Tag Archives: work zone safety

Using Smartphones to Deliver Effective In-Vehicle Work Zone Messages

Under simulated conditions, drivers were not distracted by controlled work zone-related messages delivered through smartphones. In fact, driving performance improved. Researchers also learned that the location of the smartphone did not affect the driver if the message included an auditory component.

“The main goal was to determine whether in-vehicle warnings conveyed through smartphones would be distracting to the driver. We found that wasn’t the case,” said Ken Johnson, Work Zone, Pavement Marking and Traffic Devices Engineer, MnDOT Office of Traffic, Safety and Technology.

“We learned that drivers had a lower mental workload when they experienced the in-vehicle messages. It really didn’t matter what modality we used. Half the messages were auditory only, and half were auditory paired with visual,” said Nichole Morris, Director, University of Minnesota HumanFIRST Laboratory.

What Was the Need?

Highway work zones require drivers to reduce speed and be aware of work crews, lane closures, traffic backups, construction equipment and other potential hazards on the roadway.

Transportation departments have long employed stationary warning signs, sometimes supplemented by portable changeable message signs (PCMSs), to alert drivers to upcoming construction projects. However, some previous studies have indicated that stationary warning signs are not always effective. In addition, PCMSs are costly and may be difficult to deploy in the field.

Smartphone technology offers an opportunity to deliver accurate and early in-vehicle warnings about road construction miles ahead. Digital messages could alert drivers about upcoming work zone conditions and improve safety for drivers and workers in the field.

But receiving in-vehicle messages about work zone conditions could distract drivers from safely operating their vehicles. MnDOT needed to study the advantages and disadvantages of using smart-phones to deliver in-vehicle work zone messages.

What Was Our Goal?

The primary goal of this project was to determine whether smartphones have the potential to safely deliver effective and accurate messages to drivers about upcoming road construction on Minnesota highways.

What Did We Do?

A 7-inch LCD screen
A smartphone was replicated through installation of an LCD screen positioned inside the driving simulator.

The research team developed and conducted an online survey that focused on Minnesota drivers’ perceptions of work zone safety and on their attitudes toward using smartphones and potentially receiving in-vehicle messages regarding work zone conditions.

Data from the surveys was used by the HumanFIRST Laboratory at the University of Minnesota to develop a driving simulation study designed to determine whether in-vehicle messages sent by smartphones could promote safe driving in work zones. The study analyzed 48 drivers operating a driving simulator within two work zones to test reactions to in-vehicle messages as compared to messages displayed on an external PCMS system. Researchers collected data about each participant’s visual attention, driving performance, mental workload and opinions on smartphone technology.

Researchers also reviewed previous national studies and published works to identify environmental and driver behavior risk factors related to work zones.

What Did We Learn?

An analysis of the simulation results showed drivers were very responsive to receiving in-vehicle messages regarding work zones and roadway hazards. Messages presented through smartphones did not cause driver distractions. In fact, some drivers’ performance actually improved following delivery of audiovisual messages.

Drivers preferred to receive audio messages, and researchers learned that a synthesized female voice (like Apple’s Siri) resulted in greater awareness and acceptance from the driver than a more natural or prerecorded voice.

Survey findings showed that only 5 percent of participants use a dashboard mount for their smartphones, while the vast majority keep their phone in the cup holder, on the console, in a backpack or purse, or on the passenger seat. A few participants said they hold their smartphone while driving. Investigating the safety impact of this behavior paired with an in-vehicle messaging system, researchers found that the location of the smartphone within the simulator (on the dash or passenger seat) did not negatively impact driver safety or performance, providing the work zone message contained the auditory component.

In-vehicle messages required less cognitive effort from drivers, and drivers had greater recall of the hazard warning message versus stationary PCMS signage.

A significant number of survey participants, nearly 20 percent, provided unprompted feedback that it was the state’s responsibility to provide factual work zone messaging information and to ensure in-vehicle technology employed does not pose a distraction.

What’s Next?

MnDOT will need to continue research into the viability of smartphones as the way to deliver in-vehicle work zone messages. The simulation study provided the findings needed to advance the project to field testing, where drivers would respond to in-vehicle messages from smartphones on a test track or under real roadway conditions. Another potential topic to explore through further research is the viability of messages delivered through electronic interface or dashboard features offered on some newer vehicles.

