If you read the "Railroad safety and appliance Act" of 1893,amended '95,'98,'03. And etc. It spells out that the running boards are NOT to be painted, and if painted or coated, they must have the same traction as unpainted wood!
That doesn't mean that they never got sprayed when re-coating the roofs, it just means that they weren't suspost to get painted. There was NO specifications attached, as to the supports. The Act spelled out the size of the boards total width, but not the size of the boards, but their must be 1" gap between the boards. Also spelled out is the minimum overhang past the end of the roof, and the required attachment hardware size and position.
Dave