[thanksforcoming]

Having grown up and Oregon and lived in Los Angeles for the past 7 years -- up north it would be "I took I-5 from Seattle to Portland" while in L.A. it would be "I took the 5 from Seattle to Portland." Neither dialect uses just the number on its own.

True for more than just single digit numbers too, e.g. I-205 vs. the 405.

[int_19h]

Here in WA, it seems that for single- and double-digit numbers, people usually prepend the prefix - so it's also I-5, not just 5; and I-90, not 90.

But for multi-digit, it's virtually never there - it's 405 and 520 (without "the"!), not I-405 and WA-520.

Now that I think about it, it's probably not so much about the number of digits, as it is about the number of words. So I-90 gets the prefix because "ninety" is a single word, but I-95 somehow sounds strange.

[spc476]

Up in Detroit (I have family there) almost everyone talks about 75 (I-75). Down here in South Florida (where I live), it's always I-95. Just "95" sounds strange to me, as well as "I-75".

I guess it's what you grew up listening to.

[ChuckMcM]

In the Bay Area, between those two, what I often hear is "I took 101 to San Francisco" or "101 was mobbed so I took 280" or "did you come down 85 or 280 to 101?" no 'i' no 'highway' no definite article.