power is power is power.

Lets say in 50 years we have an ...."engine"..... that is 98% efficient. 98% of the "fuel" goes into transportion.

Transporting 1 person at a time will always be inefficient.
Transporting 1 ( or 2 or 4 ) person with a 200 Horsepower power plant will always be inefficient.

This is not a knock down of the "hydraulic hybrid", this is just an editorial.

We NEED low powered personal transportation... whether that is electric, ethanol, hydrogen, gasoline, or plutonium powered... does not really matter.

I just bought a 4 passenger vehicle for $5000 that goes 0 to 40 miles per hour in 15 seconds on the flat and level... and will go up to 50 or 55 MPH eventually. This car weighs 900 pounds and has a five (5) horsepower, 1 cylinder, gasoline engine. It has a CVT (belt drive). It does NOT have a CD player or air bags or automatic anything. It was built in 1941.
(from a pre-WWII design) Does it meet SULEV standards? Heck no. But it comes with a 3 gallon gas tank, good for 150 miles or more.

In the "old" days... you generally had 1 horsepower per person. *( you rode the horse )
A stagecoach with 4 to 6 people inside might have 4 to 6 horses out in front. This worked well, but was rather slow.

Today we have a ratio of 200 HP per person, sometimes more than that. But we are not going 200 times faster. 200 times the power gets us to go about 8 times faster.

My 1941 motorcar if I put 4 people in it, is close to a 1:1 ratio again... yet it will go 5 times faster than a live horse would.

I say I have a vehicle... better than the horse!!!
This just demos how little power we actually need.
At 5 HP and under, Solar Cars become viable.
-John