The Paris police force was completely re-organized after the fall of Napoleon III and the Commune; the "sergents de ville" were replaced by the "gardiens de la paix publique" (Guardians of the Public Peace), which by June 1871 had 7,756 men under the authority of the Prefect of Police named by the national government. Following a series of anarchist bombings in 1892, the number was increased to 7,000 guardians, 80 "brigadiers" and 950 "sous-brigadiers". In 1901, under the prefect Louis Lépine, in order to keep up with the technology of the time, a unit of policemen on bicycles (called the "hirondelles" after the brand of the bicycles) was formed. They numbered 18 per arrondissement and reached 600 by 1906 for the whole city. A unit of river police, the "brigade fluviale", was organized in 1900 for the Universal Exposition, as well as a unit of traffic police who wore a symbol of a Roman chariot embroidered on the sleeve of their uniform. The first six motorcycle policemen appeared on the streets in 1906.