In all likelihood they're gonna mandate that 150cm2 arranged in stripes to be visible from all sides.
Equipment required for motorcyclesNot later than 1 January 2013, all drivers or passengers of a motorcycle with a cylinder capacity exceeding 125 cm3 or a vehicle of category L5e a capacity exceeding 15 kW, must wear a provided with a Equipment reflective, corresponding either to French standards or other standards to ensure an equivalent level of safety, provides the order of January 3, 2012.This equipment, in one or more parties must be a total surface area of at least 150 cm2.If this equipment is not built from the beginning to the garment, it is superimposed by any means (safety vest).The equipment must be worn on the upper body, with the exception of the helmet, from the belt line of the shoulders, so as to be visible to other road users.Note that in the course of 2012, the Ministry of Transport could also make the wearing of gloves and shoes suitable for driving a bike.