relay, walk, don't walk street sign

I need some help with a project, I got my hands on a walk don't walk street sign and I'd like to wire it up so the lights for each side flash on and off, but not with each other....ie, one side is lit while the other side is off, and then reverses. Any help with thisd project would be greatly appreciated.

Thanks

I suppose you want a timer to go with it too. What kind of bulbs are in it and what Voltage?