[Openstreetmap] How to draw complex roads?

[Petter Reinholdtsen]

When drawing Oslo, I ran into a few problems.

How should I draw complex roads?  The city have roads in multiple
levels (for example main road in tunnel and crossing on the surface),
and I have no way to document the relative elevation of a road.  Any
idea how I should handle this?

Another problem is how to draw the main roads, with several lanes in
each direction, and a physical separation between the lanes going in
opposite directions.  As we are currently only drawing center lines, I
guess I could draw these main roads as a single line.  But on the
other hand, it is not possible to cross the road, the route finding
algorithms would be fooled if I did this.  Here is an example of the
road layout:

         A
         |        _
    -<---+-------+ \
  D              |C +--<->-
    ->---+-------+_/
         |
         B

The main road starts at the road-about in C, and continues towards D.
Road A enters on one side of the main road, and continue as road B on
the other side.  There is no way to cross the road directly from A to
B, one need to drive through C to get from A to B.  How should I draw
this?  How are other people drawing this?  It is hard to draw the two
lanes accurately with the GPS points available.  The distance between
the lines are just a few meters, less then the GPS accuracy.