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The great increase in car ownership has led to the daily recurrence of traffic congestion. Thus, traffic mobility, safety and emission concerns have become the most serious challenges for transportation researchers. To mitigate traffic congestion, a variety of proactive traffic-control strategies, such as ramp metering (RM), have been intensively investigated and deployed. With the aim of improving freeway traffic conditions, RM regulates the on-ramp flows dynamically in response to dynamic road conditions. However, most early RM strategies focus on optimising the traffic from one single aspect. This paper presents an RM control algorithm that predicts and evaluates the RM-controlled future traffic states. The impact of RM control was evaluated using a macroscopic traffic-flow model. The designed RM control algorithm possesses a multi-objective optimisation module, which improves the traffic network from the aspects of mobility, safety and emissions. The designed algorithm is evaluated through simulation and calibrated using field data collected over an 11 km major freeway stretch in Edmonton, Alberta, Canada. The comparison of the proposed algorithm-controlled scenario and the uncontrolled scenario shows that the proposed RM control algorithm can effectively relieve traffic congestion, improve safety and reduce carbon emissions concurrently. [ABSTRACT FROM AUTHOR]

Abstract Researchers seeking to identify public policies to reduce automobile use have frequently compared characteristics such as population density and freeway provision across metropolitan regions to identify differences, their causes, and their implications for automobile reliance. One frequent comparison has been between metropolitan regions in Canada and the United States given their similar contexts but differing modal shares. However, past studies have produced inconsistent findings with respect to how Canadian and American metropolitan regions can be distinguished with respect to population densities and freeways. In response to methodological concerns with past research, this paper measures population densities and freeways in the 57 North American metropolitan regions with at least one million residents. Two spatial scales (metropolitan region and central core) are used to measure overall density, population-weighted average census tract density, and density of the top 5% of the population. These same spatial scales are also used to measure the absolute and per capita quantities of freeway lanes. The paper provides methodological explanations using Los Angeles and Vancouver as examples. While Canada's metropolitan regions are commonly portrayed as denser and less auto-oriented than their US counterparts, the six largest of Canada's metropolitan regions do not have population higher densities and fewer freeways than all of the 51 largest US metropolitan regions. Indeed, this generalization holds only when individual results are combined to produce national averages, as there are numerous US metropolitan regions that have density and freeways in the same range as Canada's metropolitan regions. The paper discusses some of the differences and recommends approaches for future comparative research into the causes of variation in transport and land use. [ABSTRACT FROM AUTHOR]