Gyrobus

The concept of a flywheel-powered bus was developed and brought to fruition during the 1940s by Oerlikon (of Switzerland), with the intention of creating an alternative to trolleybuses for quieter, lower-frequency routes, where full overhead-wire electrification could not be justified.

Fully charged, a gyrobus could typically travel as far as 6 km (3.7 mi) on a level route at speeds of up to 50 to 60 km/h (31 to 37 mph), depending on the total weight of passengers, as top speeds varied as passenger levels varied from stop to stop.

The installation in Yverdon-les-Bains (Switzerland) sometimes saw vehicles needing to travel as far as 10 km (6.2 mi) on one charge, although it is not known how well they performed towards the upper end of that distance.

[2] In the 1980s, Volvo briefly experimented with using flywheels charged by a small diesel engine and recharged via braking energy.

Here there were 12 vehicles (although apparently some reports suggest 17), which operated over four routes, with recharging facilities being provided about every 2 km (1.2 mi).

Other problems included breakage of gyro ball bearings, and high humidity resulting in traction motor overload.

The Ghent to Merelbeke route was intended to be the first of a proposed multi-route network; instead, its gyrobuses stayed in service for only three years, being withdrawn late autumn 1959.

Since 2005, Dresden, Germany has had an Autotram, a vehicle that uses a fuel cell as its main source of energy and a small flywheel for regenerative braking only.