Category Archives: Policy and Planning

New Office, Director to Foster ‘Culture of Innovation’

Katie Walker, Director of the Office of Research & Innovation

Katie Walker, formerly of Hennepin County, was recently named director of MnDOT’s new Office of Research & Innovation (formerly the Research Services & Library section), a role in which Walker will lean on her experience leading organizational change at Hennepin County.

During her 20-year tenure with Hennepin County, Walker held a variety of roles, including Southwest Light Rail Transit (LRT) Project Manager, Southwest LRT Community Works Program Director, and Public Works Policy and Planning Manager. Most recently, Walker headed strategic initiatives for the county’s Center of Innovation and Excellence, whose mission is to “create a culture where research, innovation and analysis bridges today with tomorrow to improve the quality of life for residents.”

“Fostering a culture of innovation at MnDOT will involve supporting creative thinking, new ideas and customer-focused solutions. We want to find ways to celebrate and share how staff are innovating on a daily basis – small changes that culminate to have an astounding impact. This not only supports our core values, but it equips us to better respond to a changing transportation environment,” said Walker, whose early career included stints as a planner for MnDOT, Dakota County and the Metropolitan Council.

Elevating Innovation throughout MnDOT

The Office of Research & Innovation – which formerly consisted of the MnDOT Library and research administration functions under the Office of Transportation System Management – was elevated to an office this year to better reflect the breadth of research occurring across the agency and play a stronger role in spurring innovation, both within and outside the state research program.

“There has been an emphasis on innovation at a federal level, both at the Federal Highway Administration (FHWA) and the American Association of State Highway and Transportation Officials (AASHTO). Reflecting this at the state level provides us the channel to better showcase the innovative work being done here at MnDOT,” said Jean Wallace, Assistant Division Director of Modal Planning & Program Management, who spearheaded a research strategic plan culminating in the organizational change.

The Office of Research & Innovation will remain a resource for MnDOT staff, as well as city and county engineers, kick-starting research and shepherding projects to completion. At any given time, program staff administer approximately 190 research projects, ranging from local initiatives to pooled fund projects with other states. Research program staff will also continue to work hand-in-hand with the MnDOT Library to provide fast, relevant, and cost-effective answers to the state’s transportation questions.

Strategic Plan Recommendations

MnDOT Research Program Strategic Plan

Other strategies recommended by the agency’s five-year Research Program Strategic Plan are also being implemented to improve how MnDOT conducts research and research implementation activities.

One recent outcome: Expanding the membership and responsibilities of the state research program’s steering committee, previously known as the Transportation Research and Innovation Group (TRIG). Historically charged with allocating state and federal transportation research funds, the steering committee will also now track and report on outcomes of research conducted across the agency, not just the projects it funds.  

Another change: MnDOT staff will be able to apply for research implementation funds any time throughout the year—instead of through an annual solicitation—to advance a new technology or practice in their work area, projects that are usually based on the findings of past research. This change aims to increase successful adoption of research findings within the department.

Study recommends strategies for reducing transportation disparities

Transportation contributes to many broad societal outcomes, such as employment, wealth, and health. Some Minnesotans, however, are underserved by current systems and face disparities and barriers in reaching their destinations. According to new research from the U of M, efforts to improve transportation equity need to focus on societal inequities—such as racial segregation and auto dependency—as well as the transportation barriers that affect specific communities and population groups.

“This study is an important early step in MnDOT’s Advancing Transportation Equity Initiative to understand how the transportation system, services, and decision-making processes help or hinder people in underserved and underrepresented communities in Minnesota,” says Hally Turner, planning program coordinator with MnDOT’s Office of Transportation System Management.

The underserved and underrepresented include low-income neighborhoods, communities of color, indigenous communities, rural residents, older adults, people with disabilities, women and youth, and people with limited car access.

