There have been solar car competitions that colleges have been doing for decades. Here's a YouTube compilation of one that ran last week: https://www.youtube.com/watch?v=ZBin-oXBJzM

I think it can help calibrate people's intuitions about what you can expect out a pure-solar car.

You also need to remember that inside those shells is basically nothing but a driver. No AC, no seats for people beyond the bare minimum. And that's broad daylight. So you need to look at them doing 20-30mph and bear in mind that it's still not comparable to a street-legal sedan of a similar size doing 20-30mph... those cars are essentially as close to "a mobile cardboard box" as the competitors can make them.

You might be able to build something that people would agree is "a bus" that moves with a couple of people on board, but it probably will stop moving once it enters shadow. Anything that we'd call "a bus" is going to need a lot more physical material per unit solar input than those cars have. I'm not sure that even "moves with a couple of people on board" will necessarily end up being faster than those couple of people walking, either. It's effectively impossible to power a vehicle with its own solar footprint in real time. It also ends up difficult to use them to power batteries because having to move the additional mass of the batteries eats up the advantages of being able to gather power for larger periods of time. It's possible, because of course you can hook a car up to solar panels and eventually charge it, but you don't get very many miles-per-day out of it for what fits on the car itself alone if you work the math.