Big shadows, why?

[capmotion]

Weird shadows..

The scene is lit by a texture environment. It is an HDR texture of a skate park with concrete in broad daylight.
Anyone has a clue why these huge shadows appear? I have other characters in the scene and they do not produce these elongated shadows.

Thanks for your input
Gabriel

[capmotion]

OK, I've realized the shadows are made by the front and rear bicycle lights, because they are also shining backwards.
Is it possible to make an emission go only one way?

[capmotion]

I've since learned to make my emissive geometry one-sided. Alas, the light shines in the direction of the Normal. I'll leave this solution here if anyone else runs into this newbie error