This needs to be set with turn restrictions or permissions on the track. There are places in the western US where there are legal turns directly from a motorway onto what would probably best be classified as tracks, including a few actual crossroads, such as at http://www.openstreetmap.org/?lat=31.1514&lon=-105.2699&zoom=14
On Fri, Oct 10, 2008 at 09:33, Jon Bright <[EMAIL PROTECTED]> wrote: > Hi Frederik, > > Frederik Ramm wrote: >> >> I wonder if it would nevertheless make sense for routing engines to >> implicitly disallow leaving a motorway on anything else than a >> motorway_link (or at least not on something as small as a track). > > You'd certainly want to allow leaving a motorway onto trunk, primary and > secondary. Near where I live, the A46 (motorway) ends and turns into > the B326 (primary): > > http://www.informationfreeway.org/?lat=51.31285458075313&lon=7.27426070665261&zoom=17&layers=B0000F000F > > Something similar happens east of London, where the M25 (motorway) > becomes the A282 (trunk) for the Dartford river crossing: > > http://www.informationfreeway.org/?lat=51.48429693501172&lon=0.2717440463221352&zoom=15&layers=B0000F000F > > An example with secondary would be this bit of the A44: > > http://www.informationfreeway.org/?lat=51.32945959272296&lon=7.016253712974789&zoom=17&layers=B0000F000F > > My suggestion for a solution would be to explicitly exclude "track". In > theory, as you say, even this shouldn't be necessary. I don't think you > even need turn restrictions - as far as I'm aware, pretty much every > such track has access restrictions preventing its use as an exit. But > in practice, not everyone will have tagged everything perfectly, so > excluding "track" (and maybe also "unclassified") seems like a > reasonable compromise. > > (A more complicated and computationally intensive way of doing this > would be to disallow turns where the turn angle is greater than 45 > degrees from the motorway and the motorway itself continues. But I > think the better way to deal with that would be to analyse the OSM data > for such cases, produce a list and have "gardeners" enter appropriate > access or turn restrictions.) > > Another case you might want to think about while looking at this is > places like: > > http://www.informationfreeway.org/?lat=51.94166322328894&lon=7.553746825469445&zoom=15&layers=B0000F000F > > This is a normal rest stop on the motorway (between Münster-Süd and > Münster-Nord. The quickest way to reach some parts of Münster is to > leave the motorway at the rest stop, take the road leading off parallel > to the motorway and then join the K5. But it's also illegal to do so. > > Refusing ever to turn from a motorway onto highway=service might > therefore also be appropriate. > > Jon > > _______________________________________________ > Routing mailing list > [email protected] > http://lists.openstreetmap.org/listinfo/routing > -- David J. Lynch [EMAIL PROTECTED] _______________________________________________ Routing mailing list [email protected] http://lists.openstreetmap.org/listinfo/routing