MnDOT should identify the medium needed to deliver in-vehicle messages and use the prescribed syntax outlined by the study for communicating messages. Researchers noted the existing 511 service provided by MnDOT currently provides road, traffic, weather and other information. A study should be undertaken to determine whether the 511 or a third-party app would be most appropriate for a future statewide in-vehicle messaging program.


This post pertains to Report 2017-19, “In-Vehicle Work Zone Messages,” published June 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:

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.”

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.

Work-zone warnings could soon be delivered to your smartphone

Imagine that you’re driving to work as usual when your smartphone announces, “Caution, you are approaching an active work zone.” You slow down and soon spot orange barrels and highway workers on the road shoulder. Thanks to a new app being developed by University of Minnesota researchers, this scenario is on its way to becoming reality.

“Drivers often rely on signs along the roadway to be cautious and slow down as they approach a work zone. However, most work-zone crashes are caused by drivers not paying attention,” says Chen-Fu Liao, senior systems engineer at the U’s Minnesota Traffic Observatory. “That’s why we are working to design and test an in-vehicle work-zone alert system that announces additional messages through the driver’s smartphone or the vehicle’s infotainment system.”

As part of the project, sponsored by MnDOT, Liao and his team investigated the use of inexpensive Bluetooth low-energy (BLE) tags to provide in-vehicle warning messages. The BLE tags were programmed to trigger spoken messages in smartphones within range of the tags, which were placed on construction barrels or lampposts ahead of a work zone.

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The researchers also developed two applications for the project. First, they designed a smartphone app to trigger the audio-visual messages in vehicle-mounted smartphones entering the range of the BLE work-zone tags. A second app allows work-zone contractors to update messages associated with the BLE tags remotely, in real time, to provide information on current conditions such as workers on site, changes in traffic, or hazards in the environment.

Field tests proved the system works. “We found that while traveling at 70 miles per hour, our app is able to successfully detect a long-range BLE tag placed more than 400 feet away on a traffic barrel on the roadway shoulder,” Liao says. “We also confirmed the system works under a variety of conditions, including heavy traffic and inclement weather.”

“This was a proof of concept that showed that smartphones can receive Bluetooth signals at highway speeds and deliver messages to drivers,” says Ken Johnson, work-zone, pavement marking, and traffic devices engineer at MnDOT. “Future research will look into how we should implement and maintain a driver alert system.”

This future work includes using the results of a human factors study currently under way at the U’s HumanFIRST Laboratory to create recommendations for the in-vehicle message phrasing and structure. Then, researchers plan to conduct a pilot implementation with multiple participants to further evaluate the system’s effectiveness.

According to MnDOT, another phase of the project may investigate how to effectively maintain the BLE tag database. This phase could also investigate implementation options, such as how MnDOT can encourage drivers to download and use the app.

Work Zone Safety- How to Make Construction Sites Safer

If you have spent any time driving on Minnesota roads and highways lately, you know that road construction work zones are all over the place. They can contribute to traffic delays and require vigilance to ensure the safety of both drivers and workers.

MnDOT and the Minnesota Local Road Research Board (LRRB) are doing their best to make  work zones more efficient and safer for crew members and the traveling public alike.

Here’s a roundup of some of the great work zone safety projects under way or recently completed:

New – Temporary Traffic Control for Low Volume Roads

FlyerPicCity and county workers sometimes have trouble determining how to select the appropriate work zone for low traffic roads. The Minnesota Local Road Research Board (LRRB) recently published two supplemental guidebooks to help local agencies identify the appropriate work zone layout for low-volume urban and rural roadways based on the maintenance activity. The guides are intended to supplement MnDOT’s 2014 Temporary Traffic Control Zone Layouts Field Manual.The LRRB has also requested changes to the field manual  for low-volume roadways in a letter to the MN Committee on Uniform Traffic Control Devices.

Smart Work Zone Speed Notification 

MnDOT is testing a system on I-94 this summer that it hopes will reduce work zone crashes by raising driver awareness of upcoming congestion. Systems with the same purpose have been tested in rural work zones, but mostly applied to locations where backups were predictable.

