New Project: Creating a Tool to Estimate Bridge Construction Time and Costs

MnDOT recently executed a contract with WSB & Associates Inc. to begin work on a research project titled “Bridge Construction Time and Costs.”

The research project will help the State of Minnesota’s Bridge Office develop a guidance document and a tool for bridge construction time estimation to be used by MnDOT District project managers and construction staff. The tool will provide a range of production rates based on specific design criteria, being more concise based on the level of information available and will aid in evaluating the potential benefit for accelerated bridge construction (ABC) techniques.

“This research will enable District project managers, who may not have bridge knowledge or background, to complete project planning and scoping more effectively,” said Paul Johns of MnDOT’s Office of Construction and Innovative Contracting.

Mike Rief of WSB & Associates will serve as the project’s principal investigator. Johns will serve as technical liaison.

According to the initial work plan, the project is scheduled to be completed by early March 2018, and WSB & Associates will complete the following tasks:

  1. Conduct an existing practices literature review of current departments of transportation processes around the United States for bridge time and cost estimation.
  2. Review and compile actual case study bridge construction production rates and cost data for major bridge components from state-provided diaries, schedules and bridge plans.
  3. Evaluate and select the best software format and style for a bridge construction time estimation tool. Load state case study production rate data into estimation tool and run validation using bridges currently under construction.
  4. Produce a research report summarizing the literature review on best practices. Produce a user guide for bridge time estimation tool and training presentation.
  5. An optional task, if the budget allows, will include the development of a cost estimating tool. Cost estimation data would be gathered from the literature review and case study analysis during the development of bridge construction time estimation tool for efficiency.

Using SMART-Signal Data to Predict Red Light Running at Intersections

This project developed a methodology using traffic data collected by the SMART-Signal system to identify intersections prone to red light running and, therefore, serious crashes. This methodology could help MnDOT prioritize intersections for safety improvements.

“The essence of this project was to develop a toolbox that traffic engineers can use to determine an intersection’s safety performance,” said Henry Liu, Research Professor, University of Michigan Transportation Research Institute.

Liu served as the study’s principal investigator.

“This research provides a way to classify intersections that have a higher potential for red light running,” Mick Rakauskas, Former Research Fellow, HumanFIRST Program, University of Minnesota

What Was the Need?

Engineers traditionally measure an intersection’s safety using the number of crashes that actually occur there. However, collisions are rare and somewhat random events, and it can take a long time to collect enough data to accurately assess a single location’s safety.

Traffic conflicts—“close calls” in which one or both drivers must brake, swerve or take some other evasive action to avoid a crash—happen much more often than collisions do. As a result, many research projects use traffic conflicts as an alternative measure of safety.

Red light running (RLR) is one of the most common and dangerous causes of traffic conflicts at signalized intersections. While not every RLR event leads to a collision, it is often the first step in a process that ends in one.

Additionally, crashes caused when drivers run red lights are typically right-angle crashes, which are frequently severe. About 45 percent of right-angle collisions result in injury compared to about 25 percent of other crash types. Reducing right-angle-crash frequency can therefore significantly improve overall road safety and reduce costs related to traffic collisions.

MnDOT’s Safety Group wanted to determine whether it was possible to objectively and automatically identify intersections where RLR events are most likely to occur. Developing a methodology to identify the most dangerous intersections would help MnDOT prioritize locations for safety improvements.

What Was Our Goal?

Several previous MnDOT research projects had developed the SMART-Signal system, an automatic system that collects data from traffic signal controllers at signalized intersections. MnDOT has installed the system at more than 100 intersections in the Twin Cities. This project sought to develop tools that use SMART-Signal data to evaluate safety performance at intersections.

What Did We Do?

flowchart
This flowchart shows the methodology for determining whether an RLR event will result in a crossing conflict.

Researchers analyzed SMART-Signal data collected at the intersection of Boone Avenue and Trunk Highway 55 (TH 55) in Golden Valley between December 2008 and September 2009. This intersection is equipped with both stop-bar detectors and advance detectors located about 400 feet upstream of the intersection. Researchers used stop-bar-actuation data and details about traffic signal phases to identify RLR events at the intersection.

