Disneyland's Monorail made its debut in 1959. The accordion gap-fillers have been in my memory since then, when I got to experience the system firsthand.
This technology dates to at least 1951, when intercity bus lines used it on the West Coast. I didn't come along until the year after.
It remains a bird in hand.
https://d23.com/a-to-z/monorail/