The tunnels on the Godzilla rail line are notoriously dark and moist. Riding a rail car through them is not recommended unless it is equipped with acid- and radiation-proof plating. 83

https://www.youtube.com/watch?v=QKpzU2GSVC0

A cute Godzilla/Fiat commercial inspired this, though of course I said "There's no way he would choke on a Fiat. Why, I bet he could swallow a train car...." In fact, I drew Godzilla too small in this, if the commercial is accurate.