For many years we’ve had intermittent discussions about ballast color relating to differences in mainline, passing siding, and spurs. One conclusion I think we have verified is that railroads obtained ballast through the most economic means. If it was cheap and close, they bought it. Hence, you might see patches of different color ballast in areas that were maintained when an alternate source was more economical. Another supposition that seems to be pretty well supported was that coke was used a lot on spurs and yards. Coke was cheap and readily available especially to the coal haulers. But coke is soft and crumbles easily. So, railroads wanted a better ballast on the mainline than coke – something that would hold up to higher speed and heavier traffic. But sidings and yards would often get the coke ballast. The coke would break down quickly creating a dark “soil” like look. As it broke down, drainage would degrade causing the puddles sometimes seen between tracks in a yard. (Puddles are a bad sign that the drainage is failing – so not too much of this.)

But the one element never explained or supported is that a lot of modelers use a different color ballast between mainline and passing sidings. On “real” railroads, passing sidings would generally receive the same ballast as the mainline, so why should they consistently be a bit darker than the mainline? Finally! – I found an explanation. Mainlines would receive maintenance regularly. Fresh ballast was dropped and swept in place anywhere the tracks raised or ballast fell off. Then as the ballast broke down (potentially causing drainage issues), the tracks would be raised and the ballast removed and cleaned or replaced. So, mainlines always had a relatively fresh ballast look. Passing sidings, while the ballast was high quality – the same as the mainline ballast, would receive maintenance much more irregularly. Passing sidings needed to hold the weight, but not usually at mainline speeds. So, the ballast broke down at a slower rate, and maintenance on the passing siding was lower priority than the mainline ballast maintenance. Hence, passing siding ballast went much longer between maintenance. In turn, the ballast would typically show a greater amount of dirt changing the color slightly. Areas with light colored limestone ballast would get slightly darker or browner (dry soil color) because of the constant dust worked up by train movement. Additionally, oil and ore fall-off would collect in spots on the ballast. Areas that used a red or colored rock ballast would often change to a grayer/dirtier look.

So, when we ballast our new layout, mainline ballast should vary but look relatively fresh. Passing sidings should generally get the same ballast but with weathering applied to show less maintenance. Spurs and yards can receive a variety of ballast colors, but often coke colored with a lot of weathering spills and can show a breakdown of the ballast.