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...

Abstrac&--In an effort to relieve peak hour congestion on freeways, various ramp metering algorithms have been employed to regulate the inputs to freeways from entry ramps. In this paper, we consider a freeway system comprised of a freeway section and its entry/exit ramps, and formulate the ramp control problem as a dynamic optimal process to minimize the total time spent in this system. Within...

control freeway traffic in the United States, particularly in California. It is recognized that ramp metering can directly control the flow into the freeway (demand) and the average density immediately downstream, which indirectly affects the traffic upstream. After drivers enter the freeway, their collective behaviors are not controlled, which determines the traffic flow pattern. In addition, ...

Ramp meters in the Twin Cities have been the subject of a recent test of their effectiveness, involving turning them off for 8 weeks. This paper analyzes the results with and without ramp metering for several representative freeways during the afternoon peak period, depending on data availability. Seven performance measures: accessibility, mobility, equity, productivity, consumer surplus, trave...

Research recently conducted at the University of Central Florida involving crashes on Interstate-4 (I-4) freeway in Orlando, Florida led to the creation of new statistical and neural networks models that are capable of determining rear-end and lane-change crash risks along the freeway in real-time. For determining the rear-end crash risk, it was found that rear-end crashes occur within one of t...

The cell transmission model of a freeway is used to compare four congestion-reducing schemes: (R) ramp control only; (T) one lane is tolled and ramps are uncontrolled; (B) bottlenecks are tolled and ramps are uncontrolled; and (RB) ramps are controlled and bottlenecks are tolled. In the base case, ramps are uncontrolled and there are no tolls. It is found that (T) is inefficient and may leave a...

When implementing ramp metering in the context of freeway networks, traffic can spontaneously re-route due to the applied control actions. Although this re-routing can have an important impact on the resulting traffic situation in the traffic network and on the performance of the traffic network as a whole, re-routing is not automatically included in current model predictive frameworks for free...

This paper discusses the optimal coordination of variable speed limits and ramp metering in a freeway traffic network, where the objective of the control is to minimize the total time that vehicles spend in the network. Coordinated freeway traffic control is a new development where the control problem is to find the combination of control measures that results in the best network performance. T...

In this paper, we first review a localized ramp-metering strategy for freeways that achieves the goal of reducing the spatial and temporal span of traffic congestion, using locally available information. The control scheme is composed of a switching mainline-traffic responsive ramp-metering controller that adapts to the different traffic dynamics under different congestion conditions—free-flow ...

This paper proposes a nonlinear approach for designing traffic responsive and coordinated ramp control using a self adapting fuzzy system. The traffic responsive metering rate is determined every minute by an adaptive fuzzy logic algorithm. The coordination between multiple on-ramps is ensured by the integration of a common input into all ramp controllers upstream of a bottleneck and a periodic...