Ramp metering and freeway bottleneck capacity

Warrants for ramp metering installation have been developed by a number of U.S. states. These warrants are generally simple and are based on the traffic, geometry, and safety conditions in the immediate vicinity of each ramp (local conditions). However, advanced applications of ramp metering use system-based metering algorithms that involve metering a number of on-ramps to address system bottlenecks. These algorithms have been proved to perform better compared with local ramp metering algorithms. This situation creates a disconnect between existing agency metering warrants to install the meters and the subsequent management and operations of the ramp meters. This study focused on assessing the need for system warrants in addition to local warrants for ramp metering installation to prevent traffic breakdown at bottleneck locations. A linear programming formulation combined with consideration of the stochasticity of bottleneck capacity was used to select the ramps to be metered on the basis of the system bottlenecks. The study found that the selection of these ramps for metering—in addition to those justified by local warrants—could delay the breakdown at the system bottleneck location and improve the performance of the freeway main line. Another important benefit of selecting ramps for metering based on system operations was its distribution of on-ramp delays because of metering of more ramps and thus to a reduction in the delay experienced on the ramps selected with the existing warrants that were based on local conditions.

Download Full-text

Effect of Time Gaps and Lane Flow Distributions on Freeway Bottleneck Capacity

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198106196500101 ◽

2006 ◽

Vol 1965 (1) ◽

pp. 2-11 ◽

Cited By ~ 5

Author(s):

James H. Banks

Keyword(s):

Bottleneck Capacity ◽

Freeway Bottleneck

Download Full-text

Integrated Variable Speed Limits Control and Ramp Metering for Bottleneck Regions on Freeway

Mathematical Problems in Engineering ◽

10.1155/2015/313089 ◽

2015 ◽

Vol 2015 ◽

pp. 1-17 ◽

Cited By ~ 6

Author(s):

Ming-hui Ma ◽

Qing-fang Yang ◽

Shi-dong Liang ◽

Zhi-lin Li

Keyword(s):

Traffic Flow ◽

Traffic Congestion ◽

Ramp Metering ◽

Variable Speed ◽

Speed Limits ◽

Advanced Control ◽

Variable Speed Limits ◽

Travel Delay ◽

Freeway Bottleneck

To enhance the efficiency of the existing freeway system and therefore to mitigate traffic congestion and related problems on the freeway mainline lane-drop bottleneck region, the advanced strategy for bottleneck control is essential. This paper proposes a method that integrates variable speed limits and ramp metering for freeway bottleneck region control to relieve the chaos in bottleneck region. To this end, based on the analyses of spatial-temporal patterns of traffic flow, a macroscopic traffic flow model is extended to describe the traffic flow operating characteristic by considering the impacts of variable speed limits in mainstream bottleneck region. In addition, to achieve the goal of balancing the priority of the vehicles on mainline and on-ramp, increasing capacity, and reducing travel delay on bottleneck region, an improved control model, as well as an advanced control strategy that integrates variable speed limits and ramp metering, is developed. The proposed method is tested in simulation for a real freeway infrastructure feed and calibrates real traffic variables. The results demonstrate that the proposed method can substantially improve the traffic flow efficiency of mainline and on-ramp and enhance the quality of traffic flow at the investigated freeway mainline bottleneck.

Download Full-text