Tag Archives: traffic monitoring

Traffic and Safety

Building More Accurate Traffic Modeling for Twin Cities Construction Projects

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MnDOT is exploring different software options for developing a “mesoscopic dynamic traffic model” that can more accurately predict road construction impacts than current macroscopic models like the Twin Cities Regional Travel Demand Forecasting Model.

“Dynamic traffic assignment is an emerging model type, and there are a lot of software platforms with different methodologies. MnDOT was interested in reviewing their pros
and cons,” said Jim Henricksen, Traffic Forecaster, MnDOT Metro District, who helped lead a recent research project that analyzed different software packages.

“A team maintains the Twin Cities Regional Travel Demand Forecasting Model. Any mesoscopic model would require a similar maintenance effort to keep the model from becoming obsolete as construction adds new lanes,” said John Hourdos, Director, Minnesota Traffic Observatory, University of Minnesota, and principal investigator for the study.

What Was the Need?

Traffic modeling is a valuable tool used in transportation planning to predict the impacts of new construction or maintenance projects. MnDOT currently has modeling tools available in two scales: macroscopic and microscopic. Macroscopic-scale planning level tools such as the Twin Cities Regional Travel Demand Forecasting Model predict driver route choice and the number of drivers that will travel on a given road at a given time. Microscopic-scale traffic simulation, on the other hand, models driver behaviors such as gap acceptance or acceleration rates. MnDOT uses microscopic-scale simulation to plan capacity-increasing projects, but the tool is only feasible on the corridor level because generating the simulation requires a large amount of data and computing power.

To bridge these two scales, MnDOT is developing a mesoscopic-scale dynamic traffic assignment (DTA) model for the Twin Cities. This model falls between microscopic- and macroscopic-scale modeling in scope and complexity. It simulates the movement of individual vehicles based on traffic flow equations rather than driving rules, which requires less detail and computing time than a microscopic simulation and can be used over a wider area. MnDOT will use this model for applications such as staging construction seasons to minimize the disruption caused by multiple large projects, or coordinating traffic modeling across the road networks operated by MnDOT, counties and cities.

To assist in developing this system, MnDOT needed information about the capabilities of available modeling software packages in addition to the needs, desires and restrictions of the agencies and consultants who will be using the model.

What Was Our Goal?

The goal of this project was to better understand the capabilities of commercially avail-able modeling software packages to address MnDOT’s modeling and simulation needs.

What Did We Do?

Investigators interviewed stakeholders about their understanding of and need for mesoscopic traffic simulation and DTA. Stakeholders included individuals who have used or requested data from the Twin Cities Regional Travel Demand Forecasting Model maintained by the Metropolitan Council. Investigators also reviewed four case studies of mesoscopic DTA models used in Manhattan; San Francisco; Detroit; and Jacksonville, Florida.

To supplement the findings from the interviews and case studies, investigators conducted a comprehensive review of the claimed capabilities of six commercially avail-able traffic simulation software packages: TransModeler, Aimsun, DynusT/DynuStudio, Dynameq, Cube Avenue and Vissim. Investigators didn’t test the software, but instead reviewed manufacturers’ documentation and literature to identify limitations of their methods and whether those methods are applicable to MnDOT’s needs.

Traffic in a highway work zone.
DTA can aid in staging multiple major construction projects in the Twin Cities to minimize the disruption they cause to travelers.

What Did We Learn?

To compare the capabilities of the various simulation software packages, investigators created a matrix that included comprehensive notations about a software package’s claimed features that may not fully meet MnDOT’s simulation needs. For example, some software packages claim to model actuated signals, but they create models based on Highway Capacity Manual assumptions rather than real-world conditions.

DynusT is the most commonly used simulation program, possibly because it is open-source and the easiest software to use, although it requires DynuStudio, a commercial graphical user interface and data management system. DynusT also has some limitations, such as not considering the individual lanes in each roadway segment, which would limit its effectiveness in modeling roads where individual lanes have imbalanced densities.

Most interviewees had only limited experience with mesoscopic modeling. Incorporating traffic signals in a simulation network is a significant challenge, according to interviewees, because currently a database of signal timings isn’t available.

While all four of the DTA case studies reviewed required more data, calibration and validation than older models, each of the developers reported that these challenges had been mitigated, and the models created could answer complex questions that previous models couldn’t.

What’s Next?

Traffic simulation and modeling is a fast-developing field, particularly mesoscopic-scale modeling. Each of the software packages reviewed in this project has had at least two new versions in the past 18 months, and while their modeling approaches are fundamental to the software in some cases, in other cases capabilities will be added or improved as software develops.

The foundation of a mesoscopic model for the Twin Cities has been built and tested in Transmodeler (with significant pro bono work from the software developer). However, MnDOT has also used its existing DynusT model for several projects beyond its initial purpose, and the agency will use the information gathered in this project to determine which approach is more practical for MnDOT and its consultants based on cost, capabilities and data availability. Transmodeler is generally more powerful, but it will also incur greater costs, particularly since every consultant would need to acquire its own copy of the software.

