My colleague, Meijun Liu, and I developed a model to evaluate the current and future operating conditions of a suburban highway in the greater Philadelphia area in the United States. The highway US 422 already experiences high levels of congestion and is located in a growing area where traffic volumes are expected to increase. For this reason, finding solutions to alleviate the traffic issues is a priority for the Pennsylvania Department of Transportation (PennDOT). A secondary objective was to conduct sensitivity tests using a 25-mile segment of US 422. First, peak-period traffic conditions were evaluated by conducting simulations using PTV Visum and PTV Vissim. The software helps with identifying the optimum strategies that can improve the operating conditions of the corridor. We couldn’t have achieved the desired objective within the short time available without using PTV Visum and PTV Vissim.
Data collection, analysis and results
First, I collected peak period data on the mainline, ramps, and the intersections. Data also included traffic counts and turning movements as well as traffic control details at the intersections such as signal timing. AM peak-time data were collected from 6AM to 10AM while PM peak-time data were collected from 3PM to 7PM. We then used the subcut process to clip the highway network from the regional model, which was originally developed in PTV Visum. Hourly trip tables for the peak periods were developed and refined in PTV Visum and supplemented with Longitudinal Employer-Household Dynamic (LEHD) data. The hourly trip tables were stitched together into a single PTV Vissim file representing the peak period. PTV Vissim’s Dynamic Traffic Assignment was then used to develop the vehicle routing details. Furthermore, calibration was performed to ensure that the PTV Vissim networks accurately reflected typical traffic conditions. We will use these models to perform various scenario testing and analysis to examine performance under different conditions. We expect that the results will help us to identify a unique and optimum operational strategy that will improve mobility along the very busy transport corridor. The approach we used for this project was very effective in creating the model. The integration between PTV Visum and PTV Vissim allowed for efficient model development and saved a lot of time. Even large highway models can be produced in timely manner. We will certainly use this approach for future projects.
“One of the best traits of PTV is that they listen to their customers. The software is continually being updated and improved based on user feedback.”
Comprehensive data forms the basis for informed decisions
The primary strength of the software is that it allows for comprehensive data collection from the simulations analysis, when compared with actual field data, and can be used confidently as a measure of effectiveness. Performance measures, taken as output from the simulations, permit quantifiable comparisons between scenarios. This allows our stakeholders to make informed decisions about potential improvement projects and weigh the benefit or potential disbenefit of any scenario. The dynamic functionality of the software streamlined our workflow. We were able to deliver products with fewer resources. With the improvement in integration between PTV Visum and PTV Vissim, we are now able to conduct large highway studies more quickly than before. The origin/destination patterns included in a regional model subcut can be transferred into PTV Vissim. This has shortened the process for developing a network’s routing structure. The reporting tools in PTV Vissim are also important to know when the model is calibrated to predetermined standards.
3D animations effectively visualize scenarios and their impacts
The 3D animations are an especially effective tool for communicating a problem. In the early days, we would produce tables upon tables of performance measure data and several screen shots of the simulation. These were typically summarized into reports and given as project deliverables. Now, with the ease of developing 3D animations, we can quickly and more effectively show the impact of a condition that is easy to understand. Additionally, PTV Vissim allows for multi-modal development such as having private vehicles, transit, and pedestrians in a single model. But it is the ability to simulate the interaction between the different modes that demonstrates the true value of the software. In addition, new functionalities, especially the autonomous vehicle features, prepare us for planning the future.
