Comment by Aaargh20318

> Supermarkets that have a step-less escalator (e.g. to go to the parking lot in the basement) also use these locking wheels to make sure the cart never moves on the escalator.

we have a Jumbo near here that is below a parking garage and they have something similar, but it's an entirely passive system. The sloped movable walkway to the parking garage floor has this grooved pattern in it's surface anyway (so you don't slip) and the wheels have a similar pattern so they just sink into the grooves on the walkway. There's a brake pad next to each wheel just above the floor and as the wheel sinks into the grooves the brake pad touches the walkway locking it in place. At the beginning/end of the walkway there are these sloped protrusion into the grooves on the walkway that lift the cart out of the grooves as it reaches the end. No fancy locking system needed.