BART in the SF Bay Area runs on dedicated tracks and had MANY teething problems with its computer control system. The system had a problem sensing where trains actually were. The solution included putting scrapers on the wheels to remove rust to improve the electrical positioning signals. This made a system that was supposed to be whisper quiet not so quiet, but I suppose it was a worthwhile price to pay for safety. Other problems included doors failing to open, and once open, failing to close. There have been mishaps with the trains, including fires, and people committing suicide in the stations in front of arriving trains. But as far as I know no BART train has ever collided with another.
Currently BART is saying the entire fleet of cars is in dire need of replacement, and they are looking at a huge project to replace all of them. Money of course is a major issue, with fares constantly going up but the system still needing massive infusions of tax funds.
I hope that if they do get new cars, they will decide to get interiors that can easily be hosed down. The current cars have fabric upholstery and carpeting, which can never be adequately cleaned and the stench on some of the cars is unbearable. I understand from friends who work on the maintenance side of the system that all sorts of disgusting things are left in the cars - including human excrement. Since some people insist on behaving like animals, the cars need to designed as if they are transporting animals.