Dealing with signal failures// other incidents

A handful of Network Incident Response Managers driven by British Transport Police officers (also trained as medics) are strategically placed to respond in a marked police vehicle to certain disruptive incidents where the flow of passengers is seriously disrupted and trains stalled away from stations.

From our side they can be more of a pain and a little knowledge from previous failures is dangerous as some bad decisions have taken place in the past.

The vehicle shown is an 'ordinary' ERU vehicle driven by a member of the ERU Team.
The BTP driven vehicles have different markings and blue lights:

London Underground ERU 2593 by Ken, on Flickr

these Mercedes vehicles are now being replaced with new Volvo FLs:

It's an interesting one. I would have thought that they are still the same number of trains available, and the same number of drivers. So the logic would imply that the same service can be run as long as the trains and drivers can take the disruption rather than the fare-paying public.

The problem is that neither trains nor drivers are completely interchangeable.
Trains have maintenance schedules and things like that so, as far as possible, they need to end up where they were planned to, and if you have the wrong number of trains at each location you'll have delays at the start of traffic tomorrow. At the basic end, trains need to have checks done every 24 hours so a train that started the day in sidings needs to end the day at a depot. Heavier maintenance may also require a specific depot. If you are running a mixed fleet of trains this is even more complicated as you need to have the right number of each type at each location (and not every location can necessarily handle every type of train). This means that even though it might seem very simple to turn train 9 into train 19, you will have to shuffle things again later on if train 19 finishes its day at e.g. Parsons Green sidings but the unit involved is due its 14-day exam at Upminster Depot.

Drivers are even less flexible, as they have a limited amount of time they can drive for (in one stretch and in total) and as soon as that is exceeded they have to take the train to the first safe place to stop (if that isn't where they currently are) and can't take it any further. This could be very much in the way of other things so controllers will try to avoid drivers running out of hours if at all possible. They also need end up at the right place (normally I think this is the same place they started from, but there might be exceptions?), if they don't then you have to get them there - either as a passenger on another train or in a taxi. Overtime is also not free (although this wont, I think, be the controller's primary consideration it will be on the list) so if you have a driver due to finish in 90 minutes at Ealing Common who is currently at Earl's Court it's not the best idea to put them on a train going to Upminster. You could just put the train as a Tower Hill and back, but if the bay platform at Tower Hill will be occupied when it gets there you'll be delaying anything behind it, and the unit might need to end the day at Upminster.
There are probably more things that I've not thought of that need juggling too.
unit needs to be at

The press really hate these "jobsworths" who insist on obeying the law.

But they wouldn't let the railway off if a driver has an accident, either driving a train or driving his car home, if he had been made to work in excess of his legal hours.

A tube driver's hours run from the time they book on until the time they book off, the latter can (usually?) only be done at the scheduled place. There is also a legal requirement for a certain time between shifts so if a driver books off say 2 hours late, that could mean they cannot book on the next day until 2 hours after they were scheduled to. If you have enough spare drivers to cover all the affected drivers, and nobody else is sick or on a training day or the like then it's not too much of a problem. However if you don't have enough spare drivers (and the margins are getting tighter, based on aslefshrugged's posts) then you have cancellations and delays on the next shift too. Obviously if things are already delayed then recovering from an incident is going to be harder.

The point is that it is actually in everybody's long-term interest in most cases for drivers and trains to end up where they are meant to. There are times when it is required to taxi drivers around late but remember the overtime and taxi fare costs have to be paid for out of your fares, and that is money that cannot then be spent on maintenance, upgrades, etc.