Crash Safety Vs Saving on Gas

Generally smaller, lighter vehicles can achieve better fuel economy than larger ones, all else being equal. The same basic physics means that the smaller vehicles will fare worse in crashes, once again all else being equal. That is not to say that small vehicles cannot be made to do well in crashes. Just that a larger vehicle with the same attention invested into crash safety will do better. Likewise, a larger vehicle can be more fuel efficient than a smaller vehicle if the smaller one has not invested the same level of engineering into fuel efficiency. This video explains some of the tradeoffs between crash safety and saving on gas.

Note that one concern is small vehicles colliding with large ones. That is a safety risk factor that will probably go away in the future, as sustained high and rising gas prices push automakers to elevate fuel economy to priority number one. That will likely result in all vehicles eventually being smaller, thus reducing the danger of a minicar colliding with a large SUV sized car. Even should this happen, there will remain the problem of smaller cars having smaller crumple zones, which leads to occupants experiencing higher accelerations in crashes. That is a basic limitation of physics and cannot be overcome.