Are there any laws about how long a train can hold up traffic?

The railroad owns the land that the rails sit on plus some on either side.
In most cases, it was there before anybody built a vehicular road that crosses the rails.
The people who build roads for cars and trucks do not own the strip that crosses the rails. So they have to put up with it, or build over or under it.
So no, the vehicular traffic has to suck it up.

I don’t understand why the government doesn’t just take it by eminent domain and grant the railroad an easment.

The laws vary by state, @Judi. I found this.

@Judi If they take the land back they don’t get to collect the tax income from it.

IDK…but there should be. Our hospital is located at the north end of town, almost to the edge of town. There are train tracks that cut the main street at the north end of town, right on the street that the hospital is located on. I’ve seen trains hold up traffic for 30 minutes or more. I always wonder how in the hell the ambulance is going to get through. I know that if they know about it they can head east for a few blocks and go around, “only” losing 5 minutes or so…so, are they notified?

I will tell you the guidelines for putting conduit under the train tracks are so monsterously awful, it just isn’t done.