"The Mainstream Class has minimum design requirements based on the characteristics and combined city and highway driving profile typical of today's popular, mixed-use vehicles."
They are actually encouraging the best combination of speed and economy. The mileage standard for the Qualifying race is 75 MPG. The mileage standard for the Final Race is 100 MPG. I doubt the ultimate winner can do both (100 MPH and 100 MPG) at the same time.
The reason why it is a speed measured race is pure economy races are a little too esoteric to be interesting (read: boring), and the winner will be easily determined. There will be various strategies at work by the different teams that should keep the interest level up.
Don't forget the target is a vehicle for the general population to buy. The hairshirt mentality often on display here doesn't play in Peoria. The X-Prize people believe we can have it all: comfort, speed and economy. As I've often said here; 10-15 years from now Americans will be driving 400hp electric Hummers that go 200 miles on a charge. This contest will bring that day sooner rather than later.
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