The transyt vehicle dispersion model in frequency domain

This paper describes the dispersion of vehicles along a road on departure from a signalised intersection. The dispersion is analysed in both the time and frequency domains. The modelling of the dispersion is based on a recursive formula currently adopted in transyt, a traffic signal optimisation program. The model in the time domain is well understood and has been successfully employed for traffic control. A new approach to the same model in the frequency domain is presented. It is argued that traffic dispersion in the frequency domain is due to the difference in the attenuation of various frequency components in the input wave form. A traffic link is analysed as a frequency dependent transfer function. Equations for the amplitude and phase component of the transfer function are derived. Interpretations of their characteristics are found to correlate well with existing traffic control practice. An example is used to illustrate the frequency domain analysis (a).