I just thought I'd chime in with an agreement about width, light spacing helping with speed & distance perception. Back in the late 1990s when GM started making daytime running lights (DRL) a mandatory feature on all of their cars, they came out with a few, like the Saturn, which had those lights set inward very closely. I thought that was an awful design and that they should've positioned those lights more out to the corners. And sure enough, I later personally witnessed at least two near-collisions involving those exact same cars coming out of a tunnel or out from the shadows of an overpass when someone pulling into traffic seemingly had misjudged how close those cars actually were. Having those DRLs close together creates the illusion that the car is further away than it actually is. I spent some time Googling to see if I could find anything in the way of accident reports or studies on the topic but didn't come across anything. Currently, I position two Cygolites (a Dash 460 and a Dash 600) as far apart on my handlebars as much as possible just for visibility, with a 3rd light dedicated for illuminating my path. Similar thing with my trike, I put two blinking rear lights out to the sides just to emphasize that this is something wider than a bicycle to pass. I plan on fabricating and mounting a length of pipe behind the seat my Cruzbike for the same purpose. It's also a great redundancy over having just one light in the front or back in case the battery dies, or something. Front & back, having two or more widely-spaced lights can aid the perception of your speed and heading for others in traffic around you.