Even without the awful sales figures of GM, Ford, and the other horseless carriage companies, mathematically cars are dead.
Car sharing is growing by leaps and bounds. The math: owning a car costs $8,500 a year (gas at $2-$3/gal., insurance, depreciation, repairs, tires). Car sharing costs $8 an hour (including gas and insurance). So you can drive for 1,000 hours (essentially 20 hours or half time every week).
Gen Y is clearly switching to car sharing. There's no evidence Gen Y will be buying cars.
Now look at this math. Some 17 people can share one car. They say each car in car sharing takes another 17 off the road. That means we don't need 16 cars for 17 people, or we don't need 95% of the cars.
Let's be generous and say automobiles will drop to 20% of what they are today. They cannot support roads, garages, gas stations, State Patrol, auto insurance companies, etc. on 20% of the traffic we have today. Mathematically, cars are dead. What does your math indicate?