I have ridden old cruisers with just a rear coaster for a few years now. I road them when I was kid too. They are safe but the reason they work is that they don't go fast. My bike pedals to speed quick which is topping out a little over 12 mph. So my momentum is not that high, so when I lock up the rear brake there is not as much tendency for it to lift off the road. Still if I could find a hand brake that could be added to it I probably would. Generations road these things.