In a recent research project, MnDOT sought to validate a smartphone app designed to guide pedestrians who are blind or visually impaired through signalized and unsignalized intersections. The project succeeded in showing the app’s effectiveness in tests at six intersections in Stillwater, Minnesota.
This article was originally published in Catalyst, August 2020.
More than five years ago, U of M researchers studied a group of new teen drivers to gauge the effects of real-time, in-vehicle coaching with their innovative Teen Driver Support System (TDSS) smartphone application. Now, a follow-up study offers new understanding about the system’s long-term effectiveness in reducing risky driving behavior.
Researchers have developed a proof-of-concept curve speed warning system for use with mobile phones, a technology they hope car manufacturers might adopt for in-vehicle systems. The proof-of-concept system uses data from local road agencies on curve locations, speed limits and signage with geofencing to trigger cloud-based data alerts to road users driving faster than recommended speeds for curves.
Lane-departure crashes on curves make up a significant portion of fatal crashes on rural Minnesota roads. To improve safety, solutions are needed to help drivers identify upcoming curves and inform them of a safe speed for navigating the curve.
“Traditionally there are two ways to do this: with either static signage or with dynamic warning signs,” says Brian Davis, a research fellow in the U of M’s Department of Mechanical Engineering. “However, while signing curves can help, static signage is often disregarded by drivers, and it is not required for roads with low average daily traffic. Dynamic speed signs are very costly, which can be difficult to justify, especially for rural roads with low traffic volumes.”
In a recent project led by Davis on behalf of MnDOT and the Minnesota Local Road Research Board, researchers developed a method of achieving dynamic curve warnings while avoiding costly infrastructure-based solutions. To do so, they used in-vehicle technology to display dynamic curve-speed warnings to the driver based on the driver’s real-time behavior and position relative to the curve. The system uses a smartphone app located in the vehicle to provide the driver with visual and auditory warnings when approaching a potentially hazardous curve at an unsafe speed.
“Highway curves [make up] 19 percent of the total mileage of the paved St. Louis County highway system, yet these curves account for 47 percent of all severe road departure crashes,” says Victor Lund, traffic engineer with St. Louis County. “In-vehicle warnings will be a critical strategy to reduce these crashes.”
To begin their study, researchers designed and tested prototype visual and auditory warning designs to ensure they were non-distracting and effective. This portion of the study included decisions about the best way to visually display the warnings and how and when audio messages should be used. “To create the optimal user experience, we looked at everything from how to order the audio information and when the message should play to the best length for the warning message,” says Nichole Morris, director of the U’s HumanFIRST Lab and co-investigator of the study.
Next, a controlled field test was conducted to determine whether the system helped reduce curve speeds, pinpoint the best timing for the warnings in relation to the curves, and gather user feedback about the system’s usefulness and trustworthiness. The study was conducted with 24 drivers using the test track at the Minnesota Highway Safety and Research Center in St. Cloud, Minnesota. The selected course allowed drivers to get up to highway speeds and then travel through curves of different radii, enabling researchers to learn how sensitive drivers are to the position of the warnings.
Based on the study results, the system shows both feasibility and promise. “Our in-vehicle dynamic curve warning system was well-liked and trusted by the participants,” Davis says. “We saw an 8 to 10 percent decrease in curve speed when participants were using the system.”
The project was funded by MnDOT and the Minnesota Local Road Research Board.
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?
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.
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.
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.
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.
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.
Each year, approximately 17 percent of road construction work zone fatalities nationwide are pedestrians.
At special risk are the visually impaired, who rely on walking and public transportation to get around.
A major challenge for them is crossing the street — which is even more difficult if an intersection is torn up.
MnDOT has invested significant effort to accommodate pedestrians, particularly those with disabilities, in temporary traffic control situations. This includes requiring temporary curb ramps and alternative routes when a sidewalk is closed.
Researchers, funded by MnDOT, have now developed a cell phone application to guide blind pedestrians around a work-zone.
Building on previous work to provide geometric and signal timing information to visually impaired pedestrians at signalized intersections, the smartphone-based navigation system alerts users to upcoming work zones and describes how to navigate such intersections safely.
The smartphone application uses GPS and Bluetooth technologies to determine a user’s location. Once a work zone is detected, the smartphone vibrates and announces a corresponding audible message. The user can tap the smartphone to repeat the message, if needed.
The federal government strongly encourages states to provide either audible warnings or tactile maps at work zones where visually impaired pedestrians are expected to be impacted.
“The smartphone application is a step in that direction,” said MnDOT technical liaison Ken Johnson. “It’s a way to see if this type of way-finding device would work.”
Since smartphone use is still limited, the state is also interested in special equipment that could relay the audible warnings at affected work zones.
“However, smartphone use is increasing in the general population, as well as with persons with disabilities, and there will likely be a day when it will be rare to not have a smartphone and this tool could meet road agency needs,” Johnson said.
Before developing the smartphone application, researchers surveyed 10 visually impaired people about their experiences at work zones and what types of information would be helpful in bypass or routing instructions.
The University of Minnesota research team, led by Chen-Fu Liao, tested the smartphone application by attaching four Bluetooth beacons to light posts near a construction site in St. Paul.
Additional research is now needed to conduct experiments with visually impaired users and evaluate system reliability and usefulness.