Children and car safety

I used to drag the carseats with me when we were traveling, and pay for the extra time to install them in taxis. I feel safer on a city bus, since they tend to fare better than other vehicles in an accident. I would usually try to find a seat that faced sideways or backwards, so I could put my child's back to where the point of impact would be, if we were thrown forward. If we have to sit facing a metal bar. I usually put a back-pack or jacket in-between my children and the bar.

If I take my children in a taxi, my baby can usually stay in his buggy and he can also do that on some buses. But if that's not possible, I have to just have him on my knee. I understand the importance of having a carseat but I can't see why it's any safer to have your child on your knee on a bus than it is in a car.