G” Scale equivalents: Railroad curves are actually a bit complex - not just a simple radius. They are measured in degrees of curvature per 100 ft. To simplify this, a very sharp curve for a 3 ft. narrow gauge railroad is 30 degrees. The equivalent curve in a “G” Scale layout is about a 7 ft. radius. Most modern railroads like to keep the curves to less than 2 degrees. To reduce the high degree of wear, many curves have automatic grease units built into the rail to help reduce friction.