However, since most intersections are equipped only with advance detectors, this method cannot be used to measure RLR events at all intersections. As an alternative, re-searchers used vehicle-speed and traffic-volume data from the advance detectors, along with recorded traffic-signal-phase information from SMART-Signal, to identify potential RLR events. They compared these potential events to actual RLR events identified using stop-bar data and developed a formula to predict whether an RLR event would occur. This formula can be applied at intersections of major and minor roads that are not equipped with stop-bar detectors.

Researchers then used data from a minor road to develop a method that identified whether an RLR event would lead to a traffic conflict. In this method, an intersection is first divided into four conflict zones (two in each direction). When a vehicle from the main road enters the intersection, the method enables researchers to calculate when the vehicle enters and leaves each of the conflict zones it passes through. Then they determine whether a vehicle from the minor road is in the same conflict zone. Using this methodology, researchers estimated the number of daily traffic conflicts at other inter-sections on TH 55. These estimates were based on data collected in 2009 and between 2012 and 2015.

Finally, researchers developed a regression model to evaluate whether adding the number of predicted traffic conflicts to a more standard model that used average annual daily traffic (AADT) would correlate with the number of actual collisions at that site. They evaluated the model using data from seven four-legged intersections and two T-intersections on TH 13 and TH 55.

What Did We Learn?

The formula for predicting RLR events matched observations 83.12% of the time, based on more than 2,000 data points.

The number of daily crossing conflicts at TH 55 intersections ranged from 7.9 (at Glenwood Avenue in 2009) to 51.2 (at Winnetka Avenue in 2013).

While limited data were available for the regression model (as no site had more than four years of SMART-Signal data available, and there were only 11 crashes in total), the model suggests that estimated average traffic conflicts and minor-road AADT both contribute to accurate prediction of right-angle-crash frequency, while major-road AADT does not. Due to the limited data available, however, these conclusions should be considered preliminary.

What’s Next?

While there are currently no plans for follow-up studies, additional research efforts could include continuing to evaluate and improve the prediction model as more data are collected, and installing video cameras at intersections to validate the proposed methodologies.


This Technical Summary pertains to Report 2017-08, “Estimation of Crossing Conflict at Signalized Intersection Using High-Resolution Traffic Data,” published March 2017. 

AVL Technology Enables Smarter, More Efficient Mowing Operations

A pilot project was begun to study the use of AVL technology in mowing operations. Potential benefits include improved mowing efficiency, improved reporting and ease of supervision, reduced paperwork and reduced spread of noxious weeds.

“Using the data we get from the AVL project, we can estimate how long it will take to mow the entire system,” said Douglas Maki, Asset Management Engineer, MnDOT Metro District. “That way, we can plan far in advance of major holidays, when the most traffic comes through our system.”

“The AVL technology can be used to mark newly disruptive weed locations and anything else a mower operator might see, like potholes, damaged signs or guardrails, and excessive or dangerous debris in the field,” said Adrian Potter, Senior Associate, SRF Consulting Group, Inc.

Potter served as the project’s principal investigator.

What Was the Need?

MnDOT is responsible for mowing roadsides along 14,000 centerline miles of highways for environmental and safety reasons. This is an enormous and critical task, requiring efficient use of employee time and mowing equipment, and efforts to avoid the spreading of noxious weeds, which will lead to increased use of herbicides.

A promising technology that many departments of transportation (DOTs) have installed is automated vehicle location (AVL). AVL systems provide a precise geographic location for DOT-owned vehicles so that real-time data can be obtained on field operations. This technology has been used for snowplowing and other fleet vehicle operations. However, only a few DOTs have used it for mowing operations.

To determine if AVL technology should be used in its
mowing operations, MnDOT undertook a pilot project involving 30 of its mowers. The locations chosen were Metro District roadsides, as MnDOT had previously invested in creating a geographic information system map of noxious weeds on those roadsides.

