Infantry can be crushed by some vehicles sometimes automatically or at user discretion using force-move. When a vehicle drives onto a cell where one or more infantry are residing then there is a chance that they'll get crushed. The chance of surviving a crush attempt is 75% for regular infantry and 95% for a hijacker.
Infantry have a higher chance (how much?) to be crushed when standing in a road.
Vehicles that can crush infantry can also crush barbed wires and sandbags. Mammoth tanks can crush concrete walls too.