Vehicles of varying sizes and speeds create different pressure wakes behind them, and many people like taking advantage of that wake to save fuel.
Air pressure sensors at various points along the vehicle tied to some sort of instrumentation that informs you when you are completely in the wake ahead of you.
It will also tell you when you are in the dirtiest air, effecting your mileage negatively.
I suspect it should also be speed activated to keep low speed tailgating at a minimum, where little if any advantage is gained from the draft.-- Giblet, Sep 06 2008 pressure sensitive surface pressure_20sensitive_20surface [xaviergisz, Sep 07 2008] maybe you could do this with a external coating on the vehicle that changes colour according to the air pressure (see link for one way of doing this).-- xaviergisz, Sep 07 2008 Just out of curiosity, if you're doing (say) 70mph, how close behind an HGV do you need to be for this to have any benefit?-- MaxwellBuchanan, Sep 07 2008 forget drafting, the automotive industry would die for an inexpensive way of doing wind tunnel testing (this device would have to be even more comprehensive). This is not as simple as a single or multi point pressure reading. Really a MPG reading would be simpler: Use closed loop feedback into a radar regulated cruise control that "finds" the best position .-- WcW, Sep 07 2008 5-8 car lengths behind a tractor trailer?-- Giblet, Sep 08 2008 giblet have you actually drafted before? more like 1 to 1.5 car lengths before there is any benifit. Most rigs produce a ducktail of turbulence at around five carlengths that increases air resistance. However the whole system is dynamic so the shape of both vehicles has to be taken into account.-- WcW, Sep 08 2008 Maybe if you had a caravan or convoy of cars who wanted to draft together (in rainbow order of course), the lead car could use a smoke generator like aerobatic planes use. Then each car will see where there is turbulent flow or laminar flow in relation to the wake of the car in front of them and adjust for maximum draft benefit.-- gomer, Sep 08 2008 So, basically, we're talking about a device to encourage you to stay a couple of car lengths behind another vehicle at high speeds?
I love the smell of natural selection in the morning.-- MaxwellBuchanan, Sep 08 2008 The idea is also to keep you out of the most turbulent area, like the idea posted says.-- Giblet, Sep 09 2008 Respecting the stopping distances recommended by the highway code is already futile on motorways. If you leave the proper gap, someone will fill it.
I did see something on the telly a while back where a train of cars were driving at high speed just a few meters apart. They were using some kind of autopilot that would apply everyone's brakes if the driver in front did.-- Bad Jim, Sep 09 2008 Luckily there is no draft in Canada.-- 2 fries shy of a happy meal, Sep 09 2008 random, halfbakery