Anyone know why they skipped 50 and 60 when giving out the numbers?
Did they plan to add them later? Or did they want to go from 10 to 90 to match up with going from 5 to 95 on the north-south routes.
I guess there are no other areas where the Interstate numbers are similar to existing roads ?
There may be, but as a matter of general policy, you need to allow for people giving directions like, “Go south a bit, then turn west on route 70,” without people having to worry whether “70” is an interstate, a US highway, a state road or a county road.
By and large that’s true. The US highway system has low numbers in the east or north and increasing as you move west or south. Even numbers are for east west highways; odd numbers are for north-south highways. The interstate system used the same east-west, north-south divide, but the opposite ordering to keep numbers away from the same number in the other system. 50 and 60 are near the midpoint.
I recall reading that when the US Interstate numbers were assigned, no state could have a conflicting state or US highway number in it.
The US Highway numbers ran opposite the US Interstate numbers (i.e., higher numbers at southern latitudes and western longitudes for US Highways).
In California, for example, we had US Highway 80 that served San Diego until I-80 was created, serving San Francisco. US 80 was stripped of its number in the state to avoid numbering conflict.
OldGuy:
Yeah, but so are 45, 55 and 65 (not to mention other non-multiple-of-10 numbers within the middle range of the first hundred numbers) and there are interstates with those numbers.
According to the link below:
http://www.gbcnet.com/ushighways/history/1964_hwy_renumbering_contents.html
So, it looks like they skipped I-50 and I-60 so they wouldn’t have to renumber US 50 and US 60.
Interstate 70 and US 50 exist together in Utah, Colorado, Kansas, Missouri, Illinois, Indiana, Ohio, West Virginia, and Maryland. That would be a lot of renumbering.
I think the system for US highway numbers was not as strict. Here is NC we have US 1 and US 17 but also US 301 and 441. I-95 follows near US 301 here in NC.
That’s hardly the most confusing part about NC highway numbering…check this out. Yep, that’s I-74 and US-74, not just near each other but part of the same road.
So, if you live in NC, I can understand why it would be confusing to you that there wouldn’t be an I-50 or an I-60 just because they would be near a US-50 or US-60. Obviously, that potential problem didn’t seem to bother AASHTO in your neck of the woods.
I-74 is very new so maybe they forgot the old rules?
The “Interstate 60” name was reserved for the Trans-Canadian Highway when the takeover is complete. The number will represent the new number of states.
There’s 50 US states and 13 provinces and territories in Canada…I guess three of them will just have to become part of Neo Mexico.
It should be noted that the I-80 and US 80 conflict was resolved by California, during a massive reorganization of numbering that took place in 1963-64. While the AASHO guidelines would generally disfavor having two federal routes with the same number in the same state, it’s not impossible to have that (witness US 74 and I-74 being the same freakin’ road near to where I live!). But California decided to rationalize the whole thing in order to accomplish the spirit of the guidelines.
There were other issues involved in California’s numbering scheme. The upshot of the whole thing was a fairly rational result, although those of us who grew up with signage from the old scheme replaced by signage from the new scheme had some adjusting to do.
ETA: I think the “they didn’t use I-50 or I-60 to avoid conflicts with US 60 or US 50” idea is retroactive rationalization. Had they needed to use the Interstate numbers in question, they could easily have done so, and then re-signed the US routes. Or they could simply have designated US 50 as Interstate 50, for example. The plain fact of the matter is they didn’t need to bother, because they didn’t plan on having any added major coast-to-coast interstate highways. The fact that the country is fairly narrow from North to South obviated the need for 9 different “major” East-West interstates. The Rockies get in the way as well. You will note that I-20 and I-30 are relatively short, and don’t really end up having to go much past Texas to accomplish their goal.
[del]Isn’t it the other way around? I-95 is the main North-South route on the East Coast, while I-5 is on the West Coast, and I-80 goes from NJ to CA and I-10 from FL to CA.[/del]
Never mind. Now I see that you weren’t referring to the Interstate Highway System.
It will all work out when we allow Mexico to reclaim CA, AZ and NM! 
Good idea!