Back in the 1940s, Swiss engineers developed a new kind of zero-emission electric bus that used a large spinning flywheel to store energy rather than rechargeable batteries. The reason was simple—they wanted something quieter and cleaner, but most importantly they wanted a vehicle that wasn’t constrained by overhead power lines. Many Swiss cities at that time had trolley buses as public transport that ran on predetermined routes powered by electricity. But rails restricted movement and running overhead wires over new routes were prohibitively expensive. Battery technology too left a lot to be desired, just like today.

A demonstration of the Gyrobus charging up the flywheel at the electric loadpoint, in Ostend, Belgium, in 1985 on occasion of 100 years off vicinal railways. Photo credit: Smiley.toerist/Wikimedia