1. Method for classifying vehicles in which vehicles passing through a radar cone formed by radar radiation are measured, said vehicles having surfaces on which radar radiation impinges thus reflecting said radar radiation, and wherein measurement signals with frequencies corresponding to a Doppler shift are generated, said method comprising: a) arranging, at a vertical installation height relative to a surface of a roadway and at a horizontal acute installation angle relative to an edge of the roadway, an angle-resolving radar device for yielding measurement signals which have frequencies corresponding to the Doppler shift and from which radial distances, object angles and radial velocities can be derived, b) emitting a radar beam from said radar device forming a radar cone, and acquiring measurement signals from at least one vehicle traveling through the radar cone at a plurality of measuring times during a measurement time period, c) storing the frequencies of the acquired measurement signals of measured vehicles as functions over the measurement time period, and forming a spectrogram for every measured vehicle, d) checking the spectrograms for assessment regions with maximum bandwidth of the frequency, and at least one measuring time is determined in the assessment region as an assessment time, e) comparing said assessment regions with assessment regions of stored spectrograms for different vehicle classes, and assigning the most similar spectrogram in order to classify the vehicles traveling through said cone, and f) deriving object angles from the measurement signals at the at least one assessment time within the assessment regions with maximum bandwidth, wherein the respective derived object angles for the respective assessment time are stored in each instance as a function over the frequency, and the curve of the function is compared with comparison models stored for different vehicle classes in order to verify the classification of vehicles.