Cities and counties need affordable pavement preservation treatments, but preservation strategies are often geared towards higher-volume roads. The Minnesota Local Road Research Board has developed new guidance on five lower-cost treatments that is more applicable to local agencies and can be used to preserve pavements based on the type and severity of pavement distress.Continue reading Pavement Preservation Techniques for Local Agencies
Managing a fleet of trucks, heavy equipment, and other vehicles challenges road agencies large and small. While large agencies like MnDOT use software and specialized administrators to manage fleet management systems electronically, city and county agencies often do not. For some small agencies, fleet management may fall to a shop mechanic or two.Continue reading Guidebook helps cities and counties choose tools for managing fleets
In a newly completed study, researchers found that stabilized full-depth reclamation has produced stronger roads for commercial loads in Minnesota, and the method shows promise for uses in rural agricultural areas. How much greater the strength gained with each stabilizing agent is better understood, though not conclusively.Continue reading Recycling Asphalt Pavement Offers Strong Alternative to New Aggregate Base
Several years of research have culminated in the publication of a culvert design manual that promotes the safe passage of fish and other aquatic organisms, as well as stream connectivity, throughout the state.
“Engineers designing culverts for Minnesota’s diverse ecological regions will benefit from this document, which offers sound guidance from many practicing experts about how to design culverts that allow aquatic organism passage and preserve stream integrity,” said Petra DeWall, former Bridge Waterway Engineer, Minnesota Department of Transportation (MnDOT).
What Was the Need?
Minnesota’s 140,000 miles of roads and approximately 92,000 miles of streams and rivers meet at tens of thousands of places. Culverts are a cost-effective solution to allow traffic to cross over smaller waterways. Historically, culverts have been designed with the safe passage of vehicles in mind. Recently, a state and national appeal for the safe passage of fish and other aquatic organisms, as well as for waterway integrity and connectivity, has influenced culvert design.
MnDOT has supported many research projects examining fish and aquatic organism passage (AOP) through culverts, and nationally, a number of published resources exist on appropriate design. Because of the variety of ecological regions in the state, the range of culvert geometries and many other factors, no single solution can accommodate AOP through culverts statewide. A comprehensive culvert design guide was needed to inform designers about solutions that can effectively facilitate the movement of fish and other aquatic organisms in Minnesota while maintaining healthy streams.
What Was Our Goal?
The objective of this project was to produce a comprehensive and accessible culvert design guide that could be used by Minnesota practitioners to design culverts for AOP and stream connectivity. The guide would provide the following benefits:
• More efficient culvert design and permitting process for AOP.
• A central definition of typical designs, which would improve contractors’ familiarity with designs and lower construction costs.
• Avoidance of designs that could be detrimental to the natural environment.
• Avoidance of designs likely to lead to roadway damage and need for repairs.
• Fishery improvement through increased stream connectivity.
What Did We Do?
To determine the scope of the guide, researchers worked with experts from the Minnesota Department of Natural Resources (DNR), the U.S. Forest Service and others with knowledge of civil engineering, AOP and stream geomorphology.
They then sought information for the guide from a wide range of authoritative resources. A literature search examined current and past research by the research team and others; guidance documents from federal agencies; guidance from other states; permit requirements from the DNR and other agencies; and databases of fish populations, stream attributes and culvert data. The literature search also sought to reveal gaps in knowledge where further research specific to Minnesota was needed.
Additionally, researchers surveyed a cross section of highway design engineers and managers from MnDOT, county and city agencies, resource agencies and engineering consultants to identify current design practices for AOP and stream connectivity, and the degree of their effectiveness.
What Did We Learn?
The project resulted in the Minnesota Guide for Stream Connectivity and Aquatic Organism Passage Through Culverts, a thorough guide for culvert designers, hydraulic engineers and others involved in culvert design and construction in Minnesota. Topics addressed in the guide include:
• The need for culvert designs that include AOP and stream connectivity, as well as the current regulatory context.
• An overview of culvert design, categories of design methods that incorporate AOP and waterway connectivity, and a list of best practices.
• Site characteristics, analysis and tools related to energy dissipation, hydraulic analysis for AOP and sediment transport.
• A design method selection chart, information on certain designs and references for further information.
• Further guidance about design issues such as multiple barrel and floodplain culverts, grade control, retrofits and other cost considerations.
The culvert design guide will be made available to users online. Future considerations for this project include an associated webinar and efforts to coordinate information presented in the guide with expectations and permitting requirements of MnDOT departments charged with culvert creation and implementation. Additional research is underway to assess culverts and fish passage with respect to storm vulnerability and future hydrologic scenarios.