What Was Our Goal?

The goals of the pilot project were to:

  • Generate protocols for hardware installation and software training.
  • Set up the system for communicating data from the mowers to internal MnDOT servers.
  • Develop accomplishment reports based on data collected by the AVL units.
  • Develop and provide initial training to operators and supervisors.
  • Optimize the mower routes used.

What Did We Do?

For the 2015 and 2016 mowing seasons, researchers fitted 30 Metro District tractors with AVL technology, sensors and communication equipment.

The first stage of the project focused on developing the software interface required for the AVL system. The application had to provide a view of the mower’s exact location so that the mower operator could avoid noxious weeds. Data would be collected through an in-vehicle controller unit and transferred to MnDOT for analysis via a Verizon AirCard system installed on each mower.

Mechanics installed metal racks within each of the 30 mowers to protect the Ameritrak AT-500 AVL hardware unit. A video screen was mounted on the top of the rack. A reporting system was developed for use by operators, supervisors and managers. Training sessions were scheduled at the start of each season and when new operators were hired.

Interior view of mower cab showing location of AVL unit.

What Did We Learn?

The project achieved its initial goals of developing protocols for hardware and software, creating electronic reporting and capturing real-time data.

The research team gained the following insights during the planning and field-testing stages of the project:

  • Substantial time is needed to adequately develop and test the AVL software and hardware.
  • Implementing the system also requires considerable time due to resource limitations, and after implementation, it takes multiple mowing seasons to quantify weed and herbicide reductions.
  • MnDOT mower operators and supervisors recognized the value of the AVL system in improving the efficient use of their time, eliminating the drafting of written reports, and giving MnDOT a more accurate record of acreage mowed.
  • Since the tractors operated at such slow speeds, the initial data captured were too imprecise to analyze. But with software adjustments, this issue was resolved.
  • Installation of the AVL unit could have an impact on the operation of the tractor because the additional electrical burden that the unit places on the tractor battery may require the tractor to be sent to the manufacturer for inspection.

What’s Next?

The initial success of the pilot project provided the basis for continued use of AVL technology in Metro District mowing operations during the 2017 season and possibly beyond. MnDOT is currently evaluating whether this project has provided enough data to expand AVL to other districts in the state. The investigators estimate that after full implementation, MnDOT could save $100,000 per year.

MnDOT may consider installing AVL technology in other agency equipment to optimize and monitor maintenance activities.


This Technical Summary pertains to Report 2017-11, “An Innovative Approach to Smarter Mowing, Utilizing Automated Vehicle Location to Enhance Mowing Operations,” published April 2017.

Additional materials:

Choosing Effective Speed Reduction Strategies for Roundabouts

Using survey results and prior research, this project developed a new resource to enable Minnesota local road engineers to select appropriate speed reduction measures for roundabouts. Further research is needed to determine the relative effectiveness of different measures alone and in combination.

“Although roundabouts are becoming common, single-vehicle crashes from drowsy, inattentive or unfamiliar drivers are still a concern, particularly in rural areas,” said Joe Gustafson, Traffic Engineer for Washington County. “This project provides an overview of existing speed reduction treatments that have been used in both roundabout and nonroundabout contexts, and a framework to properly evaluate the effectiveness of new treatments.”

“Rather than try to identify the right combination of treatments, the research was designed to give engineers a variety of options to consider for a given location,” said Susan Chrysler, Senior Research Scientist, Texas A&M Transportation Institute.

Gustafson served as the technical liaison for the study, and Chrysler was the principal investigator.

What Was the Need?

2017-14-p1-image

Roundabouts can provide a safer alternative to traditional intersection control devices like traffic signals and stop signs. Roundabouts have been proven to reduce crash severity by requiring drivers to decrease speed during the approach to the intersection. But failure to slow down sufficiently could result in a crash.

