Same two characters as 倒车, to change buses, but that word takes a third tone. Backing a vehicle up is the fourth tone, 倒车, with the same 倒 as in 倒退, to move backwards.
usage
Standard in anything to do with driving: 倒车影像 is a reversing camera, 倒车雷达 a parking sensor, and 倒车入库 the reverse parking item on the driving test.