This post pertains to the MnDOT and LRRB-produced Report 2019-02, “Minnesota Guide for Stream Connectivity and Aquatic Organism Passage Through Culverts,” published January 2019.
Researchers have developed an affordable camera-free curve and lane departure warning system that relies on consumer-level GPS, rather than sophisticated, expensive digital maps.
The technology uses cumulative driving trajectory data from GPS points detected every 100 milliseconds to predict driving path trajectories and compare these to mapped curves and lanes. With further development, the system can be used as an inexpensive smartphone app or retail device to warn drivers of lane drift and approaching curves.
“The goal of the project is to reduce lane departure crashes. We viewed this as a seed project and demonstrated that the system can be successful,” said Victor Lund, Traffic Engineer, St. Louis County.
What Was Our Goal?
The Minnesota Local Road Research Board sought research to develop a camera-free curve and lane departure warning system that uses consumer-level GPS capability without reliance on sophisticated, expensive digital maps.
What Was the Need?
Lane departures and run-off-road crashes cause more fatalities and serious injuries in Minnesota than any other accident type.
Many current warning technologies rely on cameras that identify lane position based on pavement markings. In inclement weather, stripes and pavement markings can be difficult or impossible to identify; markings also wear off over time, reducing visibility even in clear conditions. Camera-based lane departure warning systems are also expensive and generally restricted to newer luxury vehicles, making them inaccessible to the general driving public.
Though in-vehicle technology for the public usually falls outside the research interests of the Minnesota Department of Transportation and the Minnesota Local Road Research Board, the agencies have been funding development of lane departure warning technologies to improve driver safety. GPS technologies offer an intriguing path to consumer-level lane departure warning systems.
High-level GPS can be accurate to the centimeter level, but access is restricted and use is expensive. These systems also rely on accurate, lane-level roadway mapping, an elusive data set with high access costs.
What Did We Do?
Researchers began with a literature search of the uses of standard GPS receivers in lane departure and navigation. The research team then developed an algorithm for travel direction that uses standard GPS in a straight road lane departure system to determine driving trajectories at accuracy levels suited to safe driving needs.
Investigators adapted a publicly available digital mapping platform to the same algorithm to identify navigational points along curves and develop the curve lane departure warning system. The team enhanced standard safe distance methods to consider driver reaction time in determining when approach warnings should be issued.
Researchers then brought the two developmental stages of the system together with a warning system that identifies vehicle speed, curvature characteristics and safe speed limits, and calculates distance for driver response times to issue an audible warning to drivers on lane drift and a text warning of when and how much to reduce speed as the vehicle approaches a curve.
For project testing and demonstration, investigators programmed the algorithm into a device with a built-in GPS receiver, connected it to a laptop for messaging and conducted driving tests on Rice Lake Road and on Interstate 35 near Duluth.
“From a technical point of view, this approach works. We developed a warning system with standard GPS that everyone has in a phone or vehicle. This is a lifesaving technology in a sense,” said Imran Hayee, Professor, University of Minnesota Duluth Department of Electrical Engineering.
What Did We Learn?
Finding no research on development of consumer-grade GPS for lane departure purposes, the research team adapted previous work on the relative accuracy of GPS readings from a MnDOT study on wearable GPS for work zone safety.
Researchers adapted a consumer-level GPS device to acquire data at 10-hertz frequency, which yields a GPS position point of 2.7 meters if a vehicle is driven at 60 mph.
The system calculates lane trajectory from cumulative readings and detects turns or drift. The curve warning system plots trajectories and compares these with open-source digital maps with road-level (rather than lane-level) accuracy to anticipate curves.
In road testing, the system issued audio warnings for every one of the approximately 200 lane changes, including curves. For curve warnings, the system scanned for curves at least half a mile ahead and calculated the vehicle’s speed and the distance to a curve to issue a timely text warning of the curve ahead and an advisory speed limit. Additional messages were issued when the vehicle was on the curve and when the curve had ended.
False alarms—warnings issued when the vehicle was not departing its lane—occurred in 10 percent of the tests, usually on sharp curves. Further adjustment of the algorithm and additional testing reduced false alarms significantly as the system accumulated data over multiple uses of the same roadway.
Investigators filed a patent for the technology and will continue to develop the system. Further refinement of reference road direction information will improve accuracy and safety; the research team has developed a new project to employ vehicle-to-vehicle dedicated short-range communication technology to expand road direction reference data. The system will then need to be adapted for a consumer-level device or a smartphone app for use in any vehicle.
This post pertains to the LRRB-produced Report 2018-34, “Development and Demonstration of a Cost-Effective In-Vehicle Lane Departure and Advanced Curve Speed Warning System,” published December 2018.
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.
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.