Gina Baas, CTS associate director, engagement and education, was the principal investigator. The research team included co-investigator Yingling Fan (professor) and Leoma Van Dort (research assistant) of the Humphrey School of Public Affairs and co-investigator Andrew Guthrie (former Humphrey School research fellow, now assistant professor with the University of Memphis). MnDOT funded the study.

The researchers began by examining current research and practice in the field of transportation equity. They found that societal-level structural inequities cause specific population groups to face disproportionate transportation barriers.

“Some of these structural inequities, such as racialized spatial segregation in metropolitan areas and auto-dependent development patterns, are built into the very fabric of our communities,” Fan says. “The user-pay principle that governs the current transportation finance system is viewed as another inequity, as it does not take into account users’ ability to pay.”

Building on their review, the researchers then explored 24 programs from across the United States that aim to improve transportation equity. The result was structured, generalizable knowledge about the current state of the practice.

Stakeholder engagement was an integral component of the study. “We received key guidance from MnDOT, other public-sector agencies, and external community partners with expertise in addressing disparities and inequities,” Baas says. “We also engaged community members at a community event in Minneapolis to seek direct input from attendees about the day-to-day transportation challenges they face.”

Based on their findings, the research team developed recommendations for MnDOT and other transportation partners to consider in advancing transportation equity. The recommendations, categorized under six overarching themes (see below), address both societal inequities and the inequities of the transportation system itself. The report identifies which underserved and underrepresented populations are most likely to benefit from each recommendation, along with what modes of transportation each recommendation affects.

“The study lays a foundation for MnDOT to work with transportation partners to meaningfully reduce disparities,” Turner says.

The final report—Advancing Transportation Equity: Research and Practice—and a four-page policy brief are available on the MnDOT website.


Six themes for addressing transportation equity

  • Engagement processes. Design engagement processes that facilitate community leadership and the inclusive participation of traditionally underserved and underrepresented communities, where community members drive conversations around their transportation needs and strategies for implementing solutions.
  • Increased opportunities. Initiate programs and policies that increase access to social and economic opportunities, such as jobs, affordable housing, healthy food, education, health care, and recreation, particularly for underserved and underrepresented communities.
  • Transportation for sustainability and health. Create policies and programs that support active transportation and provide safe, smart, and affordable transportation alternatives that minimize automobile dependency to create healthier, more sustainable communities.
  • Equity spending. Integrate equity promotion as a standardized practice at the agency and program level, particularly in prioritizing spending across the system and distributing infrastructure projects.
  • Collaboration and coordination. Collaborate and coordinate across transportation and non-transportation agencies, institutions, and organizations—including academic institutions—to advance equity.
  • Evaluation metrics. Incorporate both quantitative and qualitative metrics for evaluating transportation programs and projects as well as their impacts on underserved and underrepresented populations

New Project: Extreme Flood Risks to Minnesota Bridges and Culverts

Extreme flooding is a threat to Minnesota’s transportation infrastructure and the safety and economic vitality of its communities. A spate of recent flooding events around the state has demonstrated this and heightened the level of concern. Furthermore, climate change — a factor not traditionally accounted for in the design of the state’s infrastructure — is projected to enhance precipitation and the threat of flooding in coming decades.

Given this, MnDOT is undertaking an effort to better predict the threat flooding poses to its bridges, large culverts and pipes, which may be increasingly called upon to convey higher, more frequent flood flows than they were designed for.

The state transportation research program recently launched a two-year extreme flood vulnerability analysis study, which will develop a methodology for characterizing the vulnerability of the state’s bridges, large culverts, and pipes to flooding.

The effort builds upon the previously completed Flash Flood Vulnerability and Adaptation Assessment Pilot Project (2014), which scored bridges, large culverts, and pipes in MnDOT Districts 1 and 6 for flood vulnerability, allowing detailed assessments of adaptation options for each of their facilities to be prioritized.

