[Talk-us] Freeway directions

Nathan Mills nathan at nwacg.net
Fri Oct 18 01:11:10 UTC 2013


On 10/17/2013 1:03 PM, Richard Welty wrote:
> hmmm. we're using exit_to (i think) for off ramps, maybe we need
> entrance_to for on ramps
>
> the value would be more or less exactly the text visible on the
> signage.
>

This makes the most sense to me as the solution for the specific use 
case Martijn is asking about, where the tag value will be used as the 
basis for generating directions which the user will expect to be 
consistent with signage. The directional tag on a wayfinding sign at the 
motorway entrance may or may not correspond to the bannered direction of 
the route or route segment.

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.

Being able to include control cities as well as cardinality is a nice 
bonus, also.

FWIW, I have in the past typically done one relation for both directions 
with the bannered cardinal direction in the segments' role tag, if it is 
bannered, or forward/reverse otherwise. I settled on that for my own 
work because it plays well with non-motorways that are sometimes divided 
and sometimes not. There's not really any logical reason two relations 
and a super relation couldn't be used in that scenario. It just seems 
somehow less elegant to me to have the extra relations when most of the 
route is undivided.

-Nathan



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