In Gibraltar, the main arterial road out of the territory intersects the runway of the international airport. Every time a plane lands or takes off, the road has to be closed.
This setup sounds like exceptionally bad civic planning, but Gibraltar is so narrow that they didn’t really have a choice. Much of the territory is dominated by the famous Rock of Gibraltar, which is a bit too lumpy and rock-shaped for runways.
The road, Winston Churchill Avenue, is the territory’s main connection to Spain. Whenever a plane is scheduled to land or take off they just close that road long enough for the plane to drive across the road.
They’re planning to build a tunnel underneath the runway, but as far as I can tell it’s not done yet. You can see a plane crossing the road in the video below (at around the 5:00 mark).
One final note: Gisborne Airport in New Zealand, Manakara Airport in Madagascar, and Bacha Khan International Airport in Pakistan all have railway lines that cross their runways. This seems like a bad idea.
[Thanks to Shaun T. for suggesting this topic.]