I have long wondered why personal cars are being tackled. Surely that's the hardest problem to solve. Easier to automate would be trains, large container ships

I have long wondered why personal cars are being tackled. Surely that's the hardest problem to solve. Easier to automate would be trains, large container ships, tube trains, planes or buses (fixed route, designated stopping zones). Granted planes and ships travel in more dangerous regions, but I think they should be flown 99% of the time by computer and pilots only taking over in an emergency.