On-ramp metering based on three-phase traffic theory

摘要

The probabilistic nature of traffic breakdown and freeway capacity at an on-ramp bottleneck is discussed based on the author's three-phase traffic flow theory. It is stressed that the probabilistic nature of traffic breakdown leads to a limitation for reliable applications of free flow control approach in which free flow should be maintained at the bottleneck. It is explained that earlier traffic flow models and related simulation tools cannot explain and cannot predict traffic breakdown at the bottleneck as it is observed in empirical (measured) data. For this reason, the related simulations of freeway control and management strategies cannot predict many of the freeway traffic phenomena that would occur through the use of these strategies. Explanations of this critical conclusion are made. An introduction to microscopic freeway simulations of freeway control in the context of three-phase traffic theory is outlined, which shows and explains empirical features of traffic breakdown and resulting congested patterns. In the following parts Ⅱ and Ⅲ, the consequences of probabilistic nature of traffic breakdown for on-ramp metering strategies are discussed. Firstly (part Ⅱ), a critical analysis of the well-known ALINEA method for feedback on-ramp metering is performed. In part Ⅲ, a possible solution of the on-ramp metering problem - a recent congested pattern control approach (ANCONA) -is considered. Parts Ⅱ and Ⅲ will be published in the February and March issues of TEC.