This small program visualizes .gpx files (in this case for railway routes). Tracks from multiple files can be animated simultaneously or sequentially. The sequential animation order can be changed after file upload using drag and drop.
The BRouter website is a good place to start for creating GPX tracks.
Try it yourself here: gpx-visualizer.
The animation is based on the leaflet plugin SnakeAnim by Iván Sánchez Ortega.
demo.mp4
Map Data Copyright OpenStreetMap