Pondering Interstate Highways
I thought I basically had the interstate numbering system figured out, but I wasn't aware that you could have 2 highways with the same number in different parts of the country. An example, I-84 star...
Forum Discussion
There is a ranking of numbers. The 10s and 5s were used for cross country runs, at least to the extent it made sense. Other even numbers were used for partial runs WE runs, and odds for NS. Where possible numbers are used in consecutive order (small to the south and west). As your example shows, it's not against the rules to have discontinuous segments, though those mostly are the result of name changes.
In the East I see 84, 86 and 88 between 80 and 90. I don't seen an 82. In the west there's 86, 84 and 82. Given that there are only 4 choices between 80 and 90, so sort of reuse was inevitable.
On further thought, 20, 30, 50, 60, 70 don't make it to California.
http://en.wikipedia.org/wiki/Interstate_84_(Oregon%E2%80%93Utah)
I84 was originally I80N, branch of I80 serving the PNW. The name change was in 1980, following a change in policy regarding the letter suffix like 'N'.
http://en.wikipedia.org/wiki/Interstate_82
The change to I84 put the numbering of I82 out of place (north of a larger number). I82 was originally planned to follow US12 to Tacoma, and there was even talk going south in Oregon along US97.
http://en.wikipedia.org/wiki/Interstate_86_(west)
I86 in Idaho was originally I15W. Again a name change to eliminate the letter suffix, even it meant 'duplicating' numbers elsewhere. I15E in southern California became I215.
Curious fact - there is now a I2 - a short segment in the lower Rio Grande valley.
In the East I see 84, 86 and 88 between 80 and 90. I don't seen an 82. In the west there's 86, 84 and 82. Given that there are only 4 choices between 80 and 90, so sort of reuse was inevitable.
On further thought, 20, 30, 50, 60, 70 don't make it to California.
http://en.wikipedia.org/wiki/Interstate_84_(Oregon%E2%80%93Utah)
I84 was originally I80N, branch of I80 serving the PNW. The name change was in 1980, following a change in policy regarding the letter suffix like 'N'.
http://en.wikipedia.org/wiki/Interstate_82
The change to I84 put the numbering of I82 out of place (north of a larger number). I82 was originally planned to follow US12 to Tacoma, and there was even talk going south in Oregon along US97.
http://en.wikipedia.org/wiki/Interstate_86_(west)
I86 in Idaho was originally I15W. Again a name change to eliminate the letter suffix, even it meant 'duplicating' numbers elsewhere. I15E in southern California became I215.
Curious fact - there is now a I2 - a short segment in the lower Rio Grande valley.
