The first of July 1952, the moped was legislatively excluded from existing restrictions for heavier two-wheeled motorized vehicles. A driver/owner of a “bicycle with auxiliary engine” – this was the original denomination of the vehicle – thus needed no registration, driver’s license or insurance, nor pay any vehicle tax. The legislators did, however, postulate some technical requirements. Besides regulation of the engine, the vehicle should be “bicycle-like” and have pedals. It should thus be driven primarily by means of human, not mechanical, power (i.e., it was not supposed to be a lighter version of a motorcycle). In terms of social and economic goals, the state assumed workers to be the primary users, and a utilitarian use rather than one connected to pleasure and spare time. Very quickly, however, the moped lost all resemblance with the ordinary bicycle (except for the pedals). In a new legislation in 1961, the state yielded to the technical development. The moped no longer needed to resemble a bicycle or have pedals. Meanwhile, the moped also became more of a toy for boys – a vehicle for freedom – rather than the useful tool the state had wished for. In fact, we argue that the demands from user groups not foreseen played a crucial role in changing the legal technical requirements of the moped.This paper deals with the co-evolution, technically and institutionally, of the moped during the period 1952–75. Using a method inspired by evolutionary theory, the moped models released in Sweden in these years are grouped in “families” with distinctive technical features and accompanying presumed uses. We analyze this development using concepts from the theoretical fields of innovation studies and the history of technology