[Talk-us] Separate relations for each direction of US & State highways.

[Minh Nguyen]

On 01:11 2013-11-27, Peter Davies wrote:
> Martijn,
>
> I think it would be conceptually clearest for all the 2-way single
> carriageway ways to point the same way and would suggest that this
> should normally in be the direction of increasing milepoints/pointes
> kilometriques  (usually northwards or eastwards).  At Castle Rock we
> call this the positive travel direction (increasing linear reference
> values) while the decreasing milepoint direction (reducing
> milepoints/pointes kilometriques) we would call the negative direction.
> It would be great for us if OSM forward tied in with milepoint increases.
>
> Inevitably there is an occasional glitch in states such as Idaho where
> "DOT milepoints" actually reverse direction for sections of 2 or 3 state
> routes statewide, due to legacy signposting and route redesignation, but
> this is probably less than 1% of routes nationally. More common is minor
> milepoint jumps (where routes have been shortened by new construction)
> and minor milepoint repeats (where bypasses are longer than the original
> through route; a situation that Washington State calls backmiles and
> Caltrans calls formulas). Despite this, there is almost always a mostly
> consistent increasing milepoint (OSM potential PK tag) postive travel
> direction that could become OSM forward on 2-way single carriageways.

In Ohio, non-freeway reference markers reset to 0 at each county line 
along a route. As far as I can tell, though, the markers never count up 
in one county, then down in the next. So I suppose one carriageway could 
have increasing markers as it goes east across County A and continue to 
have increasing markers as it continues south through County B, as long 
as the route goes east-west overall.

It appears that freeway mile markers do not reset at county lines, but 
cardinal directions may. On loop freeways, the mile markers increase 
clockwise through all four cardinal directions. So traveling clockwise 
on I-275 (which goes around Cincinnati), the mile markers increase 
continuously, but the signposted direction is East in Hamilton County, 
South in Clermont County, and West upon reentering Hamilton County and 
in Northern Kentucky. I'd imagine the same thing applies to loop 
freeways in most states. (Or is there such a thing as 
"counter-clockwisebound"?)

-- 
minh at nguyen.cincinnati.oh.us