I was looking for a bridge for my children's large building block train from Denmark. I found one on Thingiverse and teamwittholz. I modified the model slightly so that the bricks fit better for me https://www.thingiverse.com/thing:5844164

There are 3 different bricks that are labeled. They must be used in the correct order: 1 - 2 - 3 - 3 - 2 - 1 - 1 - 2 - 3 - 3 - 2 - 1. The project includes all bricks for a complete bridge.