Browsing by Subject "Unsignalized intersections"

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    The Design of a Minimal Sensor Configuration for a Cooperative Intersection Collision Avoidance System - Stop Sign Assist: CICAS-SSA Report #2
    (2010-08) Gorjestani, Alec; Menon, Arvind; Cheng, Pi-Ming; Shankwitz, Craig; Donath, Max
    The deployment of a Cooperative Intersection Collision Avoidance System – Stop Sign Assist (CICAS-SSA) can save lives by addressing the causal factor of crashes at rural thru-Stop intersection: drivers who stop on the minor leg of the intersection, improperly assess the gaps in the traffic on the major leg, proceed, and are then hit. The prototype CICAS-SSA system consisted of a network of sensors covering both the minor and the major legs of the intersection. Sensors on the minor road monitored the approach of vehicles and classified them based on their length and height. Sensors along the major road were arrayed to track vehicles (and the gaps between them) approaching the crossroads from 2000 feet away as a means to ensure that the tracking algorithm had sufficient time to “lock on” and track all approaching vehicles. Because cost is a primary concern for any highway safety application, the development of a “minimal sensor set” which would provide adequate safety performance for minimum cost was paramount to the success of the CICAS-SSA program. This report documents the development of this minimal sensor configuration.
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    Determination of the Alert and Warning Timing for the Cooperative Intersection Collision Avoidance System-Stop Sign Assist Using Macroscopic and Microscopic Data: CICAS-SSA Report #1
    (2010-08) Gorjestani, Alec; Menon, Arvind; Cheng, Pi-Ming; Shankwitz, Craig; Donath, Max
    Crashes at rural thru-stop intersections arise primarily from a driver attempting to cross or enter the mainline traffic stream after failing to recognize an unsafe gap condition. Because the primary cause of these crashes is not failure to stop, but failure to recognize an unsafe condition, the US DOT FHWA, MnDOT, and the University of Minnesota ITS Institute undertook the Cooperative Intersection Collision Avoidance System – Stop Sign Assist (CICAS-SSA) program. CICAS-SSA uses roadside radar sensors, a computer processor and algorithms to determine unsafe conditions, and an active LED icon based sign to provide timely alerts and warnings which are designed to reduce the frequency of crashes at rural expressway intersections. The focus of this report is the alert and warning timing used to provide a driver with assistance in recognizing and taking appropriate action when presented a gap which could be considered unsafe. The work presented herein uses both macroscopic data collected by roadside sensors and data acquisition equipment in Minnesota, Wisconsin, and North Carolina, and microscopic data collected using an instrumented vehicle and test subjects at the Minnesota Research Intersection, located at the intersection of US Hwy 52 and Goodhue County Road 9. Three tenets that are particularly germane to the determination of alert and warning timing for the CICAS-SSA system are: (1) the system does not help a driver choose a safe gap; it is designed to assist a driver with unsafe gap rejection, (2) it indicates when it is unsafe to proceed, not when it is safe to proceed, and (3) it must complement good decision making, and address those instances where poor decision making could lead to a crash.
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    Evaluation of the Effectiveness of Stop Lines in Increasing the Safety of Stop-Controlled Intersections
    (Minnesota Department of Transportation, 2020-07) Duhn, Melissa; Dirks, Peter; Loutfi, Andrew; Hourdos, John; Davis, Gary
    Stop lines are ubiquitous, but do they really impact intersection safety? Prior to this project, no long-term studies on intersection safety with stop lines had been completed. This project was developed with two parallel research efforts: a safety study and an observational study. The safety study was developed to address stop lines’ effects over the long term and used crash data from five cities’ stop-controlled intersections to perform regression and see if stop lines actually influenced safety. The observational study was developed to determine if stop lines have an effect on driver behavior at intersections and to look at where drivers were stopping. Video was collected at 16 different intersections before and after a stop line was painted. The safety study and observational study showed that stop lines did not have a significant impact on driver behavior or intersection safety, but other factors like speed limits and sight distance did. Implications for practice include carefully examining sight distance at the intended stopping point to ensure drivers have adequate sight distance in both directions. If sight distance is not adequate, moving the intended stop location or reconsidering whether the intersection should have signage -- stop or yield -- or be uncontrolled could yield better driver compliance and safety.
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    Guidelines for safer pedestrian crossings: Understanding the factors that positively influence vehicle yielding to pedestrians at unsignalized intersections
    (Minnesota Department of Transportation, 2023-06) Stern, Raphael; Li, Tianyi
    Many factors influence an individual driver's decision to yield or not yield to individual pedestrians attempting to cross the road at an unsignalized crossing. This study collects observational data from more than 3,300 crossing events at 18 intersections in Minnesota to further our understanding of what factors positively influence driver yielding. Using the collected data, a statistical analysis was conducted to identify features that most strongly correlate with driver yielding. Event specific features such as speed were found to greatly influence yielding, with vehicles traveling at a speed of greater than 25 mph significantly less likely to yield to pedestrians than vehicles traveling at speeds lower than 25 mph. Site-specific features such as the presence of signs indicating a crossing were also strongly correlated with driver yielding. The results provide indication of which features of unsignalized crossings correlate with higher driver yielding rates. These findings can be used to guide policy and design at sites where a high driver yielding rate is desirable.
