This new relation (type through_route) specifies which 2 ways are the "through route" at a junction. The relation requires 2 ways (no role required) and a node with role = junction. It should only be used at those junctions where the through route cannot be reliably inferred from the ways' names and/or refs. Here's an example from my local town: | 1 | / | / |/ A | | | | B /| / | / | 2 | The vertical road is the "through route", i.e. you can drive from one end to the other without crossing any white lines. But, from point 1 to point 2 is a B road so ways 1-A, A-B, and B-2 all have some ref, say, B1234. Without the through_route relation, mkgmap assumes (erroneously) that the through route is 1-2 because all of the ways in that route have the ref B1234. By adding 2 through_route relations (one at A and the other at B), mkgmap is informed of the real through route and will take that into account when adjusting the turn headings. The end result is that the quality of the routing directions is improved (we hope). In this example, we need to have 2 relations because the B road joins/leaves the through route at two places. So if you know of any junctions that would benefit from this relation, please add it to the map data and try this patch to see if it improves the routing instructions. Mark