Freeway On-Ramp Design Criteria for Ramp Meters with Excessive Queue Detectors

Abstract

Guidelines were developed for designing freeway on-ramps in which ramp metering is envisioned. More specifically, design issues were probed for ramps in which the ramp meter utilizes a queue detector to identify and prevent a queue of vehicles from blocking the upstream intersection. First, the benefits of ramp metering operation were delineated, and general design considerations were then drawn up. Finally, design criteria were developed for three distance requirements for freeway on-ramps: safe stopping distance, storage distance, and acceleration distance.

Integrated variable speed limit and ramp metering control study on flow interaction between mainline and ramps

“…For RM implementation, a signal control strategy, namely ''single-lane one car per green,'' was applied in the signal-state generator. It allows one vehicle to enter the freeway during each signal cycle with a minimum duration of 4.5 s. 24 An uncontrolled single-lane onramp is capable of a throughput of 1800 veh/h. The minimum admissible ramp flow is typically 200-400 veh/h.…”

Optimizing the efficiency and equity of traffic flow : development of a control strategy for freeway corridors using dynamic Bayesian decision networks

“…75). Chaudhary and Messer (2002) also allude to this role: "A secondary objective of ramp metering is to introduce controlled delay (cost) to vehicles wishing to enter the freeway and, as a result, reduce the incentive to use the freeway for short trips during peak hour" (pg. 80).…”

“…There is a general recognition in the literature that one of the benefits of ramp metering is its ability to break up vehicle platoons at entrance ramps, smoothing traffic operations in the vicinity of the merge and improving safety. For example, Chaudhary and Messer (2002) claim that one of the three main objectives of ramp metering is to break up platoons of vehicles released from an upstream traffic signal, in order to provide a safe merge operation at the freeway entrance. Despite this recognition, however, much of the literature focuses on the congestion relief provided by ramp meters; any benefits from reduced turbulence in the merge area are considered merely a positive by-product of the metering process.…”

“…• Sufficient storage for vehicles queued at the meter to prevent spillback onto the arterial system (storage distance) (Chaudhary and Messer 2002) Depending on the control strategy, a number of detectors are needed to track vehicle movement through the metered zone:…”