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.
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.
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.
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.
Local agencies are increasingly looking at converting low-trafficked paved roads to gravel at the end of their life span to make budgets stretch. However, agencies have few resources to guide them in this process.
The Minnesota Local Road Research Board recently approved funding for a guidebook on effective practices for converting severely distressed paved roads to unpaved roads. The document will help engineers select roads for conversion, safely conduct conversions and communicate the rationale to the public. No such published document currently exists.
Montana State University researchers has been hired to develop the guidebook based on needs the research team previously identified in the National Cooperative Highway Research Program’s Synthesis 485, “Converting Paved Roads to Unpaved. The guidebook, anticipated to be published in late 2019, will include flowcharts that guide practitioners through decision-making processes. A companion webinar is also planned.
The guidebook will be divided into chapters, which will cover:
- Methods to determine if a road is a candidate for conversion and determine the existing road materials and condition.
- Methods to convert a road from paved to unpaved.
- Methods to assess the life-cycles cost of construction and maintenance of the unpaved road.
- Tools to effectively inform and communicate with the public
- Safety implications of converting a severely distressed paved road to an unpaved road.
While low- volume roads are typically identified as having an annual average daily traffic (AADT) of less than 400, roads that are appropriate candidates for conversion will typically have an AADT of less than 150.
These roads are often used by agricultural and extraction industries or to access homes and recreational areas. The type of road users, traffic patterns and vehicle types are all factors that need to be considered in the decision to unpave a road. Other factors include road condition, safety, agency maintenance and maintenance capabilities, as well as a life-cycle cost comparison of maintenance options (continued maintenance of the deteriorating road, rehabilitation of the paved road or conversion to an unpaved surface).
According to the research team, very limited information is available about converted roads, and what information is available often comes in the form of newspaper articles and anecdotal accounts of road conversions.
The document will serve as a formal and peer-reviewed information source. The use of the guide and acceptance of the practice of converting from paved to unpaved surfaces (unpaving) where warranted will provide a case for the acceptance of road conversions as another low-volume road management strategy.
The city of Shoreview, Minnesota was on the right track when it took the unusual step of paving a residential neighborhood with pervious concrete to help control stormwater and pollutant runoff into a nearby lake, according to a recently released seven-year performance study.
Typically used for parking lots and sidewalks, porous paving material allows stormwater to filter through the pavement and an aggregate base into the soil rather than run off the pavement and drain into storm sewers.
Shoreview bucked convention by using pervious concrete in a traffic application — low-volume, low-speed roads in the Woodbridge neighborhood near Lake Owasso. The city thought pervious pavement could help meet community sustainability goals and federal clean water regulations by reducing pollutants in waterways and groundwater while keeping water safely off driving surfaces.
Traditionally, pervious concrete hadn’t been used for roadways because engineers didn’t consider it strong enough for traffic (this and other projects have now demonstrated its application for low-volume roads like neighborhood streets). The impact on ride quality, tire-pavement noise and filtration was also not well understood, particularly in cold climates with freeze-thaw cycles like those in Minnesota.
Pervious concrete also presented a maintenance challenge: Organic debris, sand and other grit can clog the pavement’s pores. Periodic vacuuming is required to maintain the intended flow of water through the pavement. Concerned about how best to maintain the pavement and interested in tire-pavement noise levels and filtering performance, Shoreview, MnDOT and the Local Road Research Board monitored the Woodbridge roadways for seven years.
Installation and Evaluation
Shoreview replaced 9,000-square -feet of asphalt roads with 7 inches of pervious concrete over 18 inches of coarse aggregate base; near the lake, highly drainable sand served as the base. About twice each year for five years, researchers tested sound absorption, water infiltration and ride quality one day after the pavement had been vacuumed. In 2015, they repeated these tests without vacuuming the day before.
The pervious pavement performed well in filtering stormwater. By 2012, at least 1.3 acre-feet of water had filtered through the pavement and ground, and by 2015, nearly 2 acre-feet of water had filtered through the surface—all of which would otherwise have run directly into Lake Owasso.
Water infiltration and sound absorption rates were higher than traditional concrete, although rates declined over time because organic material continued to clog pavement pores despite vacuuming twice a year.
Initial construction of the pervious concrete streets and stormwater filtration system was slightly more costly than construction of comparable asphalt pavement with culverts. Life-cycle costs, including projections of maintenance costs over 15 years, however, showed somewhat lower costs for pervious pavement. While the pervious concrete pavement may require diamond grinding after 10 years, monthly vacuuming could make this unnecessary. Asphalt pavement would typically require a mill-and-overlay at year 15, and culverts would require periodic cleaning.
