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http://freakonomics.blogs.nytimes.com/2008/03/14/taiwans-solution-to-traffic-jams/

   About a year ago in Taiwan, they started installing countdown
timers at traffic lights at a number of intersections. Some counted
down the amount of time remaining ’till a green light turned yellow
and then red, while others counted down the amount of time remaining
before a red light turned green. Some intersections had both.

   It’s a fact that a certain number of accidents are caused both by
people who jump the gun on the red light, and those who try to make it
through the intersection after the light has already turned red.
Ostensibly, the reason for the timers was to give people more precise
information about exactly how much time they had remaining before the
light changed, in the hope of reducing accidents.

   The results are quite interesting. A research institute within
Taiwan’s Ministry of Transportation released a report showing that at
187 intersections which had the timers installed, those that counted
down the remaining time on green lights saw a doubling in the number
of reported accidents, with a 33 percent increase in the number of
injuries, while those that counted down until a red light turned green
saw a halving in both the number of reported accidents and injuries.
Intersection that had both red and green light timers saw a 19 percent
increase in reported accidents and a 23 percent increase in injuries.