Signs and markings are key treatments used to communicate to drivers that they must slow down as they approach the roundabout. When navigated appropriately, roundabouts can eliminate or reduce the severity of crashes, reduce delays and reduce fuel consumption.

What Was Our Goal?

This project had two goals: to analyze existing research and conduct a survey of roundabout design and installation practitioners to determine best practices; and to develop a resource that engineers can use to identify appropriate speed reduction treatments for high-speed approaches to roundabouts.

What Did We Do?

Investigators surveyed transportation engineers from Minnesota and other states, along with technical consultants, to learn their experiences managing roundabouts with high-speed approaches. The survey addressed geometric design parameters and traffic control methods, changes in maintenance practices, crash history and speed reduction measures that were considered or eventually enacted.

Previous research on the subject was studied, including the Federal Highway Administration report Roundabouts: An Informational Guide and National Cooperative Highway Research Program Report 672: Roundabouts: An Informational Guide, Second Edition. Design manuals from four states were reviewed to provide a sample of the material avail-able to practitioners seeking guidance on design of high-speed roundabout approaches.

Based on their research, investigators provided information on the effectiveness of various treatments and on their installation and maintenance costs. They also developed a methodology for conducting a speed study to assist engineers in determining the most effective treatment for a given intersection. Treatments for alerting drivers that a round-about is ahead include traditional signs, pavement markings, illumination and other indicators, plus advanced devices like speed-activated, LED-enhanced warning signs.

What Did We Learn?

Each roundabout presents unique challenges. Local road engineers need to evaluate the characteristics of the intersection being considered (such as geometric design and adjoining land use) and the costs of installation and maintenance before recommending a specific treatment or combination of treatments.

Other findings include the following:

  • Speed reduction techniques found effective for horizontal curves, urban-rural transition zones and isolated rural intersections should be effective for rural roundabouts with high-speed approaches.
  • In rural locations, speed reduction treatments that have been used at railroad crossings, T-intersections and work zones may also be applicable to roundabouts.
  • Some unique treatments used internationally hold promise, but further study is needed before these treatments can be recommended for use in the United States.

What’s Next?

This study was the first phase of research. The findings provide the methodology to select, install and evaluate treatments at different locations. Further research is needed to accomplish the following:

  • Analyze the effectiveness of speed reduction treatments at different locations
  • Determine the impact of different combinations of treatments
  • Establish the comparative benefits of two or more treatments that fall within the same general cost and maintenance grouping
  • Analyze the impact of roundabout infrastructure (such as gateway treatments and illumination), various pavement markings and the long-term effects of specific signing treatments.

This Technical Summary pertains to the LRRB-produced Report 2017-14, “Strategies for Effective Roundabout Approach Speed Reduction,” published May 2017. 

Self-propelled auto-flagger keeps workers out of traffic

Working with a Minnesota manufacturer, researchers developed a moving automated flagger assistance device (AFAD) that signals traffic at work zones. The AFAD is operated remotely by a worker who can stand off the roadway out of traffic.

“Everybody who has used the mobile AFAD has liked it. We love our stationary AFAD unit. These units have really big stop-slow signs—they’re so visible,” said Jeremy Gjovik, Transportation Operations Supervisor, MnDOT District 3.

“The AFAD is a one-of-a-kind device. We were able to basically start from scratch and come up with a device that meets all the needs it was designed for,” said Edward Terhaar, Principal, Traffic Engineering, Wenck Associates, Inc.

Terhaar served as the principal investigator for the study.

What Was the Need?

According to data from the U.S. Bureau of Labor Statistics, 149 roadway workers were killed nationwide from 2003 to 2015 while flagging or directing traffic, and many near misses have been reported with the increase in distracted driving that has come with mobile device use.

In 2014, MnDOT trained over 60 state and district maintenance workers in the use of an automated flagger assistance device (AFAD). The AFAD has been embraced in Minnesota as a highly visible device that effectively directs traffic in stationary maintenance and construction projects while keeping flagging personnel off the road during operation.

