As the number of vehicles in urban areas is ever increasing, it has been a major concern of city authorities to facilitate effective control of traffic flows in urban areas. In this context, Vehicular traffic density state estimation provides an important information for road planning, intelligent traffic routing, adaptive traffic signal control, etc. The Traffic Density State estimation is fast emerging field based on an acoustic signal. Developing geographies like Asia where the traffic condition is chaotic and non-lane driven, intrusive techniques may be inapplicable. The traffic density state condition at any location is depends upon the mixture weighting of spectral components of various vehicular acoustics. This book considers the problem of vehicular traffic density state estimation using statistical framework that uses the cumulative acoustic signal from a roadside installed microphone, to classify the vehicular traffic density into Low (free flow) state, Medium flow state, Heavy state etc. and various application based on it.