As the Southern Rail dispute drags on, bringing chaos and disruption to commuters across London and the south-east, the Aslef and RMT unions have attracted widespread ridicule for claiming that drivers should not be required to operate train doors.
Tosh McDonald, the head of drivers' union Aslef, pointed out the safety concerns in an interview with Julia Hartley-Brewer on talkRADIO this week - only for his claims to be mocked. Julia reflected the feelings of many people when she suggested the safety concerns were massively over-blown.
But in fact McDonald and his members have a point. People might suggest the job of opening and closing doors boils down to a single button, but in reality it's far more complicated than that.
Opening and closing the doors actually requires two buttons - safety regulations dictate that there are two, not one, on most trains to ensure drivers don't press a button by accident and open the doors while the train is in the wrong place. What's more, the driver is required to make a judgement call on whether it's safe to open the doors, looking at up to 24 images on a screen the size of an iPad in a very short time.
As soon as the train starts to roll the screens go blank, so the drivers can't even check things are OK as the train pulls out of the station. This makes the driver's job very hard - I've driven many simulators and made massive mistakes on all of them.
You can't speed - go 3mph over and the brakes come on, the mistake is logged and the company sees it. Go through a red light by even a few metres and that's probably your job lost. Fail to keep to time by driving too slowly and you're on a disciplinary warning.
You need to be vigilant 100% of the time - which takes a special sort of person - and having to concentrate through a ststion stop rather than have a minute to rest your brain is going to push them to the limits.
It's also worth bearing in mind it can take a mile or more to bring a train to a stop, so the drivers need to know every metre of the route and where they are on it, so they stop correctly at every station and know when to slow down to maybe cross a weak bridge or negotiate a bit of track that needs improving.
The whole process is very hard to handle successfully. People might talk about a simple process of pressing buttons, but they've probably never driven a train and had to deal with all the manifold concerns - stopping at the right place on the platform, checking everyone is on and off the train safely, checking nobody is trapped in the doors, checking things like coats and bags haven't got stuck.
There have actually been a number of "trap and drag" incidents over the years, some resulting in death or life-changing injuries. Guards play a vital role in avoiding preventing such tragedies.
Guards tell drivers they haven't stopped at the platform correctly and provide support to passengers with mobility issues boarding or leaving the train. They've prevented many accidents by not telling the driver it is OK to depart when they've spotted someone trapped.
They suggest that their eyes are better than the cameras for checking doors are closed properly (and drivers say that not only do cameras fail - causing the train to be cancelled or to miss stops where there aren't platform staff to take over from the cameras) and also there are many occasions where the sun in the wrong place, or at night when the cameras can't actually provide a good view anyway.
Guards don't provide a foolproof failsafe against tragedy. In fact one guard has recently spent time in prison over a passenger falling between the platform and the train and losing her life. But the Aslef and RMT unions feel that that, by transferring all the aforementioned responsibility onto drivers, we will see more mistakes and more staff being prosecuted.
So the unions are doing their job: protecting the guards, who say they already struggle on crowded stations, and drivers. They know that a 12-coach train carrying 1300 passengers will make mistakes, and 'driver-only operated' trains will only compound these errors, sometimes with fatal consequences.
Tony Miles has written extensively about the UK rail industry for a range of publications. You can find out more about him here.