A car traveling along a rural road stops at an intersection with a divided highway. The driver waits for a gap in traffic on the highway, then moves forward into the intersection to merge with highway traffic. But the driver has made a dangerous miscalculation, and the car is struck by an oncoming vehicle that closed the gap too quickly.
This scenario plays out every day on rural roads throughout the United States, often with fatal results. Recent research has shown that gap acceptance problems, rather than issues such as stop sign violations, are the key factor contributing to crashes at unsignalized rural through-stop intersections.
But a groundbreaking system now being evaluated at an intersection in rural Goodhue County, Minn., could reduce the number of such crashes by giving drivers reliable, accurate information about approaching traffic. The system, developed by researchers from the ITS Institute’s IV Lab and HumanFIRST Program in cooperation with the Minnesota Department of Transportation, uses multiple sensors and advanced computer algorithms to track vehicles moving along a rural divided highway. This information is used to warn drivers stopped on a secondary rural road when gaps in highway traffic are too small to merge or cross safely. The Cooperative Intersection Collision Avoidance System (CICAS)-Stop Sign Assist (SSA) system uses an active LED icon-based sign that switches to an alert or warning as needed depending on the gaps to the left or right.
The field test, scheduled to last three years, will follow two tracks. The first track will focus on how individual drivers respond to the sign by using instrumentation installed in the vehicles of 30 drivers who regularly pass through this intersection. This will allow the research team to do a microscopic analysis of the data. The second track will consist of continuous data collection for all traffic passing though the intersection, which will facilitate a macroscopic analysis. Collected data will be analyzed throughout the test to determine whether measures of system performance, such as gap rejection behavior, are a valid measure of safety benefits.
As part of the test, the research team will determine how driver gap decision making and subsequent behaviors may change over time as a result of learning, familiarity, or satisfaction with the CICAS-SSA system. The test will facilitate the analysis of driver responses in relation to the system’s sign modes and also enable researchers to determine whether the CICAS-SSA system improves the gap acceptance of drivers. If drivers learn better behavior, crash rates should drop for all intersections, not merely those at which the CICAS-SSA system is deployed.
Learn more about Rural Unsignalized Intersections on the project's research page.