Investigating Potential Benefits of Vehicle Infrastructure Integration-Enabled Ramp Metering
Ramp metering is considered as one of the most effective approaches to improve freeway operations due to it’s capability of “proactive” control and management of traffic. However some severe limitations exist for current ramp metering algorithms:
- Acceptance of freeway traffic conditions as a “fixed” variable which eliminates opportunities to modify the freeway conditions to provide better situation for ramp merging, and
- Use of aggregated spot data collected from point sensors which results in inability to consider actual vehicle arrivals and spacing in setting on-ramp signals.
As new technology emerges, new opportunities that can address the limitations of existing ramp metering operations are becoming available. One such technology that has generated significant interest is Vehicle Infrastructure Integration (VII) which will allow detailed data coming from/going to individual vehicles and partial control capability over drivers’ functions as well. Therefore, developing new ramp metering algorithms that can fully utilize the capabilities of these emerging tools is desirable rather than just “fitting” new tools to old approaches.
With this background, in this research project, three VII-enabled local ramp metering algorithms (the variable speed limit, the lane changing advisory, and the GAP) were developed to fully utilize new VII opportunities, namely: a) detailed individual vehicular data and b) control capability. Evaluation of the developed algorithms was conducted using PARAMICS microscopic simulation of a heavily traveled freeway network in Orange County, California, for morning peak hours.
Evaluation results have revealed that VII has significant potential in improving ramp metering operations. More specifically, VII-enabled ramp metering algorithms improved the network performance by providing 4.3% more vehicle miles traveled while reducing vehicle hours traveled by 4.6%, which resulted in 9.3% higher average speeds. In addition, comparison among three developed algorithms showed that more active use of full VII opportunities would ensure better chances for the enhancement of ramp metering operations.
Key contributions resulted from this research work include:
- Development of first generation VII-enabled ramp metering algorithms to investigate new opportunities provided by VII,
- First quantification of the expected benefits of VII in ramp metering operations, and
- Implementation and evaluation of a lane control strategy in developing ramp metering algorithms.