How long was the red light, if you had no clock with a second hand but could work it out later at home?

real-life/timing.traffic.light New

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Problem

How long was the red light, if you had no clock with a second hand but
could work it out later at home?

The other day I was driving home.  I always seem to miss a left turn
light and have to wait for it to turn green again.  It seems to take
forever.  I thought it would be nice to know just how long the light is
red before it turns green again.  Unfortunately I didn't have a clock
with a second hand handy.  I was however able to figure out how long the
light was red within about a second, but not until I got home.  Any
ideas as to what I did?

Show solution

I counted the clicks made by my turn signal, and when I got home I used
a clock with a second hand to determine how long it took to click the
same number of times.  Other things I could have done was to time my
windshield wipers (assuming it was raining) and to time how long between
certain points in a song on the radio (assuming I was listening to the
radio, only one song played while I waited, and the song was not overly
repetitive).

-- Chris Cole, rec-puzzles.org wiki