This new study, which will be conducted by WSP, aims to develop and test ways to enhance the vulnerability scoring techniques used in the previous study and ensure their applicability throughout the state. Researchers will not actually undertake the statewide assessment, but specify an approach that could be used for it. They will also explore how the outputs of the analysis can be incorporated into MnDOT’s asset management systems. The results of this work will be a clear path forward for MnDOT to use for prioritizing adaptation actions — a key step towards enhancing agency resilience and maintaining good fiscal stewardship.

Project scope

The primary intent of this study is to develop a methodology for characterizing the flood vulnerability of bridges, large culverts, and pipes statewide. As part of the development process, the methodology will be tested on a limited, but diverse, set of assets across the state. Following a successful proof of concept, recommendations will be made on how the outputs (i.e., the vulnerability scores) can be incorporated into the state’s asset management systems.

By determining which facilities are most vulnerable to flooding through the techniques developed on this project, MnDOT can prioritize where adaptation measures will make the biggest impact, ultimately decreasing asset life-cycle and road user costs. Without the development of assessment techniques, adaptation measures run the risk of being implemented in a more reactive and/or ad-hoc fashion, with less regard to where the biggest “bang for the buck” can be realized.

This project will produce several technical memorandums, and is expected to be completed in early 2021.

Roadmap created for rollout of unified OSOW permitting

The second phase is nearing completion for a project aimed at creating a Unified Permitting Process (UPP) for oversize/overweight (OSOW) vehicles in Minnesota. One outcome of this phase is a roadmap that will define steps for future phases, including statewide implementation.

Currently, haulers need to apply for OSOW permits with each individual roadway authority they will travel through. MnDOT, counties, townships, and cities all administer permits for their own roadways—so several different permit applications and processes can be required for a single haul.

“The streamlined permitting process is expected to increase efficiencies for the freight industry, which is good for our economy,” says Clark Moe, systems coordinator with MnDOT’s Operations Division, Office of Maintenance. “It will also enable more effective enforcement and help us preserve the quality of our road network.”

Through the UPP, agencies should have a better idea of what’s happening on their roads, says Rich Sanders, county engineer for Polk County. “Throughout the state, there are a lot of hauls we don’t even know about, let alone if they will use a restricted bridge or road.”

UPP Phases I and II

Phase I of the UPP project examined the feasibility of implementing a permitting platform. Completed in 2017, this phase included listening sessions across the state with the hauling industry, local agency engineers, law enforcement, state agencies, and MnDOT staff. Eighteen public and private entities collaborated to develop policies, processes, and plans for UPP technology. The final report concluded that a reference platform system for processing permit applications would be the best approach to explore.

Technical Schematic of a Reference Platform. The permitting platform will connect various software and data sources
The permitting platform will connect various software and data sources

Phase II was a proof-of-concept pilot project spanning St. Louis County, Polk County, the City of Duluth, and MnDOT Districts 1 and 2. The goal was to see if a permitting platform would work across jurisdictions connecting various permitting software and using multiple system processes. “The platform has to be usable in different ways and be able to channel payment back to MnDOT or a county or city,” Sanders says. “Phase II showed UPP could work.”

Phase II also underscored the complexity of the issues to come. “The vision is for haulers to enter their license data, and the required permit data would automatically populate the permit,” says Mitch Rasmussen, assistant commissioner with MnDOT State Aid. “But all kinds of software systems are now in use by local agencies, and MnDOT’s Office of Freight and Commercial Vehicle Operation is preparing to replace the two online systems it’s been using for decades. All the systems will need to talk to the unified platform. It will take time and money to build. The roadmap from Phase II can help us get there.”

Policy and fee differences are another challenge. To gather context and ideas, MnDOT recently completed a Transportation Research Synthesis to explore the practices of other state transportation agencies in setting, collecting, and distributing permit fees for heavy commercial OSOW vehicles (see related article). Another MnDOT study is under way to gather basic data about the permit fee policies of counties in Minnesota and throughout the country, including authority for the fees, cost range, and fee types.

