Browsing by Subject "Traffic safety"

Now showing 1 - 20 of 31

Accident Prevention Based on Automatic Detection of Accident Prone Traffic Conditions: Phase I
(University of Minnesota Center for Transportation Studies, 2008-09) Hourdos, John; Garg, Vishnu; Michalopoulos, Panos
Growing concern over traffic safety as well as rising congestion costs have been recently redirecting research effort from the traditional crash detection and clearance reactive traffic management towards online, proactive crash prevention solutions. In this project such a solution, specifically for high crash areas, is explored by identifying the most relevant real time traffic metrics and incorporating them in a crash likelihood estimation model. Unlike earlier attempts, this one is based on a unique detection and surveillance infrastructure deployed on the freeway section experiencing the highest crash rate in the state of Minnesota. This state-of-the-art infrastructure allowed video recording of 110 live crashes, crash related traffic events, as well as contributing factors while simultaneously measuring traffic variables such as individual vehicle speeds and headways over each lane in several places inside the study area. This crash rich database was combined with visual observations and analyzed extensively to identify the most relevant real-time traffic measurements for detecting crash prone conditions and develop an online crash prone conditions model. This model successfully established a relationship between fast evolving real time traffic conditions and the likelihood of a crash. Testing was performed in real time during 10 days not previously used in the model development, under varying weather and traffic conditions.
Developing an Intelligent Decision Support System for the Proactive Implementation of Traffic Safety Strategies
(Intelligent Transportation Systems Institute, Center for Transportation Studies, 2013-03) Chen, Hongyi; Chen, Fang; Anderson, Chris
The growing number of traffic safety strategies, including the Intelligent Transportation Systems (ITS) and lowcost proactive safety improvement (LCPSI), call for an integrated approach to optimize resource allocation systematically and proactively. While most of the currently used standard methods such as the six-step method that identify and eliminate hazardous locations serve their purpose well, they represent a reactive approach that seeks improvement after crashes happen. In this project, a decision support system with Geographic Information System (GIS) interface is developed to proactively optimize the resource allocation of traffic safety improvement strategies. With its optimization function, the decision support system is able to suggest a systematically optimized implementation plan together with the associated cost once the concerned areas and possible countermeasures are selected. It proactively improves the overall traffic safety by implementing the most effective safety strategies that meet the budget to decrease the total number of crashes to the maximum degree. The GIS interface of the decision support system enables the users to select concerned areas directly from the map and calculates certain inputs automatically from parameters related to the geometric design and traffic control features. An associated database is also designed to support the system so that as more data are input into the system, the calibration factors and crash modification functions used to calculate the expected number of crashes will be continuously updated and refined.
Developing and Validating a Model of Left-Turn Crashes to Support Safer Design and Operations
(Center for Transportation Studies, University of Minnesota, 2018-09) Davis, Gary; Gao, Jingru; Mudgal, Abhisek
This report documents work done to advance the state of art in crash simulation. This includes: (1) A field study to collect data on drivers’ left-turn gap acceptance and turning times, and development of statistical models that can be incorporated into a crash simulation model; (2) The use of Markov Chain Monte Carlo computational tools to quantify uncertainty in planar impact reconstruction of two-vehicle crashes; (3) A method for combing the results from planar impact reconstruction with event data recorder pre-crash data to estimate descriptive features of actual left-turn crashes. This is applied to several left-turn crashes from the National Highway Traffic Safety Administration’s NASS/CDS database; (4) A left-turn crash simulation model incorporating the above results. Initial model checking is performed using estimates from the reconstructed NASS/CDS cases as well as results from a previous study on left-turn crash risk. Also described is a method for simulating crash modification effects without having to first simulate crashes as rare outcomes in very large numbers of gap acceptances.
Developing Driving Support Systems to Mitigate Behavioral Risk Patterns Among Teen Drivers
(University of Minnesota Center for Transportation Studies, 2007-08) Brovold, Shawn; Ward, Nic; Donath, Max; Simon, Stephen
Based on statistics from the Centers for Disease Control and Prevention (2003), motor vehicle deaths are the leading cause of teenage fatalities. A possible approach to mitigate the incidence of teenage driver crashes and fatalities is through the use of in-vehicle technology. The design and development of a first-generation prototype Teen Driver Support System (TDSS) to explore the feasibility and opportunities of such technology has been completed. The TDSS system includes technology designed to address several primary contributing factors associated with the majority of teen fatal crashes: speeding, seatbelt use, driver inexperience, and alcohol use. This has been implemented using a combination of what researchers call forcing, feedback, and/or reporting functions. Forcing functions take the form of ignition interlocks to enforce seat belt compliance and sober driving. A feedback function provides real-time tutoring and warnings about illegal or unsafe speeds through auditory warnings. A reporting function records vehicle information for parents to review and supervise (and enforce) teen driver performance. A speed feedback and reporting component is used for driver compliance with safe travel speeds. The system correlates the location (using GPS) of the vehicle to a digital road map and the road's corresponding speed limit. A weather-based speed element incorporates current weather information that is used to warn a driver if the vehicle's speed is too high for current weather conditions. Similarly, speed warnings specific to curves are included to warn if speed is excessive for the prevailing geometry. With the prototype TDSS, the researchers developed a method of integrating a seat belt interlock that requires the driver's seat belt to be engaged before the vehicle will start. Seat belt use is continuously monitored during each trip, and lack of seat belt use is recorded for later review. An additional interlock for alcohol is reserved for teen drivers with preexisting alcohol-related convictions. Since alcohol interlock systems are commercially available, they can be demonstrated as an optional component of the TDSS. In anticipation of potential future applications, such as the enforcement of certain graduated driver licensing (GDL) requirements, the system includes a biometric fingerprint component, which uses a fingerprint sensor to identify the driver and parent so that the system can log the number of training hours spent behind the wheel.
