On Sun, 04 Jul 2010 19:21:36 -0700, Alan Mintz wrote: > At 2010-07-04 13:41, Alan Millar wrote: >>How are people using the "lanes" tag on motorways? Do you count the >>on/off ramps that come and go? > > Generally, no. > > >>On a lot of the freeways near me, they have two main driving lanes on >>each direction, so I set it up as a dual carriage way with one-way on >>each side, and mark each side as lanes=2. >> >>The question comes in for the on/off ramps. There are sections where >>two intersections are somewhat close together, and so there is an on- >>ramp, a long extended merging lane, then the next off ramp. Strictly >>speaking, there is a third lane for some distance between the the ramps, >>but it isn't a "through" lane. There are only 2 driving or through >>lanes in that section of freeway. >> >>See for example hwy 217 between Denney and Allen at: >> >>http://www.openstreetmap.org/? >>lat=45.473345&lon=-122.786743&zoom=18&layers=B000FTT > > I generally, form the intersection of the ramp with the main roadway at > the point where the solid line starts or ends - the first place you can > legally merge from an onramp or the last place to an offramp. In this > case, this leaves too short a section of 3-lane main roadway to bother > breaking it just in order to tag that short section with the extra lane. > I see the lanes tag being useful primarily in determining likely speed > possible in making routing decisions, other factors being equal. It > could also be useful in rendering. Neither would seem to sway me to add > the extra lane for such a short distance. > > I-10 in this area > http://www.openstreetmap.org/? lat=34.03753&lon=-118.280316&zoom=18&layers=B000FTF > might end up being an exception in some places (I didn't look closely, > but it comes to mind). > > >>I have only been counting the driving or through lanes, so I have tagged >>this as lanes=2, and just ignored the short extent of the extra merging >>lane. > > Agreed. > > >>Likewise, there are suburban streets that have an extra turn lane just >>before an intersection, like Murray Blvd at: >> >>http://www.openstreetmap.org/? >>lat=45.4814&lon=-122.8261&zoom=18&layers=B000FTTT >> >>As one big street with two driving lanes each direction, I've tagged it >>as lanes=4 and ignored the short extent of the extra turn lane. > > Because that center lane is present between intersections as a center > turn lane, I tag lanes=5. This, to distinguish it from roads where there > are only 4 lanes (2 in each direction) for the stretches between > intersections, since left turns without that center turn lane cause more > congestion (again thinking of speed estimation).
I tend to discount restricted, merging and turn lanes myself, and count restricted lanes as a seperate way as a stop-gap measure until lane restrictions are more or less sorted. I wish I had a better tagging solution than that, since a lot of interchanges in Portland are behind blind curves in no-lane-change sections. _______________________________________________ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
