These observations lead us to six principles of vehicle design and vehi-
cle use for more-efficient surface transport: a) reduce the frontal area per
person; b) reduce the vehicle’s weight per person; c) when travelling, go at
a steady speed and avoid using brakes; d) travel more slowly; e) travel less;
and f) make the energy chain more efficient. We’ll now discuss a variety
of ways to apply these principles.
A widely quoted statistic says something along the lines of “only 1 percent
of the energy used by a car goes into moving the driver” – the implication
being that, surely, by being a bit smarter, we could make cars 100 times
more efficient? The answer is yes, almost, but only by applying the princi-
ples of vehicle design and vehicle use, listed above, to extreme degrees.
One illustration of extreme vehicle design is an eco-car, which has small
frontal area and low weight, and – if any records are to be broken – is
carefully driven at a low and steady speed. The Team Crocodile eco-car
(figure 20.2) does 2184 miles per gallon (1.3 kWh per 100 km) at a speed
of 15 mph (24 km/h). Weighing 50 kg and shorter in height than a traffic
cone, it comfortably accommodates one teenage driver.
Hmm. I think that the driver of the urban tractor in figure 20.1 might
detect a change in “look, feel and performance” if we switched them to the
eco-car and instructed them to keep their speed below 15 miles per hour.
So, the idea that cars could easily be 100 times more energy efficient is a
myth. We’ll come back to the challenge of making energy-efficient cars in
a moment. But first, let’s see some other ways of satisfying the principles
of more-efficient surface transport.
Figure 20.3 shows a multi-passenger vehicle that is at least 25 times
more energy-efficient than a standard petrol car: a bicycle. The bicycle’s
performance (in terms of energy per distance) is about the same as the eco-
car’s. Its speed is the same, its mass is lower than the eco-car’s (because
the human replaces the fuel tank and engine), and its effective frontal area
is higher, because the cyclist is not so well streamlined as the eco-car.
Figure 20.4 shows another possible replacement for the petrol car: a
train, with an energy-cost, if full, of 1.6 kWh per 100 passenger-km. In
contrast to the eco-car and the bicycle, trains manage to achieve outstanding
efficiency without travelling slowly, and without having a low weight
per person. Trains make up for their high speed and heavy frame by exploiting
the principle of small frontal area per person. Whereas a cyclist