Interesting Shadows

On one of our after dinner walk here in town we have noticed very interesting shadows on the bridge decking. This bridge is century old railroad trestle that was converted to walking trail bridge with street lights and chain-link fence on both sides. Last year it was renovated and street lights that lined one side of bridge were removed and replaced with large street lights at each end with additional rectangular spotlights. They each burn at different temperature and consequently cast different color shadows, one is orange and the other is blue. Where the shadows overlap the color changes to usual dark grey, almost black shadow. These shadows only appear very close to subject that casts the shadow, in this case chain-link fence and fence posts. Now I have to find out what sort of physics are in play here, it will be fun.

The lights in daylight...

...and at night.

Notice how quickly the shadows lose definition...

...and how the intersecting shadows turn black.

Photos at night: Canon Rebel T1i, EF 36mm at f/11, 05 sec., 1600 ISO, Cullmann tripod, Cullmann ballhead.