Mitigation of traffic pollution emissions in the built environment: a real-time flow actuated tool for on ramp management

Highways are increasingly common in today's built environment and contribute majorly in environmental pollution. Mitigation strategies have been developed to decrease the traffic volume but have not been as effective, since the need for car use in transportation keeps growing. The key is to create an efficient road network which will allow the same traffic volume to flow through, with a reduced environmental impact. The main goals of this paper include the investigation and evaluation of alternative ramp metering scenarios on a freeway on-ramp and the development of a "smart" signal controller, with the use of PTV Vissim microsimulation software. A specific area was selected for the implementation of this study. More precisely, interchange K8 on the Ring road of Thessaloniki was chosen, in which, measurements of traffic volume were taken using a drone to record the traffic. Using the Vissim platform, a software model was created and evaluated to determine its accuracy compared to the existing situation. Different scenarios were developed, and the function of the interchange was observed, as well as the percentage of emissions. In the first set of scenarios, the traffic volume was increased by certain percentage and the results were collected and examined. Next, two new scenarios with the use of ramp metering were developed and a traffic signal was placed on the on-ramp. In the first of these two scenarios, a traffic signal light with a fixed-time traffic program was placed, whereas in the second one, a vehicle-actuated signal light was created, with the use of the VisVAP add-on. A flow chart was generated and used to program the signal light, so that each time high traffic volume was detected by the detectors that were placed in the expressway, the red light was activated. After all the scenarios were created and examined, certain KPI's regarding CO, NOx and VOC emissions and fuel consumption, as well as other traffic related data, were collected and used for the overall evaluation. The results from the use of the ramp meter, either the fixed-time or the vehicle-actuated, showed that a ramp meter can be very useful in the improvement of the traffic conditions and may have a positive environmental impact, by reducing emissions even up to 70%.