This seems to be mostly a US problem, I only really see people from the US worried about this...
As someone from the UK who travels on two trains and a bus both ways (6 journeys total) most weekdays to university, I never had any problems with other passengers, I guess very occasionally there might be a loud baby or something but then you can just put headphones in, and the worst thing that ever happened to my property is my bag got accidentally handed into lost property when I wasn't paying attention because I got on really early and the staff assumed it was left there from the last trip
So you're better off flagrantly breaking traffic laws and possibly getting T-boned than having someone potentially break into your car? That seems like some combination of nonsense and there maybe being some places you should just avoid.
This seems to be mostly a US problem, I only really see people from the US worried about this...
As someone from the UK who travels on two trains and a bus both ways (6 journeys total) most weekdays to university, I never had any problems with other passengers, I guess very occasionally there might be a loud baby or something but then you can just put headphones in, and the worst thing that ever happened to my property is my bag got accidentally handed into lost property when I wasn't paying attention because I got on really early and the staff assumed it was left there from the last trip