CIG's were introduced in 1963 and were initially allocated to the Brighton Mainline (C is corridor and IG was the telegraphic code for Brighton). The formation of a CIG was an innovation to the Southern Region as they only had one motor coach (with two power bogies) and it wasn't at the front of the unit. The formation was DTC+TSO+MSBO+DTC. Subsequent deliveries (phase 2) were introduced in 1970 on the Western division and later in the 1972 for the Central division and Reading lines both times withdrawing "COR" units. CIG's were never allocated to the Eastern division although after privatisation Connex took some CIG units from the Central division. CIG's have been reformed over the years. BIG's (which were CIG's with a buffet car replacing the TSO) were changed to either operate with a CEP trailer car instead of the buffet car or run without the buffet car which changed the classification of the units from BIG to COP (Corridor open plan). The COP's were put to work on the "Coastway" section of the Central division however this did not last and the COP's had a phase 1 TSO put back into the formation to basically make them back into CIG units.

At present CIG units survive on the Western and Central divisions. No phase one CIG's or COP's remain in service.

Click Here to view some photos of CIG's in action