Atlas Track Planning is described as 'Atlas is proud to offer free, downloadable track planning software for your use in creating magnificent layouts in HO, N & O scales using Atlas track'. There are nine alternatives to Atlas Track Planning for Windows, Mac, Linux, Chrome OS and BSD. The best alternative is TRAX, which is free. Other great apps like Atlas Track Planning are SCARM (Freemium), TrainCad (Free), Empire Express (Paid) and RailModeller (Freemium).
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.