SCARM is described as 'With SCARM you can easily create the layout of your dreams – just download the setup package, install it and start editing your first track plan'. There are more than 10 alternatives to SCARM for Windows, Mac, Linux, Chrome OS and BSD. The best alternative is XTrackCAD, which is both free and Open Source. Other great apps like SCARM are TRAX (Free), TrainCad (Free), RailModeller (Freemium) and Empire Express (Paid).
XTrackCAD is a CAD program for designing model railroad layouts. You can easily create layout of any scale or size. Libraries for many brands of track and turnouts are included. Adding new components is easy with the built-in editor.
TrainCad is a freeware Microsoft Windows program for designing model railroad layouts using standard tracks. Track libraries are available for Märklin metal, C and plastic-tracks in H0, Z and Spur 1, Roco/Trix H0, N track, Atlas N, GarGrave and others.
Cadrail is a powerful CAD program with many different railroad design tools. You can create track plans of any size and shape. There are easy to use drag and drop tools that allow you to snap track sections together end-to-end and align them automatically.