BR - British Railways Board ("British Rail")
ATW - Arriva Trains Wales Ltd./Trenau Arriva Cymru Cyf.
AXC - Arriva CrossCountry
c2c - c2c Rail Ltd.
CLR - Colas Rail Ltd.
CR - Chiltern Railways Ltd.
Crossrail - MTR Corporation Limited
DB - DB Schenker Rail (UK)
DCR - Devon & Cornwall Railways Ltd.
DRS - Direct Rail Services Ltd.
ECR - East Coast Railways Ltd.
EMT - East Midland Trains Ltd.
EUKL – Eurostar UK Ltd.
FCC - First Capital Connect
FGW - Great Western Trains Company Ltd.
FHT - Hull Trains Ltd.
FSR - ScotRail Railways Ltd.
FTPE - TransPennine Express Ltd.
FL - Freightliner Ltd.
GA - Greater Anglia
GBRf - GB Railfreight Ltd.
GCR - Grand Central Railway Ltd.
GTR - Govia Thameslink Railway Ltd.
HX - Heathrow Express Operating Company Ltd.
LM - London Midland
LO - London Overground Rail Operations Ltd
MD - Mendip Rail
ME - Merseyrail Electrics (2003) Ltd.
NR - Network Rail
NRL - Northern Rail Ltd.
NYMR - North Yorkshire Moors Railway
RV - Riviera Trains
SE - Southeastern Railway
SN - New Southern Railway Ltd. ("Southern")
SWT - South West Trains Ltd.
VWC - Virgin West Coast (Virgin Trains Ltd.)
WCRC - West Coast Railway Company