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    Macroscopic Review of Driver Gap Acceptance and Rejection Behavior at Rural Thru-Stop Intersections in the US - Data Collection Results in Eight States: CICAS-SSA Report #3
    (2010-08) Gorjestani, Alec; Menon, Arvind; Cheng, Pi-Ming; Newstrom, Bryan; Shankwitz, Craig; Donath, Max
    Crashes at rural thru-stop intersections arise primarily from a driver attempting to cross or enter the mainline traffic stream after failing to recognize an unsafe gap condition. Because the primary cause of these crashes is not failure to stop, but failure to recognize an unsafe condition, the US DOT FHWA, MnDOT, and the University of Minnesota ITS Institute undertook the CICAS-SSA program. CICAS-SSA uses roadside radar sensors, a computer processor and algorithms to determine unsafe conditions, and an active LED icon based sign to provide timely alerts and warnings which are designed to reduce the frequency of crashes at rural expressway intersections. These rural, thru-stop crashes are problems in many states. In conjunction with the CICAS-SSA program, MnDOT and the University of Minnesota led a nine-state (CA, GA, IA, MI, MN, NC, NH, NV, and WI) pooledfund study whereby driver behavior data at rural thru-stop intersections was collected by the Minnesota Mobile Intersection Surveillance System (MMISS). The ultimate goal of the pooled fund study and the analysis of that data described here, was to identify whether drivers in different regions of the county exhibit different gap acceptance/rejection behavior, and if different driver behaviors are identified, determine whether they are different enough to inhibit the deployment of a common CICAS-SSA design throughout the US. The analysis of the data indicated that the system can indeed be deployed nationally.
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    Multi-city study of an engineering and outreach program to increase driver yielding at signalized and unsignalized crosswalks
    (Minnesota Department of Transportation, 2023-03) Morris, Nichole L.; Craig, Curtis M.; Drahos, Bradley; Tian, Disi; Van Houten, Ron; Mabry, Marshall; Kessler, William
    Pedestrian deaths are at a 30-year high nationally, accounting for 16% of total deaths in 2018 and far exceeding the previous decade of 12%, a trend mirrored in Minnesota. Previous research found an increase in local and citywide yielding at unsignalized crosswalks following an engineering and high-visibility enforcement program in Saint Paul, Minnesota. This study examined a modified engineering-focused (i.e., without enforcement) program expanded to both unsignalized and signalized intersections across the Twin Cities. The six-month study found modest improvements in yielding from baseline to treatment end (48.1% to 65.5% in Saint Paul and 19.8% to 38.8% in Minneapolis) at unsignalized engineering treatment sites but no improvements at generalization sites. No significant improvements in left- or right-turning yielding by drivers in Saint Paul were found at treated signalized intersections, but given that yielding was significantly worse at generalization sites over time, there may be some evidence that treatments mitigated performance declines among Saint Paul drivers during the study period. Yielding improvements at signalized treatment sites were more pronounced for only right-turning drivers in Minneapolis, but generalization sites showed no improvement or even worsened over time. Overall, study results suggested no shift in driving culture in either city, as found with the previous study using police enforcement, but found some evidence of local, site-specific changes in driver yielding behavior at treatment locations.
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    Sign Comprehension, Considering Rotation and Location, Using Random Gap Simulation for a Cooperative Intersection Collision Avoidance System – Stop Sign Assist: CICAS-SSA Report #4
    (2010-08) Creaser, Janet; Manser, Michael; Rakauskas, Michael; Donath, Max
    Crashes at rural thru-stop intersections arise primarily from a driver attempting to cross or enter the mainline traffic stream after failing to recognize an unsafe gap condition. Because the primary cause of these crashes is not failure to stop, but failure to recognize an unsafe condition, the US DOT FHWA, MnDOT, and the University of Minnesota ITS Institute undertook the CICAS-SSA program. CICAS-SSA uses roadside radar sensors, a computer processor and algorithms to determine unsafe conditions, and an active LED icon based sign to provide timely alerts and warnings which are designed to reduce the frequency of crashes at rural expressway intersections. The primary goal of this portion of the overall effort was to evaluate several candidate CICAS-SSA concepts in order to identify a single sign that may provide the greatest utility in terms of driver performance and usability at a real-world rural intersection. A secondary goal of the work was to determine the ideal physical characteristics (i.e., location and rotation of a sign relative to drivers) of the candidate CICAS-SSA at a test intersection to maximize comprehension (and subsequent use) of the sign. This report summarizes the results of the work.
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    Validation Study – On-Road Evaluation of the Cooperative Intersection Collision Avoidance System – Stop Sign Assist Sign: CICAS-SSA Report #5
    (2010-08) Rakauskas, Michael; Creaser, Janet; Manser, Michael; Graving, Justin; Donath, Max
    The CICAS-SSA sign is a roadside driver support system that is intended to improve gap rejection at rural stopcontrolled intersections. The CICAS-SSA system tracks vehicle locations on a major roadway and then displays a message to a driver on the minor road via an active LED icon-based sign. The basis of this sign is a “Divided Highway” sign that is commonly presented in traffic environments. Overlaid on the roadways of the sign are yellow or red icons that represent approaching vehicles that are at a distance at which the driver on the minor road should proceed with caution or at a distance that is considered unsafe to enter the intersection. Previous research conducted in a driving simulation environment indicated potentially beneficial changes in driver decision-making relative to approaching vehicle gap sizes and indicated that drivers perceive the system as being both useful and satisfying. While simulation-based evaluations provide a wealth of useful information, their ability to replicate the full array of behavioral, cognitive, and perceptual elements of a driving environment do have some limitations. It is because of these limitations that it is useful to confirm simulation-based findings in a real-world environment. The primary goal of the current work was to evaluate the candidate CICAS-SSA sign in a real-world setting to confirm previously identified benefits and identify any unintended consequences of sign usage. This goal was accomplished through a validation field test performed at the intersection of US Highway 52 and County Road 9 in Southern Minnesota. The findings of the work are summarized in this report.