The left/right/straight only works with 2 to 4 segments attached
AlanOfTheBerg wrote:In the latest example you gave, I'm not sure why you aren't getting a left/right prompt as those angles are quite close to 90 degrees. Unless the "angle" is calculated from the segment end-points. We haven't been given that level of detail. Here's how your angles look for segment end-to-end angles.
- and please note I used "segments", not "nodes", because as soon as you connect two segments to the same node of the roundabout, all hell breaks loose.
It's worthless to try to align 90º when 5 or more segments are attached. It will always say "take the nth".
Now on your 3rd example, you have two choices - either risk the exit/entry distance and ensure a straight/left/right well behaved roundabout, or not risk and keep the segments on the right GPS tracks. In other words, this roundabout is too dangerous to force a 4 way, as the entries and exist are really too far away.
If you really want to get the keep left, it's quite simple, just kill those Y splits near the roundabout and connect the 4 two-way segments into the middle, align at 90º and create the roundabout.
What I personally do is: if there are 2 to 4 segments, and the instructions are quite clear, I kill as much as possible any unsplited segment (two segments each one-way) nearby and surely always any Y nearby the roundabout, possibly faking the entry/exit point a little to ensure the 90º.
If the roundabout has 3 segments in 120º, or 5 or more, then I respect the GPS lines, still kill any irrelevant Y, but keep the Y in cases so far away like yours so the roundabout design is recognizable from the map.
I think it's more important to see on the map that for example the line coming from southeast to northweast is almost straight than having the keep straight instruction.