In a previous post, I discussed that Platooning would be used for several reasons. In addition to the traffic control reasons, a significant reason is the fuel savings that results from drafting. Drafting is the close following of one car by another car. Or, as wiki states, it is “a technique where two vehicles or other moving objects are caused to align in a close group reducing the overall effect of drag due to exploiting the lead object’s slipstream.” The following car is said to be “drafting” if it is so close as to be able to utilize the airflow from the leading car to get a little extra “pull.”
Briefly, drafting does two things. First, it permits the following car to be more fuel efficient. Secondly, it permits the second car to use “extra” power” to push the first car forward. The Wiki article on drafting explains in some detail the science, how they interplay with each other, and their current uses in racing.
When a car is traveling fairly quickly (the effect is minimal at speeds below highway speeds) a substantial portion of the energy expended is used not just to move the vehicle along the ground (rolling friction) but also to cut through the air. If another vehicle (it could be a car, truck, bus, or hyperspeed trolley) is cutting through the air, a following car could follow close enough to get an energy savings. This is because the leading vehicle leaves a vacuum (fewer air molecules) behind it. The trailing car can push the less dense air more easily. In fact, Mythbusters did some “research” into this. Currently, the closeness required for drafting to provide a substantial energy savings is unsafe. The closeness will, in the future, likely be determined by the limits programmed into the computer to both stay safe and get optimal drafting. What actually ends up happening is that the trailing vehicle actually runs the engine in lower RPM (“Slower”) and is still able to maintain the same speed as the leading vehicle.
“Bump Drafting” is the name given to a racing technique in which the following car actually pushes the leading car. This is necessary on some race tracks as the maximum engine power is limited. Since the power is limited, a car that isn’t drafting may actually be going as fast as it’s engine will push it. If a team mate approaches from behind, he may be able to draft, and therefore run his engine in a lower RPM, using less fuel. Alternatively, if he decides to run “all out” he will bump the lead car, pushing it faster.
I expect most readers will understand the advantage of drafting from an energy saving perspective. Energy Savings is synonymous with fuel savings is synonymous with saving money. What about using this bump drafting? Using a racing technology for road vehicles is not unheard of, but will people really want to bump into each other?
I suspect several aspects of vehicular autonomy will converge to make the answer “yes.” First, with automation and springs, cars “connecting” can be unfelt by the driver – at least compared to Pennsylvania potholes. second, with automation, trailing vehicles can “see” everything the lead vehicles can see. Therefore, if a road condition triggers breaking, other cars will stop as if they saw it. Furthermore, the cars will all be in communication. Because of that, the trailing cars will all stop once the first “says so.” Once drafting and platooning are accepted, the size that engines need to be to go 100+ MPH will be much lower.
I really look forward to exploring the interplay between vehicle design due to safety (lighter, faster), that due to comfort (heavier, faster) and that due to energy efficiency (lighter, slower, nimbler.)