boneh3ad said:
Anyway, I doubt many studies have been done because the results from one shape such as spheres doesn't really have any bearing on other shapes due to all the factors involved. That sort of research wouldn't really help anyone with their driving strategies.
I agree with your reasoning as well. I also had thought of the lack of implications/continuity for an experiment focusing just on spheres, since if we look at more complex objects, the relationship that was determined would mean nothing; I previously believed that it might become a worthwhile stepping stone for future experiments with more variables such as shape and fluid characteristics.
Now that I think of it, research on slipstreaming/drafting may interest scientists since it may have important ramifications in human life other than racing. For example, the price of jet fuel has skyrocketed in the past years and its availabilty is dwindling. An interesting technique researchers are thinking of implementing for fuel economy is changing the design of passenger planes completely in order to fly slower (the physics behind this move is very interesting and I think I will create a thread on it). Also, another concept is having passenger planes follow one other in maybe groups of three to reduce the work needed to achieve lift, and thus reduce fuel consumption; this would be achieved by the two trailing planes flying in the wing-tip vortex of the leading one (just like the V formation many birds use to save energy on long-distance flights).
I know that lift and drag are two separate forces, but planes could use the low pressure area created at the back of another plane in order to reduce drag and fuel consumption even further.
By researching in greater depth the phenomenon of slipstreaming/drafting and its implications for aircraft, physicists could do their part in reducing the greenhouse effect.
In my opinion, even though there are many factors determining the effectiveness of slipstreaming, scientists will eventually find general and even specific relationships between most variables. Since we are in the realm of fluid dynamics, just look at naval architecture: when determining the hull form for a given ship that will travel the fastest while remaining fuel efficient and stable, the quantity of variables that have to be taken into account is astounding (density, viscosity, and flow of water; length, depth, freeboard, draught, and beam of ship; frictional, residuary, and wave-making resistance; drag, lift, and thrust coefficients; wetted surface area, block coeffecient, waterplane area, and Reynold's number; just to name a few

) Even with so many factors to keep in mind, naval architects manage to design fast, efficient, and stable hull forms no matter the needs of the client.
There will be a lot of trial and error as well as very complicated concepts to quantify, but the physics of slipstreaming could become a far-reaching discipline!