Blake,
Thank you for the explanation. I've been aware of the condition ever
since I spun a car at age 14, but not why it happens. There was a light
wind blowing on Sunday with mist in the air.
Another slippery condition is caused by leaves, some thing that nearly
caused a crash in front of me earlier today. A truck approaching an
intersection, moderate speed, turn signals working, applied brakes and
just glided on and on and on toward an increasingly uncomfortable-looking
driver in the stopped car ahead. Finally the locked front wheels started
turning, the tires gripped pavement, and the truck swerved into the
intended turn. No harm done to anything except the nerves of drivers and
onlookers to the event.
Bob
On Mon, 11 Nov 2002 14:31:51 -0600 Bullwinkle <yd3@nvc.net> writes:
> Bob:
>
> <<<snip>>>
> Asphalt paving was slippery wherever I drove. Does anyone
> know why that should be? The earth is not frozen and air temp had not
> been below 32 for several days.
> <<<snip>>>
> Yes, Bernoulli effect. This happens when the temp is close
> to the dew point. Wind blowing across trees and other
> objects causes the vapor pressure to drop just enough that
> the moisture in the air falls out as precipitation. This
> can also cause the moisture to actually come as snow.
>
> Another cause may be a very light almost invisible snow fall
> which can happen when the air temp is above 32.
>
> Very light moisture on the road is quite often slippery due
> to fact that there's not enough water to flush the oil and
> petroleum residue off the road. So you have water on top of
> oil.
>
> We had the same conditions here on Sunday morning going to
> church. Just the pavement was dark damp, but the sidewalks
> were not.
>
> Blake
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