Relationships between ramp metering and sprawl

This paper explores impacts of ramp metering on urban land use. A regression-based transportation model is developed to capture changes in accessibility caused by ramp metering on a highway network. A Land Use Change Indicator (LUCI) model is modified to estimate how the spatial distribution of employment and housing would change in response to the redistributed accessibility in five hypothetical urban areas with various initial land use patterns. Accessibility will be improved in almost all areas in a city with ramp metering, but meters affect land use patterns in various ways depending on initial land use conditions. Ramp metering can exacerbate decentralization, but not necessarily sprawl.Ramp metering, Land use, Urban sprawl, Decentralization

Dynamic multi-ramp metering control with simultaneous perturbation stochastic approximation (SPSA)

Ramp metering was proven to be a viable form of freeway traffic control strategy, which could eliminate, or at least reduce, freeway congestion. In this study, the development of ramp metering control strategies, models, and constraints (e.g., meter locations, ramp storage capacities, lower and upper bounds of ramp metering rates) are discussed in detail. The pre-timed and demand/capacity metering control strategies were first evaluated, while the potential metered ramps were determined. A Simultaneous Perturbation Stochastic Approximation (SPSA) algorithm is proposed to dynamically optimize multiple-ramp metering control by maximizing the total throughput subject to a number of constraints. The ramp metering rates subject to dynamic traffic conditions and capacity constraints are considered as decision variables in the SPSA algorithm. Based on the collected geometric and traffic data, a CORSIM model was developed to simulate traffic operation for the study site. The potential benefit of the dynamic multi-ramp metering control model under time varying traffic condition was simulated and evaluated. The increased total throughput and reduced total delay were observed, while the traffic conditions suitable for implementing ramp metering control were suggested. The developed dynamic multi-ramp metering control with SPSA algorithm has demonstrated its effectiveness to improve freeway operation

A Novel Ramp Metering Approach Based on Machine Learning and Historical Data

The random nature of traffic conditions on freeways can cause excessive congestions and irregularities in the traffic flow. Ramp metering is a proven effective method to maintain freeway efficiency under various traffic conditions. Creating a reliable and practical ramp metering algorithm that considers both critical traffic measures and historical data is still a challenging problem. In this study we use machine learning approaches to develop a novel real-time prediction model for ramp metering. We evaluate the potentials of our approach in providing promising results by comparing it with a baseline traffic-responsive ramp metering algorithm.Comment: 5 pages, 11 figures, 2 table

A Compartmental Model for Traffic Networks and its Dynamical Behavior

We propose a macroscopic traffic network flow model suitable for analysis as a dynamical system, and we qualitatively analyze equilibrium flows as well as convergence. Flows at a junction are determined by downstream supply of capacity as well as upstream demand of traffic wishing to flow through the junction. This approach is rooted in the celebrated Cell Transmission Model for freeway traffic flow. Unlike related results which rely on certain system cooperativity properties, our model generally does not possess these properties. We show that the lack of cooperativity is in fact a useful feature that allows traffic control methods, such as ramp metering, to be effective. Finally, we leverage the results of the paper to develop a linear program for optimal ramp metering

Traffic Management Systems

This study uses regression analysis to evaluate long-run traffic management system performance. Three important traffic management systems in the Twin Cities metro area - Ramp Metering, Variable Message Signs (VMS), and Freeway Service Patrol (the Highway Helper Program) were evaluated with multiple regression models to predict link speed and incident rate. We find that ramp meters increase freeway link speed and reduce incident rate. Freeway Service Patrols increase link speed when incidents are present. The results for variable message signs are ambiguous.Traffic management system; Traffic system performance; Before-and-after study; Ramp Metering System; Variable Message Signs (VMS); Freeway Service Patrol; Highway Helper Program.

Ramp metering and freeway bottleneck capacity

The objective of this study is to determine whether ramp meters increase the capacity of active freeway bottlenecks, and if they do, how. The traffic flow characteristics at twenty-seven active bottlenecks in the Twin Cities have been studied for seven weeks without ramp metering and seven weeks with ramp metering. A series of hypotheses regarding the relationships between ramp metering and the capacity of active bottlenecks are developed and tested against empirical traffic data. It is found that meters increase the bottleneck capacity by postponing and sometimes eliminating bottleneck activations (a 73 percent increase in the duration of the pre-queue transition period), accommodating higher (2 percent) flows during the pre-queue transition period, and increasing queue discharge flow rates after breakdown (3 percent). The two-capacity hypothesis about flow drops after breakdown was also examined and results strongly suggest the percentage flow drops at various bottlenecks follow a normal distribution (mean 5.5 percent, standard deviation 2.3 percent). The implications of these findings on the design of efficient ramp control strategies are discussed, as well as future research directions.transportation, travel behavior, congestion, ramp meters

Travel Time Variability After A Shock: The Case Of The Twin Cities Ramp Meter Shut Off

Ramp meters in the Twin Cities were turned off for 8 weeks in the Fall of 2000. This paper analyzes travel time variability with and without ramp metering for several representative freeways during the afternoon peak period. Travel time variability is generally reduced with metering. However, it is found that ramp meters are particularly helpful for long trips relative to short trips. The benefits from reducing travel time variability with meters are on the order of 37% of the benefits from reducing average travel time.Freeway Operations, Ramp Meters, Travel Time Variability Before-and-after study; Ramp Metering System; Variable Message Signs (VMS); Freeway Service Patrol; Highway Helper Program.