Doctor of Philosophy (PhD)
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Freeway operations, Ramp metering, Mobility
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Transportation agencies are implementing traffic management strategies to improve mobility and safety on freeways. Ramp metering is a traffic management strategy deployed to mitigate congestion on freeways using traffic signals installed at entrance ramps to control and regulate vehicle entry onto the freeway mainline. Estimating the mobility benefits of ramp metering is critical to determine the strategy's effectiveness and inform the decision-making process regarding its deployment.
However, the extent of the impact of ramp metering on recurrent congestion varies across studies. Among the reasons for the inconsistencies are the limitations of conventional methods for evaluating benefits, including the before-and-after approach, shutdown experiment, and traffic simulation. In addition to alleviating recurrent congestion, ramp metering has the potential of improving traffic conditions during non-recurrent congestion. Few agencies have used ramp metering to reduce non-recurrent congestion resulting from traffic incidents and adverse weather. Nonetheless, the ramp benefits during non-recurrent congestion are not well researched.
This research aimed to estimate the mobility benefits of ramp metering during recurrent and non-recurrent congestion. To achieve the research goal, the study evaluated the effects of ramp metering on travel time reliability, the impact of ramp metering on traffic conditions upstream of a crash location, and the effects of ramp metering on traffic conditions during rainy weather. The research used data collected when ramp metering signals (RMSs) are activated and during unintentional RMSs’ downtime to account for the limitations of the conventional methods for estimating benefits.
Results of the analysis focusing on recurrent congestion showed that ramp metering significantly improves travel time reliability. It was estimated that ramp metering increased travel time reliability by 23% during moderate recurrent congestion and by 28% during severe recurrent congestion.
The analysis during non-recurrent congestion showed that ramp metering has varying impacts on traffic conditions upstream of a crash location. Ramp metering significantly affected traffic conditions upstream of a crash location during peak periods and daytime off-peak periods. Activating RMSs during rain in daytime off-peak periods and peak periods positively affected traffic conditions downstream of the entrance ramps. Based on the estimated benefits, agencies could establish criteria for selecting when and which RMSs to be activated to alleviate non-recurrent congestion. The estimated benefits could also be used when assessing the cost-effectiveness of future deployment of RMSs.
Haule, Henrick Joseph, "Estimation of the Mobility Benefits of Ramp Metering" (2021). FIU Electronic Theses and Dissertations. 4723.
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