Layout Designer Doug Gurin provides some considerations when planning a layout in this video, specifically designing curves. It is important to consider curve radii when setting up a model railroad layout. Prototype railroads use much broader curves than model railroads, but model railroad equipment is able to negotiate sharper curves.
When selecting an appropriate curve radii for a compact layout, pick different radii for different situations instead of a single radius throughout the layout. Use a broad radii where mainline curves are visible outside of their arch and use tighter curves when they are visible from the inside. These are situations such as hidden curves or curves with short locomotives and cars.
24 inch curves are recommended for mainline hidden track and staging while 18 inches is recommended for hidden branchline track. Sharp visible convex curves can be disguised to look broader on the layout by raising mainline curves higher than any neighboring ones. Gurin recommends raising the outer rail a gradual six scale inches to make the curve appear more prototypical and large. Use smooth flowing transitions when connecting straight track and sharp curves and block any unflattering sharp curves with visual distractions.
Foreground detail such as structures, trees, highway overpassesor, and industries are such destractions. Move curves away from the edge of the layout to create room for these visual elements. Using at least one broad visible curve can be great for a layout and can distract from the sharper curves. If the curve is seen from the outside it will seem larger than if seen from the outside. For more videos on layout planning and tips to track building, visit the Model Railroad Academy website.