[Talk-us] Freeway directions

Tod Fitch tod at fitchdesign.com
Fri Oct 18 03:52:36 UTC 2013


On Oct 17, 2013, at 6:11 PM, Nathan Mills wrote:

> On 10/17/2013 1:03 PM, Richard Welty wrote:
> 
> If my GPS tells me to "turn right at the entrance to East Interstate Whatever" and the sign says "North Interstate Whatever," I'm going to be confused and wonder if I'm actually making the correct turn. Even more so if it's a printed list of directions.
> 

I can't say for the urban auxiliary (three digit) freeways, but the single and double digit Interstates all seem to have on ramp signs that use their nominal direction rather than the compass direction at that particular location. At least that is my understanding from what I've read about the rules and conventions that are supposed to be used and I have never noticed an exception.

For what it is worth, it is my understanding that within a state the use of a particular number, at least outside of triple digit urban beltways and penetration Interstates, is supposed to be unique. So if I-10 goes through your state, there will be no US10 nor a state highway 10. I haven't paid much attention to this in other states I've visited but it seems to hold true for California. If true throughout the US then it could be used to help validate highway route numbers.

Confusion in California comes in two flavors: In Southern California there is a popular tendency to call freeways by a name (e.g. "The Ventura") and use the actual direction the road goes for that named segment (east/west for the Ventura) when giving directions. But the named segment might be on a US or Interstate with a different nominal direction. This bit me years ago when we were mailing out wedding directions and I assumed the on ramp from the hotel area would be labeled for the eastbound Ventura Freeway when, upon checking, it turned out to be labeled for southbound US101.

In the San Francisco Bay Area the confusion comes from the fact that the only Interstate to enter the area is I-80. So all the urban auxiliary (three digit) freeways have to have a suffix of 80 (even number implying east/west) even if the road is north/south. So we have 280, 580, 680, 880, etc. all going in different directions. Southern California avoids this by having I-5, I-8, I-10 and I-15 enter the area, so I-210 is basically east/west while I-405 and I-215 are basically north/south.

-Tod


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