I am building a route that is shaped somewhat like a spoked wheel. There is a large metropolitan area with three spokes radiating out from there. The area in which i would like some advise is establishing mile markers and as a by product, how many miles of track are laid. What is the best way with type of configuration.
In regards to "establishing mile markers", it would depend on the intent of each of the "spokes".
If they are one Railroad, with "routes" radiating from the Metro-center, I would make the metro-center mile zero, with each radiating leg having it's own set of escalating mile-markers.
If each radiating leg is a different Railroad, each joining at the metro-center, and sharing a Terminal, then you could go either direction (towards or away from the Terminal), and the mileage could be either zero-radiating out, OR a fictional number then increasing as you enter the Metro-center, each terminating with a unique mile-number.
While I agree with Jcitron's suggestion of constructing a "one mile" consist, to reuse in measuring and placing mile markers (accurate around curves), I personally use the longest cars I can find, then put a shorter one on each end to get the correct length. For example, instead of (100) 52'8" cars to get 5280 feet, I use something like (58) 86 foot box cars (actually 89 feet long over couplers), plus two 54 foot hoppers to get my 5280 feet.
6 of one, half-dozen of the other. (sixes)