You have to calculate the energy loss of a car each XXX meters. Imagine there are inductive couplers each XXX meters apart. Now, it could be the energy you need to transfer into the car every XXX meters is not such big..
Btw, "to demonstrate capability" does not necessarily mean the stuff would work under real conditions.. (even I think this is how all cars will work in 100 years from now..)
PS: say 50kWh battery in a small car, and it can do 200km with it (all an average). The loss is 50kWh/200km=0.25Wh per meter. You have to feed say 25Wh every 100m into the car battery then..
Edit: added "h"