Created by Chris Burden, and currently showing at LA’s County Museum of Art (LACMA):
https://www.lacma.org/art/exhibition/metropolis-ii

It works as a miniature, kinetic city using magnets and conveyor belts to power over 1,100 toy cars on 18 roadways, with gravity providing most of the downhill momentum… all managed by operators and conservators for continuous motion.

• Power System: Three electric conveyor belts, embedded with magnets, pull the cars to the top of the sculpture.
• Gravity & Friction: Once released from the conveyor, cars race down the tracks, using gravity and momentum; Teflon-coated, beveled tracks and friction-inducing brushes help manage speed and flow.
• Vehicles: 1,100 custom-made toy cars (and model trains/trolleys) designed for durability, with magnets on their undersides.
• Architecture: An intricate grid of steel, wood, LEGO, and other materials forms buildings and roadways, with an operator stationed in the center to ensure smooth operation. --Gemini

Looking at the site brochure (link above): the exhibit runs for 5-6 daily half-hour shows, 4x per week, with one rest day, and two maintenance days(!)