The AFAD does not, however, suit moving operations (like pavement crack sealing) because the device requires towing. Engineers at MnDOT wanted to determine if the AFAD could be made into a mobile device that could be operated by a road crew near, but not on, the roadway.

What Was Our Goal?

MnDOT funded this research to develop a self-contained, self-propelled mobile AFAD for use on moving work zone roadway projects.

What Did We Do?

2017-09-p2-imageResearchers met with MnDOT engineers to identify the features that would be required in a moving AFAD. They determined that the device would have to be towable to a construction site with standard towing gear, operable remotely through wired or wireless controls, movable forward and in reverse, and able to use rechargeable onboard batteries.

The research team investigated existing self-propelled devices from the United States, Canada and Australia for moving wheeled objects, large and small, to see if they could be adapted to these needs. No suitable device was found.

After further consultation with the Technical Advisory Panel, researchers approached DJ Products of Little Falls, Minnesota, a company that designs and manufactures devices (including battery-operated devices) for moving trailers, dumpsters, shopping carts and aircraft.

Researchers met with DJ Products in February 2015, reviewed its products and agreed that DJ Products would develop a prototype vehicle on which the AFAD could be mounted. In August 2015, after evaluating and modifying designs, DJ Products hosted a demonstration of the prototype vehicle without the AFAD attached. The research team requested modifications, and in April 2016, the company presented a new self-propelled device with the AFAD attached.

What Did We Learn?

Initial field testing was delayed due to seasonal weather issues and device operating problems that required the replacement of components. In February 2017, a MnDOT operator tested the mobile AFAD on a crack-sealing project on State Highway 71 south of Sauk Centre.

The moving AFAD can be operated with a wired or wireless controller, as well as with controls on a handlebar mounted on the vehicle. Operators must use one remote for moving the wheeled unit, and the remote from the original AFAD for sign messaging. The new device moves forward and backward, can be towed with a standard hitch, and employs onboard batteries and a charger.

Setup and takedown require more effort than conventional flagging, but this effort is not considered cumbersome. The moving AFAD can be operated by one person standing 400 feet or more off the roadway, and the device is large enough to be easily seen and understood by road users.

The new device was used for only one hour initially. The sealing crew was outpacing the moving AFAD because the crack-sealing project entailed few repairs with greater distance between repair locations than is typical of such projects.

What’s Next?

The moving AFAD device can be used as is, and is still being tested by MnDOT. Further modifications will be requested, including enhancement of the battery-powered unit, as it currently requires a battery change to operate through an entire work shift.

Steering and controller design will likely be modified. Currently, the moving AFAD operates like a rear-wheel-drive vehicle and must be steered from its rear-wheel, traffic-facing axle, forcing the remote operator to guide it up the road as if backing up a boat trailer. MnDOT operators may ask that the device be redesigned to be steerable from the traffic-leading end of the vehicle, as if it were pulling the signage up the road, allowing for more intuitive control.

MnDOT personnel would also like to see the device’s controller integrated with the sign controller, eliminating the need for two controllers—one for moving, the other for operating the sign. Nevertheless, the device appears to be a promising option for mobile AFAD use by an operator who need not stand on the road to direct traffic.


This Technical Summary pertains to Report 2017-09, “Development of a Moving Automatic Flagger Assistance Device (AFAD) for Moving Work Zone Operations,” published March 2017. 


Previous research:

ATM Queue Warning Systems Can Reduce Freeway Crashes

ATM queue warning systems were developed and deployed on two freeways to alert motorists to queuing conditions ahead that could lead to rear-end crashes. At one test site, the prototype system substantially reduced crashes and near-crashes. At the other site, it reduced speed variances.

“The big lesson learned was that the detection method had to function quickly and display a message that was timely and accurate. This gains the trust and confidence of the motoring public,” said Brian Kary, Freeway Operations Engineer, MnDOT Metro District.

“Deploying the product of this research was not difficult. The challenge came in closing the gap to alert the drivers to slow down,” said John Hourdos, Director, Minnesota Traffic Observatory, University of Minnesota.

