi, MS, and downtown Baton Rouge, LA. And apparently there's a I-405 in Seattle. (All the I-110 spurs I've driven on.)
aphextim 7y ago
Thank you I had no idea how the numbers were chosen until now!
lotsofpulp 7y ago
> And okay, generally East/West interstates use even numbers representing what % of the country lies to the South while North/South use odd numbers representing what % lies to the West. The idea that the highways are designed and numbered to represent the proportion of land area of the contiguous US seems specious. Source? Edit: the interstate highway going north from Kansas City is 29, but obviously much more than 29% of the US is west of I-29.
- alexhutcheson 7y ago
  The semantics aren't exactly meant to be "% of land area", but they do represent a rough coordinate system[1], from (5, 8) in the SW corner of the contiguous US (San Diego) up to (95, 90) in Boston. Interestingly, US highways follow the opposite system[2], going from (1, 2) in the NE corner of the country (Maine) to (former) (101, 80) in San Diego. [1] https://en.wikipedia.org/wiki/Interstate_Highway_System#Numbering_system https://en.wikipedia.org/wiki/Interstate_Highway_System#Numb... [2] https://en.wikipedia.org/wiki/United_States_Numbered_Highway_System#Numbering https://en.wikipedia.org/wiki/United_States_Numbered_Highway...
  - lotsofpulp 7y ago
    Numbering from west to East and south to north and using evens and odds to mean East-west and north-south makes sense. But that doesn’t imply anything about proportion of country, however the measurement is defined.
  - jimktrains2 7y ago
    Those us routes came first and the interstates are purposely numbered backwards of it to avoid confusion.
- leggomylibro 7y ago
  Sure it's anecdotal, I just heard it from my parents as a kid. And obviously it's not exact, just look at how close I-94/I-90 are around North Dakota and compare it to I-90/I-80 or I-80/I-70. And a lot of the "East-West" interstates go diagonally or even North-South in places. But I doubt they made the roads by laying rulers across the map (except maybe in Kansas or Oklahoma), and it does seem like they generally increment from 0-100 in each direction with odd/evenness decided by the primary axis. Wikipedia has a lot to say on the matter, but I got bored reading all the special cases like how they number loops that connect two highways: https://en.wikipedia.org/wiki/Interstate_Highway_System#Numbering_system https://en.wikipedia.org/wiki/Interstate_Highway_System#Numb...

amadeusw 7y ago

I had no idea about the interstate numbering system. This is awesome to know, thanks.

munificent 7y ago
It's a cool system. The numeric rules are (though there are lots of exceptions): * Primary interstates are one or two digits. Shorter spurs, loops, and connectors are three-digits. * East-west primary interstates are even-numbered, north-south are odd. * Major arterials are divisible by five. (The longest interstates are I-90, I-80, I-40, I-10, I-70, I-95, and I-75.) * Odd routes increase in number going from west to east. * Even routes increase in number from south to north. * The last two digits of a three-digit interstate usually identify its main parent interstate. (For example, the I-310 spur connects I-10 to US 90.
- whyaduck 7y ago
  Even routes increase from south to north (e.g. I-10 runs through Arizona, I-90 runs through Washington).
  - munificent 7y ago
    Oops, fixed.
mynameisvlad 7y ago
Another fun tidbit is that any 3-digit interstate is an auxiliary route of the 2/1-digit mainline. The first digit determines the type of route, with odd being a spur and even being a bypass or beltway. So I-405 is a bypass of I-5, and I-110 is a spur off I-10 connecting it to the Port of LA.
- wahern 7y ago
  I-110 is also a spur connecting I-10 to downtown Pensacola, FL, Biloxi, MS, and downtown Baton Rouge, LA. And apparently there's a I-405 in Seattle. (All the I-110 spurs I've driven on.)

aphextim 7y ago

Thank you I had no idea how the numbers were chosen until now!

lotsofpulp 7y ago

> And okay, generally East/West interstates use even numbers representing what % of the country lies to the South while North/South use odd numbers representing what % lies to the West. The idea that the highways are designed and numbered to represent the proportion of land area of the contiguous US seems specious. Source? Edit: the interstate highway going north from Kansas City is 29, but obviously much more than 29% of the US is west of I-29.

alexhutcheson 7y ago
The semantics aren't exactly meant to be "% of land area", but they do represent a rough coordinate system[1], from (5, 8) in the SW corner of the contiguous US (San Diego) up to (95, 90) in Boston. Interestingly, US highways follow the opposite system[2], going from (1, 2) in the NE corner of the country (Maine) to (former) (101, 80) in San Diego. [1] https://en.wikipedia.org/wiki/Interstate_Highway_System#Numbering_system https://en.wikipedia.org/wiki/Interstate_Highway_System#Numb... [2] https://en.wikipedia.org/wiki/United_States_Numbered_Highway_System#Numbering https://en.wikipedia.org/wiki/United_States_Numbered_Highway...
- lotsofpulp 7y ago
  Numbering from west to East and south to north and using evens and odds to mean East-west and north-south makes sense. But that doesn’t imply anything about proportion of country, however the measurement is defined.
- jimktrains2 7y ago
  Those us routes came first and the interstates are purposely numbered backwards of it to avoid confusion.
leggomylibro 7y ago
Sure it's anecdotal, I just heard it from my parents as a kid. And obviously it's not exact, just look at how close I-94/I-90 are around North Dakota and compare it to I-90/I-80 or I-80/I-70. And a lot of the "East-West" interstates go diagonally or even North-South in places. But I doubt they made the roads by laying rulers across the map (except maybe in Kansas or Oklahoma), and it does seem like they generally increment from 0-100 in each direction with odd/evenness decided by the primary axis. Wikipedia has a lot to say on the matter, but I got bored reading all the special cases like how they number loops that connect two highways: https://en.wikipedia.org/wiki/Interstate_Highway_System#Numbering_system https://en.wikipedia.org/wiki/Interstate_Highway_System#Numb...