When Polk County switched from a paper system to an electronic one, industry started applying for permits more consistently, Sanders says. With the paper system, five or six permit applications would be faxed in each year, and approval could take two days. But with its online system, the county received 201 applications between January 1 and October 26, 2018. “Approval might take us 30 seconds,” he notes.

UPP work to date has been funded by MnDOT and the Minnesota Local Road Research Board. Others involved include the Federal Highway Administration, state agencies (Minnesota Department of Public Safety, Driver and Vehicle Services, Minnesota State Patrol, Minnesota IT Services Geospatial Information Office), associations (Minnesota Association of Townships, Minnesota County Engineers Association, Associated General Contractors of America), private businesses (ProWest, SRF Consulting, Midstate Reclamation & Trucking, Tiller Corporation), and educational institutions (Upper Great Plains Transportation Institute, NDSU; Alexandria Technical & Community College). UPP Phases I & II were a unique collaborative public-private partnership to resolve a long-standing problem.

Next phases and final outcome

Moving forward, Phase III will begin development of the unified system using real data from multiple road authorities and databases in MnDOT Districts 1 and 2. Phase IV will take the platform beyond Districts 1 and 2 and roll out the system for testing statewide. Estimated completion is two to three years.

“Under current plans for the unified system, Minnesota road authorities will continue to set their own fees and may be able to connect their existing software, although some interoperable adaptations will be needed,” Moe says. “The new permitting process will focus on education for haulers, permitting agencies, and the public, as well as engineering decisions by agencies. This, in turn, will lead to increased enforcement effectiveness to help preserve road quality while boosting the economy.”

“Many decisions are still on tap,” Rasmussen adds. “There’s no decision yet of who’s going to own it and manage it, for example, or what fees might be recommended. There are a million moving parts, and many agencies and interests are involved. But we’re taking big strides toward our central goal: putting the right load on the right road, the right way, right away.”

This article by Pam Snopl originally appeared in the December issue of the Minnesota LTAP Technology Exchange newsletter.

New measure allows comparison between bridge and pavement conditions

Transportation planners lack a method to directly compare bridge and road conditions. In a new MnDOT-funded study, University of Minnesota researchers have proposed a Percent Remaining Service Interval (PRSI) measure that can uniformly assess the condition of bridges and pavements, enabling planners to make the most efficient use of preservation and improvement funding.

A nighttime view of workers and heavy equipment at a road construction site
Planners would like a condition measure similar to RSL that could be used to compare and prioritize needs for highway and bridge construction.

“Both the MnDOT Bridge Office and the Materials and Road Research Office have very good management systems in place,” says Mihai Marasteanu, a professor in the Department of Civil, Environmental, and Geo- Engineering (CEGE) and the study’s principal investigator. “There is a good potential to develop a new common metric that both offices could use.”

What Did We Do?

To begin developing this new measure, researchers conducted a literature review of current methods used in asset management and life-cycle cost analysis. The review of bridge research focused on performance measures and life expectancy assessment methods, while the study of pavement literature concentrated on performance measures as well as on the use of road service life measures.

Next, the research team, which included civil engineering bridge professor Arturo Schultz, surveyed both bridge management staff and pavement management staff from state transportation agencies. Team members then analyzed the asset management practices of MnDOT’s Office of Bridges and Structures and Office of Materials and Road Research to identify methods for assessing service lives and rehabilitation needs and to highlight the similarities and differences in approaches.

Based on the findings from the survey and analysis, researchers suggested the new method of PRSI that would serve both pavement and bridge needs and offered guidelines for the next steps in developing and implementing a unified PRSI procedure.

“Ultimately, funds for guardrail repairs are drawn from the same purse that pays to fill a pothole or repair a deck joint,” Marasteanu says. “With PRSI, planners could target average values across systems to optimize life-cycle costs and pursue an even distribution of PRSI values to make planning consistent from year to year.”

What’s Next?