Additional benefits of the pervious pavement system that were not included in cost calculations—but were clearly significant—included complying with the federal Clean Water Act, recharging groundwater and avoiding direct pollution of Lake Owasso. Shoreview’s investment in pervious concrete has paid off economically and environmentally.
For additional information about this line of research, see these resources:
- Seven-year study final report
- Technical summary of preliminary study of pervious concrete
- Related ongoing study: Permeable Pavement for Road Salt Reduction
Researchers have developed a tool to help Minnesota local agencies make cost-effective pavement marking decisions in their counties. The spreadsheet-based tool was developed as part of a recently completed research study by the Minnesota Local Road Research Board.
What Was the Need?
Minnesota has many miles of low-volume roads, most marked with yellow centerline and white edge lines. Applying and maintaining these markings is a significant financial investment for local agencies, which typically work within very constrained budgets. These agencies needed more information about the value and the initial and ongoing costs of typical 4-inch and enhanced 6-inch pavement markings on low-volume roadways. They also needed clarification and guidance for prioritizing pavement marking installation and maintenance that could work within their limited budgets.
What Was Our Goal?
The goal of this research was to develop a prioritization approach and a decision-making tool for using pavement markings on low-volume roads based on the benefits and costs of these markings. Local agencies could then use these resources to make cost-effective decisions about installing and maintaining pavement markings.
What Did We Do?
Researchers took a multistep approach to identifying critical pavement marking information and practices:
• Conducted a literature search of existing research on typical (4-inch) and enhanced (6-inch) pavement markings, focusing on the benefits (such as crash reduction and improved lane-keeping), costs and current maintenance practices.
• Surveyed Minnesota counties to learn about their current practices and management approaches for pavement markings.
• Reviewed existing County Road Safety Plan (CRSP) methodology to learn about research and data used to rank at-risk road segments and identify CRSP improvement strategies, specifically the range of pavement markings that CRSPs recommended.
Researchers were then able to develop a prioritization approach and a decision-making tool that incorporated both past research and local state of the practice. In addition to producing a final report describing task results, they developed a brochure explaining the approach, the tool and implementation steps.
“This innovative tool will help local agencies make pavement marking decisions under tight budget constraints, where the question is always how to best allot funds for competing needs. This tool clarifies the problems and helps prioritize the possible solutions,” said David Veneziano, LTAP Safety Circuit Rider, Iowa State University Institute for Transportation.
What Did We Learn?
The literature search revealed limited research addressing traditional pavement marking use and effectiveness on local roadways. Pavement markings produce safety benefits, including reduced crash rates, but showed no real effects on vehicle speed, indicating that pavement markings may not alter driver behavior. Only limited efforts were identified in the literature aimed at investigating the prioritization and management of pavement markings.
The survey of local Minnesota agencies revealed that most counties use centerline and/or edge lines, which may be the result of MnDOT State-Aid Operation Rules. Some counties mark all their roads; most use 4-inch latex paint or epoxy markings. Repainting schedules depend upon road age, marking condition and county budgets.
A review of Minnesota counties’ CRSPs showed they included pavement marking recommendations. The CRSPs recommended, on average, 109 miles of pavement markings in every county. Applying one linear foot of centerline costs about 5 cents; 100 miles of centerline cost $26,400. Because of the extent of these recommendations, researchers directly incorporated the methods and directives from the CRSPs into their prioritization approach and tool.
The spreadsheet tool produced through this project allows users to enter road site characteristics such as pavement condition, road width, the CRSP rating and traffic volume, as well as the age of extant markings, costs, durability and the potential for crash reduction. Pavement marking options include centerline and/or edge lines, high visibility markings and enhanced durability materials. The tool uses factor weights that assign a relative importance to each criterion for any potential marking approach compared to other alternatives. The result is a performance rating score for each marking alternative. Thus, the tool assists not only in identifying the physical aspects of a road segment, it also incorporates the agency’s preferences, priorities and budget through a priority-weighting feature that generates the cost or cost range for a marking project.
Recommendations for further research include conducting a follow-up survey of users
of the new spreadsheet tool to facilitate future modifications, creating databases of roadway characteristics to simplify agencies’ use of the tool, and performing additional research on the safety and other effects of pavement markings. Researchers also encouraged agencies to keep in mind a proposed national retroreflectivity rule for the Manual on Uniform Traffic Control Devices that could affect pavement marking practices on low-volume roads. This rule has not yet been finalized or implemented.
This post pertains to LRRB-produced Report 2018-21, “Investigating the Necessity and Prioritizing Pavement Markings on Low-Volume Roads,” published June 2018. The Pavement Marking Prioritization Tool can also be found on the project webpage on the LRRB website.