[OSM-talk] Roundabouts and routing

[SomeoneElse]

Thomas Davie wrote:
>
> Proposed solutions (all of which are horrible):
> 1) Don't tag sliproads onto roundabouts as junction=roundabout, 
> instead use some other tagging scheme.  Not greatly desirable because 
> it involves a *whole* lot of retagging.
> 2) Ask garmin to fix it (doesn't sound likely).
> 3) Write some fancy heuristics in the conversion from OSM to routable 
> garmin maps that figure out when you're looking at slip roads and when 
> it's an actual roundabout (sounds unreliable).
>

Would it be possible to include a link to an example roundabout in OSM?  
Within the UK there seems to be a variety of tagging approaches, 
everything from not tagging flares to tagging individual roundabout lanes.

I'm guessing that you're using an mkgmap-generated map, in which case 
there are options that alter roundabout handling (including the 
delightfully named "--frig-roundabouts").

The problem that usually gets me is miscounting exits (when two exits' 
adjacent flares share the same node), but late announcment of exit 
number can also be annoying.

By the way, if you are using mkgmap then you might want to have a look 
on http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev - that's where 
most mkgmap discussion takes place.

Cheers,
Andy