In the next phase of the project, researchers will work with the pavement office to identify relevant data for calculating PRSI for pavements. “In addition, we plan to identify the time and costs required to reach the evenly distributed configuration of PRSIs necessary for planning consistency, assess how preservation activities impact funding efficiency, and calculate recommended metrics for asset sustainability,” Marasteanu says.

This article originally appeared in the Center for Transportation Studies’ Catalyst Newsletter, October 2018. The full report, published July 2018, can be accessed at “Remaining Service Life Asset Measure, Phase I,” .

 

 

Implementation of Research Strategic Plan Underway

Coverpage of Research Services Strategic PlanTo help guide the state’s future transportation research investments, the Minnesota Department of Transportation recently completed a five-year comprehensive strategic plan that looks at streamlining the research governance structure at MnDOT and developing a clearinghouse of information about the agency’s research portfolio to improve decision-making.

MnDOT Research Services, which administers the bulk of the state’s transportation research projects, recently completed a visioning session with agency stakeholders as the first step in implementing the recommendations of the strategic plan, which include:

  • Establishing agency-wide research strategic priorities
  • Tracking all of MnDOT’s research expenditures, including those performed outside Research Services
  • Tracking research investment levels to measure return on investment
  • Reporting on the outcomes of research projects beyond their life cycle
  • Identifying the value and impact of research at a topic and program level

In addition to the approximately 175 state, local and multi-state transportation research projects administered and tracked by MnDOT Research Services, several MnDOT specialty offices also invest in their own research to support or guide their work.

New Project: Development of Pavement Condition Forecasting for Web-based Asset Management for County Governments

Many counties have incomplete roadway inventories, but lack asset management programs, which are often cost-prohibitive and require advanced technical training and staff to maintain. The Upper Great Plains Transportation Institute at North Dakota State University (NDSU), has developed a low-cost asset inventory program called the Geographic Roadway Inventory Tool (GRIT). The program, which is currently available to North Dakota counties, will be offered to all Minnesota counties following further development and testing by the Minnesota Local Road Research Board.

Background

NDSU created the asset inventory program as the first step for asset management to allow local roadway managers to document and understand their existing infrastructure using the latest mobile technology and Geographic Information System technology.

The goal of the research study is to expand the program to include roadway forecasting based on the American Association of State and Highway Transportation Officials(AASHTO) 93 model with inventory, pavement condition and traffic forecasting data.

Existing input data from GRIT, such as pavement thickness, roadway structural information and construction planning information, will be spatially combined with current Pathway pavement condition and traffic data from MnDOT to automatically forecast the future condition and age of roadways using the AASHTO 93 model. This forecasting model will then allow roadway managers to use this information with comprehensive GIS web maps to prioritize roadways in construction schedule or multi-year plans.

Geographic Roadway Inventory Tool

Objective

The additional information contained in the pavement forecast system will allow county roadway managers to prioritize projects that can benefit from lower cost pavement preservation activities and understand how long roadways can last before a high cost reconstruction must take place. The online GIS output maps will also enable the public to see what projects will be conducted on a year-to-year basis.

Project scope

The research team will work with Beltrami, Pope, Faribault, Pennington, and Becker counties and the city of Moorhead in Minnesota to research, develop, test and implement an additional forecasting function of the existing asset management program. This will be done using the AASHTO 93 empirical model to calculate a future pavement serviceability rating (PSR) based on the existing pavement structure and age, forecasted traffic and the latest pavement condition. While existing pavement structure and age information will come from data entered into the GRIT program by counties, processes and procedures will be researched and developed to automatically access pavement condition and traffic data from MnDOT and geospatially combine it with inventory data.

With pavement forecast information, county roadway managers will be able to better understand which roadways will deteriorate first and which will benefit from more effective, low-cost maintenance programs rather than full-depth reconstructions. The model will not forecast suggested future projects or project costs, but rather just output the future condition of the roadways on a yearly basis. The AASHTO model can be applied for both flexible and rigid pavement sections.

