Gene,
Technically they will work the same no matter how you space them. However, there could be some ramifications down the road. By alternating or staggering their placement theoretically when you get around to creating blocks you could have one of the feeds for a certain block located in the adjoining block. I do not see what you would gain by staggering them. If nothing else, think of the underneath side of the layout. If you keep them adjacent to each other, both wires will be hanging down in the same spot and easy to locate and trace in case of electrical trouble down the road. When you have two wires hanging down next to each other you can pretty well figure they are track feeds. When you have only one hanging down underneath the layout it is anybodys guess if it is a track feed, lighting, block control etc. They all tend to look similar from the underneath side. And like I said, what would you gain?
I should know the proper spacing distance but I can't think of it. This probably isn't proper to the rivet counters but I usually just put the cork roadbed next to each other which gives me the necessary room and keeps them pretty much straight. You do have to watch this in curves as you need a little extra separation to allow for overhang. I'm sure someone here can give you the "official" recommended spacing.
Don't forget you can use a longer bridge to span a shorter distance which gives you room to slope the terrain down at a gentler angle.
The rest of the boys (and girls, sorry Dot) will be waking up and joining later so I'm sure you will be hearing lots of different theories on this.
Mike
