No DLR train ever operates without a member of staff being present.
They are known as PSA's (Passenger Service Agents).

They are responsible for operating the train - starting it (when safe
to do so and having closed the doors at stations and having received
the 'Ready to Depart' command. The automatic train control then does
everything else by commands from the signalling system including
'docking at the next station stop. Customer door open buttons are
released then the PSA repeats his actions for departure.

The PSA may be requested by Control to occupy the front position for
special rule purposes and even drive manually in certain circumstances
including refresher training and to get the train into and out of
depot sidings.

The PSA is also responsible for ticket checks and customer assistance
but their primary function is to keep the trains moving.

Richard Thomas