This is partial text from the full article (usually with photos) at https://modelgeek.com/news/hard-foam-bridges-and-archeology-sites-railroad-modeling
I bet you could split those down the middle and fill it with scrap foam to make a wider bridge / more appropriate for a larger scale…
DIY! The material is also known as XPS or Styrodur. The tabletop modelers use it a lot to make buildings/terrains.
German but the video alone shows it