An interesting thing was posted in the Atari Forums today. Someone has found that you can build railroad crossings by simply building your train track, and then lower the ground where you want your pathway to cross it. Then place your path on this lowered piece. Finally raise the lowered land back to the train track height. You now have a crossing that the peeps will use!
It won't have gates of course, and the peeps will often walk through the train itself, but hey, it's better than nothing.