[Tagging] Access restrictions and expressway=yes

Minh Nguyen minh at nguyen.cincinnati.oh.us
Sat Feb 20 20:50:58 UTC 2021


Vào lúc 12:39 2021-02-20, Minh Nguyen đã viết:
> Conventionally, U.S. road maps distinguish between "expressways" 
> (limited-access or partially controlled-access roads) and "freeways" 
> (controlled-access roads) with a different color and/or line pattern. 
> [2] (The term "limited-access" refers to the presence of abutters and 
> at-grade intersections, not access keys like foot=*.) Unlike in other 
> countries, the distinction between expressways and freeways is not 
> consistently expressed by law or signage, and it also doesn't neatly 
> align with the global highway=* definitions in OSM, especially when it 
> comes to substandard roads.
> 
>  From a traffic engineering standpoint, an expressway differs from a 
> surface street by meeting most of these criteria:
> 
> * Designed for high speeds (doesn't necessarily have a high speed limit)
> * A dual carriageway
> * Frontage roads consolidate driveway access
> * A mix of ramps and at-grade intersections
> 
> An expressway doesn't meet all the criteria of a freeway, for example by 
> having a few signalized or unsignalized intersections with cross 
> streets. An expressway may be a relic of an older time before freeways, 
> a political compromise between motorist and environmental interests, or 
> a surface street being gradually upgraded to a freeway in stages as 
> funding allows.

I should point out that usage of highway=trunk in the U.S. is often 
based on similar criteria, since there isn't an obvious definition of a 
trunk road in the U.S. But we've endured years of edit wars between 
ardent road classificationists because some expressways are far too 
short or insignificant to be tagged as highway=trunk. expressway=* is 
one approach to resolving the disagreement, but it's imperfect for other 
reasons -- namely, that it lacks support from data consumers.

-- 
minh at nguyen.cincinnati.oh.us




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