At Tron (Magic Kingdom), locker use is mandatory. There is no storage available on the vehicles ? at all. In the queue, you'll find lockers for storing your loose items before you board. Lockers can be opened using either a MagicBand or a ticket card (MagicMobile will not work), and are about a cubic foot.

For the TRON Lightcycle / Run attraction at Magic Kingdom, Disney utilizes a sophisticated, double-sided digitized locker system located mid-queue. These lockers are complimentary and are accessed by tapping your MagicBand, MagicBand+, or physical park ticket card; any locker with a lit-up numerical display is available for use. Because the Lightcycle ride vehicles require guests to lean forward in a motorcycle-style position, almost all bags and large loose items must be placed in these lockers before you reach the boarding platform. However, for essential small items like cell phones, wallets, or glasses, there is a small, secure compartment built directly into the dashboard of each individual Lightcycle. Once the ride is over, you exit into a different area where you access the "back" side of the same locker to retrieve your larger belongings. If you do not have a physical MagicBand or card, a Cast Member will provide a temporary locker card at no charge to ensure your items are safely stored during the high-speed race.