The Smart Work Zone Speed Notification System will take a different approach, informing drivers of the speed ahead, as opposed to a variable speed limit system tested previously on I-94, which also detected congestion but provided advisory speeds to drivers. It is envisioned that the new system will have greater success in reducing rear-end crashes on large, urban freeway work zones.

The new system is being tested and evaluated on I-94, east of downtown St. Paul, during work to replace and repair the roadway.

NEW –  Speed Cameras in Work Zones

OLYMPUS DIGITAL CAMERAPolice enforcement and speed limits are the main method of reducing the speed of drivers in Minnesota work zones. While this practice is effective, reducing speeds by approximately 10 to 15 mph, it is not practical to staff every work zone with law enforcement. As an alternative, some states are using automated speed enforcement cameras in work zones.

Automated speed enforcement cameras have been shown to reduce speeds in work zones, but such research did not evaluate how the cameras impact driver attention.

This study explored driver awareness and found that automated speed enforcement cameras in work zones are not a source of driver distraction. It also revealed differences in work zone driving behavior: Older drivers were least able to follow another vehicle closely, while younger drivers were least likely to monitor their speed carefully.

NEW –  Reducing Work Zone Delay by Improving Traffic Models

2016-12 ImageAccurate estimation of delays caused by lane closures on highways is critical important to effectively manage traffic flows around work zones.

A recent study, completed in March 2016, improves methods for estimating reduced traffic capacity and diversion rates for highway work zones.

Researchers analyzed traffic patterns from past work zones in the Twin Cities metro area and were able to develop a tool that can estimate estimate traffic diversion for a given work zone.

The next step is an implementation project to test and streamline the software.

Work Zone Intrusion Reporting

TRS1506 ImageWork zone intrusions — when traveling vehicles enter the work space of a work zone — are a clear safety concern even if they do not result in an accident, and they may indicate locations where future accidents are likely.

MnDOT was interested in learning how other state DOTs collect work zone intrusion data, both the technology used for data collection and the specific information they collect.

This Transportation Research Synthesis (TRS), completed in June 2015, surveyed state DOTs and conducted follow-up interviews with states that collect work zone intrusion data. The survey found that the relatively small number of states that do collect intrusion data typically do so via paper or electronic form.

As a result of the TRS, a recently funded research project proposes to develop a simple method to track and gather information on work zone intrusions. The aim of this process will be to produce a reporting interface (in the same vein as the Crash Report Usability And Design Project for the Department of Public Safety) that gathers essential information without being onerous to work crews.

Auto Flaggers: Keeping Crews Safe, Saving Manpower

Training was provided to introduce MnDOT maintenance workers to Automatic Flagger Assistance devices, which can improve safety in work zones by allowing flaggers to provide traffic guidance without having to be in the flow of traffic.

Using a remote control, a single worker can easily operate two AFADs simultaneously, freeing up personnel to perform other tasks and speed up the completion of a road project, the pilot study found. MnDOT estimates that the resulting cost savings can cover an AFAD’s purchase costs within two years.

MnDOT has planned a project to determine whether it is feasible to use a self-propelled device to push or pull an AFAD so it can be used in moving operations such as patching potholes or cracks, which make up more than half of MnDOT’s flagging operations.

Using Smartphone and Bluetooth Technologies to Help the Visually Impaired Navigate Work Zones 

2014-12 ImageIn a study released in February 2014, researchers developed and tested a new system to provide audible messages to visually impaired pedestrians for navigating work zones.

The system uses Bluetooth beacons attached to work zone infrastructure that sends messages to a pedestrian’s smartphone app rather than the traditional method of beeping buttons that announce a message when pressed.

Technology to Alert Drivers to Work Zones

2012-26 ImageBy creating a tactile vibration and sound, rumble strips effectively alert distracted drivers to potential danger. However, they are not suitable for moving operations because repositioning them is too labor-intensive. MnDOT needed a method of alerting drivers about upcoming work zones that is more dynamic than
static signs but is portable and can be used in a moving work zone.

The Intelligent Drum Line system, developed in a 2012, could significantly improve work zone safety by relaying audible and visual warnings from traffic drums to speeding drivers as they approach. Further development is needed to ensure the system is cost-effective and portable to serve MnDOT’s needs.