Kary served as the technical liaison for the study, and Hourdos was the principal investigator.

What Was the Need?

To reduce congestion and improve safety, MnDOT has deployed active traffic management (ATM) technology on two highways in the Twin Cities freeway network. The ATM system incorporates intelligent lane control signals (ILCS) placed over selected lanes at half-mile increments to warn motorists of incidents or hazards ahead. With advance warning, drivers can slow down and possibly avoid crashes.

The deployed system, however, does not specifically target the prevention of rear-end collisions, which are the most frequent type of crashes on freeways. Research has shown that rear-end collisions tend to occur during extended lines of stop-and-go traffic and at end-of-queue locations. Overhead, real-time electronic messages that warn of queuing conditions ahead can prepare motorists to reduce speed and avoid potential rear-end collisions. Such messages have the added benefit of improving mobil-ity since fewer crashes will improve traffic flow.

What Was Our Goal?

This project sought to develop and field-test two different prototypes for ATM queue warning systems. One prototype would address stop-and-go traffic and end-of-queue situations. The other would address shock waves, a crash-facilitating condition where there is a sudden change in traffic movement that causes a cascade of braking. The long-range goal of the project is to develop a unified ATM queue warning system that can be deployed at other locations within the freeway network.

What Did We Do?

Development of two prototype high-resolution ILCS warning systems began in 2014. The systems were then deployed on two high-traffic freeways in the Twin Cities: one on Interstate 35 West (I-35W) and the other on I-94. Both were still in operation in mid-2017.

The two locations have significantly different traffic conditions. On I-35W, congestion creates expanding queues that extend from the Trunk Highway 62 (TH 62) interchange to the 50th Street overpass. At the I-94 location, crashes are most likely to occur due to shock waves that can often quickly develop near the Portland Avenue overpass.

2017-20-p2-imageTo capture traffic data, researchers used either live video from closed-circuit-camera detector stations or data from existing in-pavement loop detectors. The ILCS units dis-played the message Slow Traffic Ahead, which would direct drivers to reduce speed due to the congested lanes ahead. Other messages, such as Prepare to Stop or Traffic Ahead 10 MPH, were considered but not tested during this initial study.

A server installed at the Minnesota Traffic Observatory at the University of Minnesota archived the time and location of each queue on I-94 and measured its duration and length. This provided the data needed to develop two algorithms that can be used to develop a rear-end-collision warning system that can be installed at freeway locations where similar queuing conditions exist.

What Did We Learn?

The data collected show that warning messages delivered by the ATM system can be effective in alerting drivers to queuing conditions. The ultimate benefit is a reduction in rear-end collisions in downstream locations on the freeway.

Data recorded at the I-35W location revealed that:

  • Messages delivered by the ILCS system helped drivers maintain a steady speed and eliminate stop-and-go travel.
  • The contents of warning messages should be crafted to have an impact on all motorists. Drivers responded differently to specific messages.
  • Queue warning systems can be made more effective through deployment of a real-time, lane-specific ILCS system and collection of high-resolution data.
  • Some drivers did not always heed the first queue warning message to decrease speed, but they did slow down further along the roadway.
  • There was no significant difference in impact between warning messages issued during the morning peak travel period and those issued during the evening peak.

In the first three months of queue warning system operation, the crash frequency re-corded at the I-94 test site was 9.34 crashes per vehicle miles traveled (VMT) and 51.8 near-crashes. This was a 22 percent decrease from the 11.9 crashes per VMT recorded at the site in 2013 monitoring data, and a 54 percent decrease from the 111.8 near-crashes recorded there in 2013.

The research showed that to prevent potential collisions, the ATM system had to deliver messages quickly and accurately to give drivers enough time to adjust their speeds. Also, the control algorithms developed in this project can provide the queue-estimation projections needed by MnDOT and other transportation departments to enhance the effectiveness of their ATM systems.

What’s Next?