Watch for new developments on this project.  Other Minnesota research can be found at MnDOT.gov/research.

New Project-Quantifying the Impacts of Complete Streets: The Case of Richfield

Complete Streets is a transportation policy and design approach that requires streets to be planned, designed, operated, and maintained to enable safe, convenient and comfortable travel and access for users of all ages and abilities, regardless of their mode of transportation. A newly funded research project aims to demonstrate the economic and non-economic benefits of Complete Streets in the city of Richfield, which has been active in reconstructing several previously vehicle-oriented roads to allow for safe travel by those walking, cycling, driving automobiles, riding public transportation, or delivering goods.

By measuring the impacts of pedestrian- and bike-related improvements in Richfield, this Minnesota Local Road Research Board-funded study hopes to help guide future transportation investments for building sustainable and safe urban environments.

This analysis will include four closely related steps:

  • First, University of Minnesota researchers will select suitable improvement sites in Richfield to study and collect project information, including project maps, description of complete street features and GIS files at the parcel level before and after the project.
  • Identify economic and measurable non-economic benefits. The university will work with the City of Richfield to identify possible economic benefits (such as increased property value) and other measurable benefits (such as public health benefits associated with pedestrian or cycling activities) of the Complete Streets projects.
  • Estimate economic benefits, such as increased housing value or as additional business activities.
  • Lastly, researchers will quantify and monetize non-economic benefits, such as public health or environmental benefits related to pedestrian or cycling activities. Data about benefit indicators will be collected through survey or interview. These benefits will then be monetized using common value parameters identified from the literature.

New performance measures identify truck delays and bottlenecks

A new freight transportation study takes the next step in lessening traffic bottlenecks by pinpointing location and time of recurrent delays.

Freight transportation provides significant contribution to our nation’s economy. Reliable and accessible freight network enables business in the Twin Cities to be more competitive in the Upper Midwest region. Accurate and reliable freight data on freight activity is essential for freight planning, forecasting and decision making on infrastructure investment.

Researchers used detailed and specific data sets as tools to investigate freight truck mobility, reliability and extent of congestion delays on Twin Cities metropolitan area corridors. Precise locations and times of recurrent delays will help to mitigate future traffic bottlenecks.

“This research provided tools and metrics with new levels of precision concerning truck congestion. The results will allow us to take the next steps toward future investment in addressing freight bottlenecks,” said Andrew Andrusko, Principal Transportation Planner, MnDOT Office of Freight and Commercial Vehicle Operations.

What Was the Need?

The corridors of the Twin Cities metropolitan area (TCMA) provide a freight transportation network that allows regional businesses to be competitive in the Upper Midwest. However, traffic volumes on many of these roadways are facing overcapacity during peak travel periods. Heavy truck traffic is only expected to increase, and delays will continue to disrupt freight schedules.

A 2013 study by MnDOT and the Metropolitan Council suggested the need to identify when and where truck congestion and bottlenecks developed in the TCMA. Previous research funded by MnDOT examined heavy truck movement along 38 Twin Cities freight corridors. Researchers created freight mobility and reliability measures, and worked to identify significant bottlenecks. Further research was needed to extract more precise data to better understand TCMA freight traffic congestion.

2018-15-p2-image
The top five congested AM and PM peak corridors in the TCMA are listed above with the delay hours for each period. The large delay hours arise from heavy truck volume and speeds far below base free-flow speeds.

What Was Our Goal?

The aim of this project was to combine data from the U.S. DOT National Performance Management Research Data Set (NPMRDS) with information from other sources to build on the previous study’s analyses of mobility, reliability and delay along key TCMA freight corridors. New performance measures would more clearly identify the extent of system impediments for freight vehicles during peak periods in selected corridors, allowing researchers to identify causes and recommend mitigation strategies.

What Did We Do?

