LU Stock Question

[Class86Fan]

Why do some LU Stock have 3 driving cabs?

 

[jopsuk]

Because some of the trains are formed of three "single ended" units- for instance, the C-Stock is formed of three pairs of driving-motor and unpowered-trailer cars. Gives the ability to split and change formations, just need to make sure you end up with a cab at both ends. Some other stock types are formed of two double-ended units- though some of these might have had cabs effectively "deactivated" (these aren't painted red) such as many of the A-Stock units.

Even the S8 and 2009 stock is technically formed of two single ended 4-car units, with the formation being able to be easily split in half as required on depot.

 

[Mutant Lemming]

With 73 stock on the Piccadilly they needed six car sets for the main service and 3 car sets for the Aldwych shuttle. So as not to have a big gap between doors in the middle of a six car train you would get an UNDM (uncoupling non-driving motor car) on a single ended set to couple to a 3 car set.