Driverless, computer-controlled trains at Dallas-Fort Worth International Airport (DFW) have windshield wipers. But the train doesn’t need to—in fact can’t—see the physical path in front of it, and the train’s human passengers don’t need a clear view either. Do we think that, if we can’t see, the train won’t be able to either?

Another possibility: The trains are off-the-rack and came with wipers already. I wonder if the wipers activate when it rains. If so, how? There would have to be moisture sensors, because there would be no human to turn them on or off.