Browsing by Subject "Gap acceptance"

Now showing 1 - 9 of 9
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    Driver Comprehension of Flashing Yellow Arrows
    (Minnesota Department of Transportation, 2023-12) Davis, Gary A.; Stern, Raphael; Duhn, Melissa; Gao, Jingru
    In 2009, the FHWA's Manual on Uniform Traffic Control Devices (MUTCD) introduced the flashing yellow arrow (FYA) traffic signal as an alternative to circular green (CG) to indicate permitted left turns. The FYA is arguably a more intuitive indication that left turns are permitted but not protected and, in addition, the FYA signal heads can support time-of-day changes between protective and permissive left -turn phasing. In 2019, a Research Needs Statement stated that "Research is needed to examine driver comprehension of flashing yellow arrows in different light arrangements and the role of signage." Our objective in this project was to assess drivers' understanding of FYA signal indications and to see if the presence or absence of "Left Turn Yield" signs affect gap acceptance. This was accomplished by conducting an online survey of drivers regarding their understanding of FYA signals and by carrying out a field study of drivers' gap acceptance at a set of Twin Cities intersections.
  • Thumbnail Image
    Item
    Field Study of Driver Behavior at Permitted Left-Turn Indications
    (Intelligent Transportation Systems Institute, Center for Transportation Studies, University of Minnesota, 2013-03) Davis, Gary A.; Mudgal, Abhisek
    A digital video camera was used to record left-turning vehicles and through vehicles at an urban intersection. A total of 39 left-turn events, with a total of 195 gap decisions, were identified and vehicle trajectories corresponding to those were extracted from the video and transformed into real coordinates using photogrammetry. Bayes estimates of each opposing vehicle’s distance, speed, and time-to-arrival were then computed from the trajectories and used as predictors in logit models of acceptance/rejection decisions. It was found, when models are penalized for the numbers of their parameters, that arrival time, the ratio of initial distance to initial speed, was best predictor. This contrasts with an earlier study that found distance clearly superior to arrival time. This may be due to the fact that in the current study, speeds and initial distances were substantially higher than in the earlier study.
  • Thumbnail Image
    Item
    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.
  • No Thumbnail Available
    Item
    A new design approach for High Occupancy Toll lanes
    (2013-07) Stanitsas, Panagiotis
    High Occupancy Toll (HOT) lanes are "oases" of free-flow conditions within congested freeways. Observations support the benefits of HOT and High Occupancy Vehicle (HOV) lanes implementation which in many cases can carry up to half of the people carried on the entire freeway. Developed operational strategies for the HOT lanes aim in controlling the demand so that a high level of service is provided to the users of the facility. A particularly important design feature of HOT lanes is the locations that vehicles can merge in or out; this feature is closely connected to the mobility and safety of the facility. This study paves the way for a systematic methodology that incorporates knowledge obtained from extensive periods of observations to the design of the Optimal Lane Changing Regions (OLCR) on forthcoming facilities. This methodology is applicable to HOT facilities that adopt a conservative design for their access zones by allowing interaction only at areas of high lane changing demand between exit ramps and entrance ramps to the freeway. Existing methodologies are based on engineering judgment or studies that take into consideration limited amount of observations. The proposed methodology was relied on a Monte Carlo sampling framework for revealing the advisory OLCR at various demand levels. Traffic flow is reconstructed for all the General Purpose Lanes (GPLs) of the segment of interest; headway sequences are constructed based on a calibrated Fundamental Diagram investigation for each GPL. A Gap Acceptance model was developed to shape the time increments that vehicles spend on each GPL. The final outcome of this methodology is advisory positions and lengths of merging areas on HOT facilities based on the simulated distance that vehicles travel between the entrance/exit ramp and the HOT lane. Another direction that this study aimed in making a contribution is access restriction on existing facilities in response to future increased demand levels; the goal is to preserve safety and mobility of the HOT facility. A quantity of major importance to the operation of buffer separated shared HOT lanes is the interaction between the HOT lane and its adjacent lane. The proposed methodology uses shockwave activity as surrogate for mobility and safety (shockwave length) to investigate the behavior of existing facilities for future demand levels. Specifically, shockwave length distributions were derived from a Monte Carlo sampling methodology taking advantage of a wave propagation model based on one-dimensional kinematic equations. After the proposed model was successfully tested for its ability to describe shockwave propagation on selected locations at present demand levels, an investigation of wave propagation at artificially increased density levels was conducted. The developed mechanism for achieving the increase in density was based on a scoring system that achieved the desired increase iteratively. Simulated shockwave length distributions were derived and the increased demand levels resulting in a flow breakdown on the HOT facility were identified. The outcome of this methodology can support the decision of engineers to restrict access to locations that reach their operational boundary.
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    A Simulator-Based Evaluation of Smart Infrastructure Concepts for Intersection Decision Support for Rural Thru-STOP Intersections
    (Minnesota Department of Transportation, 2007-08) Creaser, Janet; Rakauskas, Mick; Ward, Nic; Laberge, Jason
    This report describes the human factors basis for an intersection decision support (IDS) system intended to improve the safety of rural intersections in Minnesota's Interregional Corridors (IRCs). The purpose of the human factors effort is to understand the task of rural intersection negotiation, identify high-risk user groups, describe the human factors that contribute to intersection accidents, and determine what conceptual types of information to present in the IDS display to improve driver performance and safety. Consistent with the original infrastructure consortium proposal, this report emphasizes gaps, older drivers, and rural thru-STOP intersections (Donath & Shankwitz, 2001). This is because older drivers have a high accident risk at rural thru-STOP intersections and problems with gap detection, perception, and acceptance are contributing factors. A task analysis of rural thru-STOP negotiation was used to define the informational requirements for an IDS system for assisting with gap detection, perception and judgment. An abstraction hierarchy defined the operator (driver) constraints relevant to an infrastructure-based IDS system. Four design concepts were constructed and tested in a driving simulator with older (55+) and younger (20-40) drivers in day and night driving conditions. Two designs resulted in the largest mean gap acceptance across groups when compared to baseline. The two design concepts also were most favored by the majority of participants.
  • Thumbnail Image
    Item
    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.