Let's suppose you have an economy where you're the only person in it. You grow your own food, fetch your own water, cut your own hair, build your own house, and all the other activites that life involves.

Now imagine you suddenly discover a neighbour. Great, you now decide to grow the food, cut the hair, while he can fetch the water and build houses.

Suddenly another person comes, and as more and more people come into your world, you all become a little more specialised and more efficient at your tasks.

Overall, providing transaction costs are sufficiently low, this increased specialisation will probably lead to greater productivity and efficiency.

So, this all sounds well and good, but what does it have to do with cars? Well, cars (and other forms of transport) make the world a smaller place by making travel easier. The number of "specialists" you can reach vastly increases with a car, and thus it allows for greater specialisations and greater efficiencies.

The internet does the same thing to some extent, by the way.

In other words, cars have a very real effect on the efficiency and productivity of the world we live in, and getting rid of all cars would hinder this.

Guns, on the other hand, do not have this direct impact on efficiency.

Having said that, you are right, taking away cars would probably decrease deaths (via the road toll). Is it worth it?

You could calculate it. All you'd need to do is compare the dollars saved in car crashes and medical plus the dollar value of the lives lost (which is what you'd gain if you banned cars) to the dollar value of the efficiency loss you'd incur by getting rid of this.

You'd probably also want to include a value for the "freedom" people enjoy from owning a car (as you would with a similar "gun" analysis).

Just my 2 cents,

- Thomas. :)