I'd like to see how it works with a salted wet road too - do they turn it off?

Apparently they tested just that -

Säll said: “There is no electricity on the surface. There are two tracks, just like an outlet in the wall. Five or six centimetres down is where the electricity is. But if you flood the road with salt water then we have found that the electricity level at the surface is just one volt. You could walk on it barefoot.”

They also mentioned they turn off each segment if there is not a car on it. Each segment is 50 meters.

That's actually reassuring, I'm glad they looked into this.

My follow-up concern is, what if, under these salty and wet conditions, something causes a short circuit between the powered rails?

e.g., either a defective vehicle-side contact where the anode and cathode allow for the water and salt to close a much smaller gap, or if someone deliberately sticks a piece of metal on there.

You'll get a small steam explosion but there are lots of ways for the pressure to escape, and if the circuitry protecting the 50 meter stretch is fast enough that might not even happen.

But will slugs be able to safely cross the road?

No. But in a few generations they'll learn not to. In a few more they'll be expert jumpers.

They said nothing about the wear characteristics of the rail when covered in salty road crap.

Stray current wreaks all sorts of havoc on electric light rail systems. I don't see why this would be different.

It is Sweden. If anyone knows salty road crap it is Scandinavians.

They address that concern in the article. They said the voltage on the surface of the track is only 1 volt when the road is flooded with salty water.

It is used for charging batteries, not providing constant power. It disengages on lane change according to the article, but that should not be a problem if there are batteries.

Sure, but you'll be disconnected for that and you're going to have to reconnect on the far side. That's going to cause some arcing and wear. On the plus side, self driving cars will have something to aim for. Provided there isn't any snow or ice to deal with.

Arcing seems trivially prevented by utilizing two-phase connect and disconnect processes. Don't flow current when changing states.

Arcing from a rail that when filled with salt water gives off 1 volts up at road level?

Water under voltage forms a resistor network (effectively). After some distance it's not that deadly if you don't have potential to neutral.

Arcing may also occur under high current situations with low voltage as long as an arc forms early in the disconnect (just test it on your car battery)

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