pgRouting returns the edges as they are stored in the database and not 
as traversed, so on some edges the direction (from-to or to-from) needs 
to be flipped around.

This script returns all segments in the correct direction.

A note about line 59: this script assumes that pgRouting returns the 
segments in the correct order, which means that either the condition 
from line 50 or from line 52 evaluates to true. So, line 59 should 
never be executed. However, some people have reported on the 
pgrouting-users mailing list that the segments returned from 
pgRouting are not in the right order — in which case you would see 
the message from line 59.