Streetfilms: Tap Foot, Lights Blink, Cross Street

Along Seattle's historic waterfront I happened upon a unique
pedestrian-activated crosswalk that blinks as people cross. Yes, I have
seen over a dozen lighted ped signals before in myriad cities, but all
required the user to press a button to manually begin the cycle. So, you
ask, how is this one different?

Well check this out: As you enter the crosswalk, make sure to step on
the yellow rectangle on the sidewalk. This activates the lights that
line the crosswalk. Drivers stop and it should be safe to begin your
adventure. You'll feel a bit like an airplane coming in for a landing.
Frankly, it's very empowering and a lot of fun!

Reason dictates that A) there must be a sensor contained within the
yellow pad, or B) there's a helpful gremlin who lives underneath and
throws a switch for pedestrians. Regardless, anyone else seen one like
it?