This Technical Summary pertains to Report 2017-10, “Framework and Guidelines for the Development of a Twin Cities Mesoscopic DTA Model,” published April 2017.

Bicycling, Pedestrian, Research

New manual helps agencies count bike, pedestrian traffic

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As part of an ongoing effort to institutionalize bicycle and pedestrian counting in Minnesota, MnDOT has published a new manual designed to help city, county, state, and other transportation practitioners in their counting efforts.

The Bicycle and Pedestrian Data Collection Manual, developed by University of Minnesota researchers and SRF Consulting Group, provides guidance and methods for collecting bicycle and pedestrian traffic data in Minnesota. The manual is an introductory guide to nonmotorized traffic monitoring designed to help local jurisdictions, nonprofit organizations, and consultants design their own programs.Bicycle and Pedestrian Data Collection Manual

Topics covered in the manual include general traffic-monitoring principles, bicycle and pedestrian data collection sensors, how to perform counts using several types of technologies, data management and analysis, and next steps for nonmotorized traffic monitoring in Minnesota. Several case studies illustrate how bicycle and pedestrian traffic data can be used to support transportation planning and engineering.

The manual was completed as part of the third in a series of MnDOT-funded projects related to the Minnesota Bicycle and Pedestrian Counting Initiative, a collaborative effort launched by MnDOT in 2011 to encourage nonmotorized traffic monitoring across the state. U of M researchers, led by professor Greg Lindsey at the Humphrey School of Public Affairs, have been key partners in the initiative since its inception.

In addition to the manual, U of M researchers have published a final report outlining their work with MnDOT on this project. Key accomplishments include:

  • A new statewide bicycle and pedestrian traffic-monitoring network with 25 permanent monitoring locations
  • A district-based portable counting equipment loan program to support MnDOT districts and local jurisdictions interested in nonmotorized traffic monitoring
  • Minnesota’s first Bicycle and Pedestrian Annual Traffic Monitoring Report
  • A MnDOT website for reporting annual and short-duration counts that allows local planners and engineers to download data for analysis
  • Provisions added to MnDOT equipment vendor agreements that enable local governments to purchase bicycle and monitoring equipment
  • Annual training programs for bicycle and pedestrian monitoring
  • Provisions in the Statewide Bicycle System Plan and Minnesota Walks that call for bicycle and pedestrian traffic monitoring and creation of performance measures based on counts

“This is an excellent resource that steps through all aspects of managing a count program, and I think it will be very helpful to other states and organizations that want to implement their own programs,” says Lisa Austin, MnDOT bicycle and pedestrian planning coordinator. “Since Minnesota is a leader in counting bicycle and pedestrian traffic, it also fulfills what I think is an obligation to share our story with others.”

Bicycling, Pedestrian, Policy and Planning

Bike, pedestrian counting efforts engage local agencies statewide

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Across Minnesota, local agencies need better information about where and how many people are biking and walking to make decisions about infrastructure investments, understand safety risks, and even plan active living initiatives.

To help provide agencies with bicycle and pedestrian traffic data, U of M researchers have been working with MnDOT on the Minnesota Bicycle and Pedestrian Counting Initiative since 2010. The initiative is a collaborative, statewide effort to support bike and pedestrian traffic monitoring by local, regional, and state organizations.

Recently, the project team completed an implementation study—the second of three MnDOT-funded projects related to the initiative—specifically designed to engage local agencies. The goal was to demonstrate the feasibility of using both permanent and portable sensors to collect bicycle and pedestrian traffic data in several Minnesota cities, suburbs, and small towns.

“If we want to institutionalize counting and monitoring across the state, local agencies need to know it’s not something that’s only important for large cities like Minneapolis,” says principal investigator Greg Lindsey, professor at the Humphrey School of Public Affairs and current MnDOT scholar-in-residence. “We have to be on the ground in these places, illustrating that it’s relevant to the decisions they’re making.”

To that end, the team installed commercially available sensors—including inductive loops, passive infrared, pneumatic tubes, and radio beams—to collect traffic counts in several Minnesota cities. Overall findings indicate that all of the sensors produced reasonably accurate measurements—and that participating agencies found value in the collected data.

Findings and case studies from the study have already been incorporated into the draft Bicycle and Pedestrian Data Collection Manual, a new MnDOT guidance document being used in statewide training workshops. Also as a result of the study, MnDOT plans to include commitments to bike and pedestrian traffic monitoring in its forthcoming statewide bicycle and pedestrian plans. In addition, MnDOT is investing in a network of permanent traffic monitoring sites around the state as well as in portable equipment that will be available to local agencies.

Read the full article in the September issue of Catalyst.