Automatic measurement of traffic variables for intelligent transportation systems applications

This paper presents a methodology for automatic measurement of major traffi c variables for Intelligent Transportation Systems applications (ITS) in re al-time. It is an illustration of the integration of theory, measurement, a nd application. Such effort has been overlooked since the advent of ITS due to the number of different disciplines involved. The inductive methodology adopted in this study includes the development of a new dynamic traffic fl ow model which is based on the characteristics of the stochastic vehicle co unting process and the principle of conservation of vehicles. The model est imates spatial traffic variables, such as link travel times, as a function of time directly from flow measurements. It satisfies the traffic dynamics through a new form of the equation of conservation of vehicles. Analysis re sults show that the estimates are in qualitative and quantitative agreement with empirical data aggregated at 2-min intervals. The advantages of this inductive model include real-time applicability, computational efficiency, and transportability over traditional deductive models such as continuum fl ow models. It appears to be promising in applying to real world problems. ( C) 1999 Elsevier Science Ltd. All rights reserved.