This assembly, which includes a ground level power supply system of the type using conduction, including conductive tracks arranged on a roadway, and an electric vehicle, capturing electric energy from said tracks it moves on the roadway, is characterized in that the power supply system includes a ground level antenna, configured so as to have a constant radiation chart along a longitudinal axis of the roadway and emitting a positioning signal, and in that the electric vehicle includes an on board antenna and an on board module, connected to the on board antenna and capable of determining a lateral position of a center of the on board antenna relative to the longitudinal axis from the positioning signal captured by the on board antenna.