Vehicle Modal Activity on Freeway Loop On-ramps: Inputs to the Development of a Ramp Drive Cycle to Determine the Vehicle Emissions Impacts of Ramp Metering

The goal of the study is to collect a comprehensive set of freeway and on-ramp operational data for the assessment of ramp metering systems. This paper is a presentation of data and initial findings for vehicle operations on loop ramps; a small subset of the larger project. The results reported here focus on the changes in modal activity (e.g. speed/acceleration) that occurred on two of the study area freeway loop on-ramps as a function of meter operation. The study showed that vehicles on the two freeway loop on-ramps assessed in this paper displayed increase levels of modal activity that may result in associated increased levels of vehicle emissions. This analysis was limited to ramp activity and associated with only two ramp locations. Therefore, the extension of these results to other freeway on-ramps or to the evaluation of ramp metering systems as whole is also limited (the larger study will address overall system impacts and is due to be completed in April 2000). The analyses presented in this paper do provide initial evidence that ramp metering will impact vehicle activity on ramps and that the activity within each condition (metered versus nonmetered) is reasonably consistent. This also provides the initial steps for developing a ramp drive cycle for use in the detailed modeling of freeway on-ramp emissions. Continuing research in the area will assess the specific emissions impacts and the system wide air quality effects.