More importantly, there should be a cut-off switch to stop power to the train, so it doesn't gather speed leaving the platform dragging something, or someone, along with it.
It should be very simple. Our Volvo won't lock if a door is not closed properly, so cutting off the controls to start a train should be equally simple.
Train doors do detect objects trapped. But the more sensitive this is, the greater the chance of delay as passengers try to board when doors are closing. Trains give visual and audible warnings that doors are closing.
The majority of accidents similar to that described are caused by passengers ignoring warnings and deliberately forcing doors open.
errr, no there isn't. at present it relies on the vigilance of the driver or the guard to spot if there's any issue with starting the train. at this time, if you were to put your hand in a closing train door, it will trap you.
Well there always used to be in the days when I regularly used the trains, so presumably it has been discontinued in the cause of profits before people.
very few trains in service today have this facility, the most notable being on the Victoria Line, where (as you say) constant delays resulted in the sensitivity being turned down.