On 02/03/2011 02:25 PM, PJ Houser wrote: > Hi all, > > I have some basic questions: > > 1) Why are relations preferred for bike routes?
Relations are preferred for /all/ routes, actually. This is because the attributes of said route span unique ways. For example, only parts of Marine Drive in Portland are part of the 40 Mile Loop cycleway, and across town, most but not all of the Springwater Corridor is part of 40. Likewise, many routes may use the same way, but don't share attributes with other routes on the same way. An example of this would be US 30 and I 84, which frequently share ways, but don't share ways for the entire length, and have radically different attributes associated with each route. Or, say, Martin Luther King, Junior Blvd in Portland: It's both a road route (OR 99E) and a bus route (TriMet 6). Likewise, tagging route attributes on ways causes tagging collisions (as we're experiencing with road routes now): underlying ways often have refs that belong to them (like bridge numbers) but not the route itself. Then there's rendering. Road routes aren't particularly of interest if you're generating a bus map from OSM, for example. Likewise, foot routes are useless to truck drivers (You wouldn't expect a big rig on Metro's "4T" trail, would you?). Using relations for route data makes custom renders much easier. > 2) In the database, how do relations apply to ways? The attributes > associated with a relation - how are they tied to ways? Relations are essentially "tags" on a way, as most editors view them. > Will routing software use the attributes in a relation to determine if a way > is suitable? Depends on the routing engine. > 3) In Portland, Oregon, we have an interconnected series of unnamed bike > boulevards - how should we split these into relations? There are > different tiers of bike boulevards (low traffic, middle traffic, bike > lane, cycletrack, traffic calming devices but no bike lane, etc). Should > we make a relation out of all connecting and similarly tiered ways? It'd > be easier to just add attributes to the ways, but the OSM wiki seems > quite clear on bike routes as relations. Bike boulevards are on the same network as each other (well, the Portland ones, are, at any rate; note I'm not referring to official routes for state highways like 99 or federal highways like 205 or 84 since you're talking about city bike boulevards). You're confusing attributes that belong to the way (cycleway=lane, cycleway=track) with those that belong to the route (network=lcn).
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