The Daring Dufas wrote:
Pete C. wrote:
The Daring Dufas wrote:
HeyBub wrote:
When used in traffic signals, the lights don't get warm enough to melt snow.
The snow obscures the signal and people die.
"Cities around the country that have installed energy-efficient traffic
lights are discovering a hazardous downside: The bulbs don't burn hot enough
to melt snow and can become crusted over in a storm - a problem blamed for
dozens of accidents and at least one death."
http://news.yahoo.com/s/ap/20091216/...red_stoplights
Some cities are considering hiring midgets to sit atop the signals with
hair-dryers and long extension cords to keep the traffic signals clear.
(Some species of monkeys could be trained to do the job, but the training
time would take too long to be effective this season.)
I can see a couple of ways to prevent the problem and one is to use
the type of heater that is used in outdoor CCTV cameras. Another
way would be a simple snap on clear plastic cover that would prevent
snow from getting into the hooded area. Oh yea, teeny little windshield
wipers.
TDD
I would expect it wouldn't be that difficult to install an optical
sensor at the end of the hood looking back at the light and use that to
switch on a heater if it did not detect sufficient brightness when the
signal light was on. No extra energy use unless there actually was snow
obscuring the signal. Probably around $20 manufacturing cost, so sell
for $200, a fairly insignificant cost given what the signals themselves
cost. Also only needed in climates that have blowing sticking snow.
Using the same material as used in the manufacture of self regulating
heat tape, an inexpensive add on heater that worked automatically could
be produced.
TDD
No point in heating all the time, or even just when it's cold. Much
better to heat only when it's cold and something (snow) is obscuring the
light. The minimal cost of the extra control components will be far
outweighed by the lifetime power savings of only having the heater
active during sticking snow events.