My apologies.  Its just too easy to get into the habbit of using jargon and
acronyms.

TRO =
Traffic Regulation Order.  This makes it illegal to exercise a right that
exists over a lane.  Example sign:
http://www.highwaycode.gov.uk/sign049.htm

UCR=
Unclassified County road.  These are sometimes shown as ORPA (Other Route
with Public Access - see the key on Ordnance Survey Landranger and Explorer
maps).

RUPP=
Road Used as a Public Path.  This is a highway is recorded on a Highway
Authorities Definitive Map of public rights of way and usually has public
rights for motor vehicles - but it mainly used by walkers, cyclists and
horse riders.   These are usually, but not always, unsealed - i.e. no
tarmac.

BOAT=
Byway Open to All Traffic.  This also is a highway recorded on a Definitive
Map.  It always has public rights for motor vehicles - but again is mainly
used by walkers, cyclists and horse riders.   Again, these are usually, but
not always, unsealed.

NERC=
Natural Environment and Rural Communities Bill.  This is legislation that is
currently going through parliament - i,e, it is not yet law.  You can read
about it here:
http://www.publications.parliament.uk/pa/ld200506/ldbills/023/2006023.htm

If the NERC Bill is passed in its current form, the Rights of Way section
(s61 & s62) will extinguish vehicular rights over all unsealed roads EXCEPT
BOATs and UCRs (providing they are not also recorded as footpath, bridleway
or RUPP on Definitive Maps).   Effectively, it will wipe away well over half
of all green lanes for vehicular traffic.  The powers being given to
National Parks could well wipe away much of the other half.

You might find the following sites interesting:
http://www.glass-uk.org
http://laragb.org
http://www.trf.org.uk

I hope this helps

Cheers
Andrew