The University of Minnesota (UMN) has been developing a system that uses a smartphone application to warn drivers of high-risk curves and inform them of a safe speed for navigating the bend.
Lane-departure crashes on curves make up a significant portion of fatal crashes on rural roads in the state of Minnesota. As an example of their high risk, curves make up only 19% of the total mileage of the paved St Louis County highway system, yet these bends account for 47% of all severe road departure crashes.
In a project that was funded by the Minnesota Department of Transportation (MnDOT) and the Minnesota Local Road Research Board, researchers at UMN developed a method of achieving dynamic curve warnings while avoiding costly infrastructure-based solutions.
The project team 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.
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.
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. 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.
“To improve safety, solutions are needed to help drivers identify upcoming curves. Traditionally there are two ways to do this: with either static signage or with dynamic warning signs,” explained project lead Brian Davis, a research fellow in the UMN’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.
“Our in-vehicle dynamic curve warning system was well-liked and trusted by the trial participants. We saw an 8-10% decrease in curve speed when participants were using the system.”