In the Interstate Numbering system, how do they determine the 1st number in auxillary 3 digit number ie ->?

I 294, or I 465, where does the 2 and the 4 come from?In the Interstate Numbering system, how do they determine the 1st number in auxillary 3 digit number ie -%26gt;?
It says what type of highway it is.





odd numbers, such as 1, indicate a spur into a city or place.. 190 in chicago is a spur into O'Hare





An even number such as 2 indicates a bypass or ';beltline';... and means that the highway reconnects to the main route. So, 294 would be a bypass along I-94, probably near a city, that reconnects with 94's route somewhere. 294 does just that, bows out from the South suburbs of Chicago... goes out along the suburbs, and reconnects to the north.In the Interstate Numbering system, how do they determine the 1st number in auxillary 3 digit number ie -%26gt;?
Odd numbers are spurs away from the intestate system. Even numbers are loops or bypasses that eventually reconnect with the interstate system.





Typically, they try not to repeat the same number in different places in the state, and they start with the lowest number, hence there are lots of 3-digit interstates that start with 1,2,3... but not many starting with 7,8,9. This is also why you might see a interstate change designation to a state highway when crossing state lines, because that number is already in use in another part of the state. Where a 3-digit interstate number does show up in multiple segments in the same state, it usually means they were meant to be continuous, and the middle part simply hasn't been built yet.