Researchers worked with stakeholders to prioritize a list of TCMA freight corridors with NPMRDS data coverage. The NPMRDS includes travel time data from probe vehicles at five-minute intervals for all National Highway System facilities. The travel times are reported based upon Traffic Message Channel (TMC) segments with link lengths varying from less than 1 mile to several miles. Researchers worked with 24 months of NPMRDS data from the selected corridors.

Because of varying TMC segment lengths, researchers used geographic information system (GIS)–based data to georeference the NPMRDS data to relevant maps. Combining these with average travel time data from passenger and freight vehicles, researchers used their data analysis framework to generate measures of truck mobility, reliability and delay at the corridor level.

A truck mobility analysis of all the selected corridors was performed using the truck-to- ar travel time ratio (TTR) for each TMC segment of each five-minute interval computed in AM (6-10 a.m.), midday (10 a.m.-4 p.m.) and PM (4-8 p.m.) peak periods using the 24- month NPMRDS data. A TTR of 1 describes a truck and a car traveling a distance in the same amount of time. On average, trucks are known to travel 10 percent slower than cars on freeways: a TTR of 1.1. A truck traveling 20 percent slower would have a TTR of 1.2.

Reliability measures evaluated the truck travel time reliability. Researchers computed truck delay during rush hour on the GIS network by fusing truck volumes, posted speed limit and NPMRDS data.

Researchers computed a truck congestion measure by comparing truck travel time with the target travel time in each TMC segment, which provided a measure of delay (in lost hours) at the segment and corridor level.

What Did We Learn?

The truck mobility analysis revealed that roadways with intersections have a higher TTR. Trucks on U.S. and Interstate highways take about 10 percent longer to travel the same distance as cars: TTR 1.1. On state highways, the TTR reaches 1.2 and 1.4 in the AM and PM peak periods, respectively. On county roads, trucks slow considerably: midday TTR is 1.5 and spikes to 1.7 and 1.9 in the AM and PM peak periods. Intersections in a TMC segment and delays at signalized intersections could have caused the TTR increases.

All reliability measures indicated that truck travel time in the PM peak period is less reliable than in the AM peak period. Similar to the TTR measure, roadways with signalized or unsignalized intersections were less reliable for truck traffic than freeways.

Truck congestion and delay measures revealed that the top five TCMA corridors with significant congestion had an average delay of over 3,000 hours in the AM and PM peak periods, with the PM delays notably greater. Also, in the AM peak period, eight additional interchanges had average delays of over 300 hours per mile. In the PM peak period, nine interchanges and eight segments showed significant congestion.

The top six TMC noninterchange segments exhibiting recurring PM peak period delays on average weekdays had delays ranging from 495 hours to 570 hours per mile.

Insufficient capacity, increasing demand, roadway geometry and density of weaving points (on-and off-ramps) were considered key causes of delay among these six bottlenecks.

What’s Next?

NCHRP Research Report 854, Guide for Identifying, Classifying, Evaluating and Mitigating Truck Freight Bottlenecks, provides guidelines for identifying, classifying, evaluating and mitigating truck bottlenecks. Follow-up research by MnDOT could potentially leverage this project’s effort with the NCHRP guidelines to develop mitigation strategies.

This post pertains to Report 2018-15, “Measure of Truck Delay and Reliability at the Corridor Level, published April 2018.

 

Traffic Tubes Still Provide More Accurate Counts Than GPS Smartphones

Collecting traffic volume information from smartphone data, navigation systems and other GPS-based consumer and mobile technologies is not yet ready for use by MnDOT. However, the emerging technology offers useful information on driving origins and destinations for traffic monitors and planners.

“We’re on the cusp of using GPS technology to get traffic data from more facilities. We’re not there today, but we’ve spurred the industry to look at this opportunity,” said Gene Hicks, Director, MnDOT Traffic Forecasting and Analysis, who helped lead the research study on this topic.

