The Traffic Accident Reconstruction Origin -ARnews-

Re: Truck Slipstream Effects

Rod Macdonald (frmrmtr@aol.com)
Wed, 5 Aug 1998 23:29:42 -0400 (EDT)

Although I'd certainly bow to the results of controlled scientific testing, in my practical riding experience (27 years or so...) I've never experienced a "sucking" effect either - though I have done the 'push' and the 'dead spot' and the 'draft'...the speeds don't seem high enough or far apart enough to impress me as effecting even a small bike so severely.

conversely I have heard this effect discussed in relation to high speed trains and pedestrians - but that's high speed trains and pedestrians...

are there independent witness statements to cooborate the described movements of the vehicles, or only the location of damage?

some thoughts/possibilities:

a wandering trailer - though you didn't specify that the truck was a semi, something I have seen all too often - though again it seems at higher speeds.

an unsafe turn or lane change by either party - could the rider, perhaps initiating his movement at the same moment he checked his blind spot, have moved laterally into the truck during perception/reaction as the truck, moving at 20 to 30 feet per second faster than the rider, overtook him? A witness could perceive this action as the rider turning to look at the truck as it "sucked" him towards it. Or the rider making a lane change without signaling or checking could be perceived as being "sucked" in unawares.

also- perhaps most likey, rather than an over-response, an improper response - motorcycles turn by 'countersteering' - that is - to go left, push on the left handlebar...the rider, startled by sudden passing of a large truck at a higher speed, attempts to turn away from the perceived danger, and in so doing countersteers into it - very common in inexperienced riders who don't understand the principle. Invariably, when the initial steering input produces the wrong result, the inexperienced rider compounds the error by adding more improper input- and eventually vectors right on into the target. And now might you also have a situation a witness might perceive as the rider, aware of the truck, trying valiently and vainly to steer away from the truck as he was sucked under?

forgive me, I digress with melodrama - check with your local Motorcycle Safety Foundation Riding School for more about countersteer, and take a good look at your rider's experience level - the smaller bike size does tend to hint at a neophyte...
Rod Macdonald
frmrmtr@aol.com

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