While the deployment of the two queue warning system prototypes was a relatively cost-effective option, a longer trial period of two to three years is needed to ensure that the ATM system delivers sustainable benefits.


This Technical Summary pertains to Report 2017-20, “Development of a Queue Warning System Utilizing ATM Infrastructure System Development and Field Testing,” published June 2017. 

Gauging safety of heavy vehicles on older concrete bridges

Bridges built using prestressed concrete girders are among the most common in Minnesota and throughout the U.S. because of their good performance, lower initial material costs, and relatively low ongoing maintenance costs. However, the federal requirements for these bridges have changed considerably over the years. As a result, bridges built to older specifications may score poorly when subjected to new bridge rating standards even though they are actually in good condition.

“One area in which this discrepancy between ratings and reality can cause problems is determining safe legal load limits for bridges, which are used to decide whether larger trucks may cross the bridge with an overload permit,” says Catherine French, CSE Distinguished Professor in the Department of Civil, Environmental, and Geo- Engineering and the study’s principal investigator.

“Our goal was to evaluate whether the current guidelines regarding shear forces (which transfer the loads to the supports) may be overly conservative for these older concrete bridges that are in good condition.”

Sponsored by MnDOT, the study was conducted by a team of U of M researchers including Carol Shield (co-investigator) and Benjamin Dymond.

Researchers used a multipronged approach consisting of numerical modeling and tests in both the laboratory and the field. The numerical modeling was used to apply the results of the laboratory and field tests to a study examining the effects of key parameters on the distribution of shear in a bridge system. Parameters included span length, girder spacing and depth, deck thickness, and load position.

Results showed that the shear forces for some bridges are not as high as those predicted by distribution factors in the current specifications—at least partially explaining why some MnDOT bridges with low shear ratings show no signs of distress, French says. The researchers provided recommendations for more refined methods of evaluating prestressed concrete girder bridges that rate low for shear and developed a screening tool to identify which bridges that rate low for shear should be further analyzed.

“The results of this project will help us re-evaluate aging bridges in our inventory, to distinguish those that really do have shear problems from those that don’t, and make decisions about whether they need to be replaced or rehabilitated for extra capacity,” says Yihong Gao, bridge designer with MnDOT’s Office of Bridges and Structures.

Resources:

Reducing speeds to improve safety for work-zone flaggers

When drivers approach a roadway work zone at high speeds, they put the lives of work-zone flaggers at risk. To keep flaggers safe on the job, U of M researchers are looking for better ways to capture drivers’ attention—and compel them to slow down—as they approach flagger-controlled work zones.

Kathleen Harder, director of the Center for Design in Health, and John Hourdos, director of the Minnesota Traffic Observatory, identified and tested new work-zone warning elements to more effectively capture and sustain driver attention. The project was funded by MnDOT and the Minnesota Local Road Research Board.

The project began with a simulator study in which participants completed three drives, each featuring a work zone with different warning treatments. One condition was a traditional four-sign configuration currently used to warn drivers approaching work zones. The other two conditions featured a variety of new elements, including signage with new messaging such as  a “one-lane road ahead” sign with flashing LED lights, a dynamic speed warning sign equipped with a loud warning horn that sounded if drivers exceeded the speed limit, and portable rumble strips.

“Overall, we found that the new set of elements is more effective than the elements currently used to reduce driving speeds on the approach to a flagger-controlled work zone,” Harder says.

Although adding LED lights to the one-lane road sign had no significant effect on drivers’ speeds, findings indicated that the dynamic speed sign coupled with the horn was more effective than the dynamic sign alone.

To test these new elements under real-world conditions, the researchers conducted field tests evaluating two configurations in Minnesota work zones. The first configuration followed the minimum standards outlined in the Minnesota Manual on Uniform Traffic Control Devices. The second deployed signs employing new messaging and attention-getting devices, including a dynamic speed warning sign, horn, and rumble strips.

Findings showed that the combination of the dynamic speed warning sign and the horn successfully reduced the overall speed of vehicles approaching the work zone. The portable rumble strips did not cause any significant speed reduction, but this may have been related to their location downstream from the dynamic speed sign and horn.