MnDOT conducts traffic counts on its roadway network at regular intervals: every other year on state trunk highways, approximately every four years on city and county roadways, and every 12 years on low-volume roads. To make these traffic assessments, MnDOT currently stretches pneumatic tubes across traveled lanes and counts passing axles for up to 48 hours.

2017-49-p1-image
Using pneumatic road tubes to collect traffic data is an old and reliable practice, but installing them is time-consuming and puts workers in harm’s way.

“Using road tubes to collect traffic volume data is a proven method, but it’s an old practice and puts people in harm’s way. Smartphones may offer a useful alternative,” said Shawn Turner, Division Head, Texas Transportation Institute, who helped evaluate a beta version of traffic volume estimates derived from global positioning system (GPS)-based mobile devices.

What Was Our Goal?

With this project, researchers aimed to explore using smartphones and other GPS-based systems instead of pneumatic tubes to collect traffic volume data. The information collected was compared with actual volume counts from MnDOT traffic monitoring sites.

What Did We Do?

In May 2016 researchers began identifying data collection firms interested in participating in this research effort. These firms were developing products that gather, aggregate and analyze sufficient location data from GPS mobile devices to estimate traffic volumes. Researchers assessed and sorted packages from these firms to identify the best match for MnDOT’s needs.

Two firms that were initially interested withdrew from the project because their products were not ready for rigorous testing. The research team then developed an agreement to work with a third firm, StreetLight, to develop and evaluate traffic volume estimates from GPS-based devices.

Researchers and StreetLight worked together to develop and evaluate traffic volume data. Investigators provided MnDOT traffic count data to the vendor for calibration of its approach, and investigators suggested several ways to enhance StreetLight’s analytics.

2017-49-p2-image
Smartphones, navigation devices and other GPS-based consumer and commercial personal devices collect data that can be used to develop traffic volume estimators.

 

The vendor developed its proprietary approach, combining GPS-based navigation data with location-based service data. The firm normalized these two data sets with U.S. Census population projections, then calibrated and scaled samples with data from 69 MnDOT permanent ATR sites. StreetLight then estimated traffic volumes for MnDOT based on 7,837 short-duration count sites.

What Did We Learn?

On multiple-tube, high-volume roadways, MnDOT expects an accuracy of over 95 percent. The correlation between AADT tube-based data and StreetLight’s data was 79 percent without calibration and scaling, and 85 percent when scaled and calibrated. GPS-linked traffic volume estimations are approaching acceptable accuracy for MnDOT, but are not yet sufficiently accurate to replace tube counting for assessing AADT.

Estimation accuracy varies heavily with traffic volume levels. At high levels of traffic, larger sample sizes of mobile devices seem to drive more accurate assessments. At over 50,000 AADT, StreetLight estimates reached mean absolute percent error levels of 34 percent. At AADT levels below 20,000, the percent error rates ballooned. At all traffic levels, GPS-based data was measured at 61 percent mean absolute percent error.

Low-volume roads and frontage roads where multiple roadways converge had to be removed from count sites for estimating AADT. Overall, some of the GPS-based data fell within 10 to 20 percent absolute percent errors, which is acceptable, but other estimates fell well outside an acceptable range, and the highest errors occurred in low-volume roadway assessments.

What’s Next?

GPS-based data offers granular information that tube counts cannot, like average annual hourly volume estimates, and origin and destination data. With improvements to analytical processes for all data, GPS-based data may provide value outside of AADT estimates.

Currently, MnDOT is evaluating origin-destination data that StreetLight is providing for use in traffic studies and planning analyses. Current research by the University of Maryland and the National Renewable Energy Laboratory is gathering data with better error rates and will be extended in Colorado, Florida and Rhode Island. MnDOT expects volume estimation from GPS-based data will continue to improve and will likely be an acceptable alternative to tube counting in a few years.

This post pertains to Report 2017-49, “Using Mobile Device Samples to Estimate Traffic Volumes,” published December 2017.