It’s a British film based on the premise that subway conductors get ten years salary and early retirement if they run over three people. Mackenzie Crook plays a driver searching for his third. It’s a fun trailer – I like how the announcer reads all the cue cards for you. It’s very helpful if you’re blind, or retarded, or a blind retard.
I should also note that in England, they call the subway "the tube". It makes me wonder if they call subway sandwiches "tube sandwiches", which I’m sure your mother would enjoy.