“Our findings reveal that the new set of elements designed to capture driver attention—including new messaging, a dynamic speed trailer, and horn—had a significant influence on reducing driver speed,” Harder says. “The experimental layout practically eliminated high-speed outliers and successfully reduced the approach speed to the flag operator.”

Seven Pilot Projects to Change Transportation Practice in Minnesota

Roadside fencing that protects endangered turtles, a toolkit for identifying potentially acid-producing rock and a device that could save MnDOT $200 million a year in pavement damage are just a few of the advancements that MnDOT hopes to make in the near future, thanks to seven recently funded research implementation projects.

Each spring, the governing board for MnDOT’s research program funds initiatives that help put new technology or research advances into practice. This year’s picks aim to improve the environment, reporting of traffic signal data, notification of lane closures and the design and quality of pavements.

Here’s a brief look at the projects (full proposals here):

Protecting the Environment and Wildlife

  • To avoid the leaching of potentially acid-generating rock during excavation projects, MnDOT hopes to develop a GIS-based risk-screening tool that identifies areas where PAG rock might be encountered. Guidance will be developed for identifying and handling PAG rock.

Found in bedrock throughout the state – especially northern Minnesota, PAG minerals can release acid upon contact with air or water, a danger to aquatic and human life.

“Anytime we dig, there is the potential to expose this stuff,” said Jason Richter, chief geologist.

  • Reducing roadway access for small animals, including endangered turtles, is a priority for MnDOT and the Minnesota Department of Resources. MnDOT will analyze the effectiveness of different types of small animal exclusion fences tried across the state and develop a standard set of designs for future projects.
Improved Reporting of Traffic Signal Data
  • A centralized hub of traffic signal data could benefit future vehicle-to-infrastructure (V2I) applications and assist with the modeling of transportation project impacts. Methods and tools will be developed for a regional database of intersection control information that extracts data from MnDOT’s recently acquired Central Traffic Signal Control System and soon-to-be adopted Signal Performance Measure application.
Real-Time Notice of Lane Closures
  • In this pilot project, 20 MnDOT arrow board messages will be equipped with technology that automatically reports lane closures on 511 and highway message boards, providing more timely motorist notification.
Longer-Lasting Roads and Improved Quality Control
  • This summer, a new quality assurance device called the Rolling Density Meter will be deployed on several pavement projects, eliminating the need for destructive sample cores.
    “This is the ultimate in compaction control,” said Glenn Engstrom, Office of Materials and Road Research director. If contractors obtain the right level of density when paving asphalt roads, MnDOT could eliminate $200 million per year in premature road failure.
  • In 2018, MnDOT plans to require Intelligent Compaction (a pavement roller technology that reduces workmanship issues) on all significant asphalt projects. A vehicle-mounted mobile imaging device will be piloted that collects necessary supportive roadway alignment data, without the need for survey crews.
  • Upgrades to MnDOT’s pavement design software, MnPAVE, (incorporating recycled unbound and conventional base material properties) will help increase the service life of Minnesota roads.

New work-zone warning app featured on KARE 11

A new app that sends warning messages to drivers as they approach work zones was featured on KARE 11 News on Thursday. The app was developed by U of M researchers in a project sponsored by MnDOT.

The story aired as part of KARE 11’s #eyesUP campaign to end distracted driving.

The app works by pairing with Bluetooth low-energy tags placed in work zones, triggering audio warnings in smartphones that are within their range. This allows drivers to get a warning message without having to look down at their phones—or at warning devices such as changeable message signs outside their vehicles. And if a driver is being distracted by their phone, the app will interrupt whatever they are doing to provide a warning that a work zone is up ahead.

U of M researchers Chen-Fu Liao and Nichole Morris, who worked on the project, are interviewed in the story, along with Ken Johnson, work-zone, pavement marking, and traffic devices engineer at MnDOT.

Minnesota transportation research blog