An analysis of real-time control measures for calculating urban freeway operation

Abstract

To optimize movement in a traffic system, automatic surveillance methods are being used in the development of real-time control systems. Since the freeway has a significant effect on the operation of a traffic system, this dissertation was directed toward the development of research tools for use in real-time control of a freeway system. Various traffic measures were investigated as means of measuring the quality of freeway operation, and techniques for determining the occurrence of certain traffic situations were evaluated. Data collection and computer analyses were made by a digital process computer interfaced with loop detectors at the Gulf Freeway Surveillance and Control Office in Houston, Texas. For evaluation of the measures and techniques, freeway operation was divided into three levels of regular operation: light flow, moderate flow, and peak flow. Data bases of one minute, three minutes, and five minutes were evaluated, and data were updated each minute. Data were collected from the middle lane detectors only to investigate the reliability of a minimal detection system. Of the 52 measures investigated, the results showed that only twelve measures are real-time control measures (RTC measure). A thirteenth RTC measure, Wave Velocity, was proposed from the hydrodynamic theory. The characteristics of expected change between consecutive, updated values and the distribution curves for the three levels of operation were determined for each RTC measure. The level of operation (or LO) technique was proposed as a measure of changes between the levels of regular operation. This technique was evaluated using Wave Velocity and resulted as a reliable method of determining changes in levels of operation. ...