[OSM-newbies] Left: and Right: tags

[Philip Striplin]

Newbie question.

I can see that there are number of places where boundaries are marked 
with a left: and right: tag (for example, the county boundary near me is 
marked left:county=Worcestershire and right:county=Herefordshire.)

That's fine, but how do I tell my right from my left :)  In the case in 
question, the boundary runs almost exactly north-south at this point, 
which if I assume the normal north-upwards orientation, would have the 
county names reversed (Worcestershire actually being on the East - or 
right-hand - side of the line).

I'm guessing the answer is that there is a "direction" to the boundary 
line which tells me which way I'm facing, and so determines which side 
of the line is "left", but I've not been able to find out how to find 
this direction.  Could someone help, please?

And - supplementary question: the reason I'm asking is that I want to 
include the boundaries of my local parish, which shares the county 
boundary for quite a bit.  I presume that to do this I select the bit of 
the county boundary I need to use (adding nodes if required to show the 
places where the county and parish boundaries diverge) and add them to a 
new relation along with the bits of the boundary I'm going to have to 
draw to collect all the bits of the parish boundary into a single set.  
Or am I on the wrong track here?

Thanks.