[mkgmap-dev] _link roads speed limit needs increasing

Fri Aug 3 01:12:16 BST 2012

Travelling down highway 32, then 329 in Thailand recently I was told to
do a U-turn, then use a dirt track, rather than the ramp that linked to
h'way 329. Try routing yourself in Mapsource or Basecamp at N14 27.106
E100 32.322. It should look like something in this pic:
https://dl.dropbox.com/u/30711166/OSM.T.jct.32-329-route.prob.jpg

The route chosen by both GPSr & Mapsource is actually longer than simply
following the ramp, but it avoids the ramps.

The ramps were drawn as secondary_link which in the Garmin map becomes
low-speed ramp with speedlimit 20 and RC=2.

The U-turn is a trunk_link => principal h'way, SL=90, RC=4.

The dirt track has SL=20, RC=0.

It looks like the Route Class is less important here than the SL: by
following the main route you only travel for a short distance over a
slow road (the track), whereas the ramps are quite long. Mathematically
this would make for a quicker trip.

To avoid people being routed off main highways I propose that ramps
mapped from secondary_link get the same SL as secondary and that the
speed limits on the other links are reviewed.

Regards,
Peter.