Approaches for classifying vehicles include generating a signal waveform from a signal in a single inductive loop generated by a passing vehicle. The signal waveform is compared to a first plurality of model waveforms. Each model waveform is associated with a respective class of vehicle. A first model waveform of the first plurality of model waveforms that matches the signal waveform is determined, and data indicating the respective class of vehicle associated with the first model waveform is output.