Development and Evaluation of a Cellular Phone Based Teen Driver Support System
(University of Minnesota Center for Transportation Studies, 2009-08) Creaser, J.; Hoglund, R.; Manser, M.; Donath, M.
Motor vehicle crashes are the leading cause of death for teenagers with speeding, seat belt non-compliance, alcohol involvement, and distractions serving as the primary contributors to this unacceptably high crash rate. In an effort to mitigate this situation, a prototype teen driver support system (TDSS) has been designed and developed. This computer-based system provides real-time feedback to teens regarding speed limit violations and warns of upcoming speed zone changes. A unique feature of this system is that speed limit feedback is relative to the speed limit posted on the roadway on which the teen is driving. By informing teens of speeding behavior, it is hoped that this system will reduce teen crash rates. This project includes a description of the TDSS features and specifications for how the TDSS operates using the Smart Phone technology. A small usability study was completed as part of the project where teen drivers (aged 18-19) drove with and without the system. Overall, the pilot study demonstrated that the TDSS could operate effectively within a vehicle driven by a teen driver. Warnings and messages were presented to the drivers and corresponding text messages were sent when drivers failed to alter their behavior in relation to a warning. The performance data trended in the direction expected, with the TDSS encouraging lower speeds and less speeding overall. The teen participants reported that very little mental effort was required to interact with the TDSS while driving, but they also reported the system increased their perceptions of stress while driving. The second phase of the study proposed the information that should be presented in the real-time text messages and to parents in a weekly report. A potential weekly report format is described. Finally, the project identified the issues associated with using the TDSS as an additional tool to support GDL programs.
Development and Field Demonstration of DSRC Based V2V-Assisted V2I Traffic Information System for the Work Zone
(Intelligent Transportation Systems Institute, Center for Transportation Studies, University of Minnesota, 2012-06) Maitipe, Buddhika; Ibrahim, Umair; Hayee, M. Imran
This report describes the architecture, functionality and the field demonstration results of a newly developed DSRC-based V2I work zone traffic information system with V2V assistance. The developed system can automatically acquire important work zone travel information, e.g., the travel time (TT) and the starting location of congestion (SLoC), and relay them back to the drivers approaching the congestion site. Such information can help drivers in making informed decisions on route choice and/or preparing for upcoming congestion. Previously, we designed such a system using DSRC based V2I-only communication, which could not handle longer congestion lengths and the message broadcast range was also very limited. Our current system, on the other hand, can achieve much longer broadcast range (up to a few tens of kms), and can handle much longer congestion coverage length (up to a few kms) by incorporating DSRC based V2I communication with V2V assistance. The new system is also portable and uses only one RSU, which can acquire traffic data by engaging the vehicles traveling on the roadside whether within or outside of its direct wireless access range. From the traffic data, it estimates important traffic parameters, i.e., TT and SLoC, and periodically broadcasts them back to the vehicles approaching the congestion well before they enter the congested area. The results from the field demonstration have indicated that new system can adapt to dynamically changing work zone traffic environments and can handle much longer congestion lengths as compared to the previous system using V2I-only communication without V2V assistance.
Development and Field Demonstration of DSRC-Based V2I Traffic Information System for the Work Zone
(2010-12) Maitipe, Buddhika; Hayee, M. Imran
This report describes the architecture, functionality and the field demonstration of a newly developed dedicated short-range communication (DSRC)-based Vehicle to Infrastructure (V2I) communication system for improving traffic efficiency and safety in the work-zone related congestion buildup on US roadways. The goal was to develop a portable system that can be easily deployed at a work zone site to acquire and communicate important travel information, e.g., travel time (TT) and start of congestion (SoC) location to the driver. By providing this information, i.e., SoC location and TT, drivers can make informed decisions on route choice and be prepared for upcoming congestion. The system is composed of a portable road-side unit (RSU) that can engage the on board units (OBUs) of the traveling vehicles using DSRC technology to acquire necessary traffic data (speed, time, and location). From the acquired data, the RSU periodically estimates the SoC location and TT that are broadcast to all vehicles in its coverage range. An OBU receiving the broadcast message calculates the distance to the SoC location. The distance to the SoC location and TT are then relayed to the driver, who can make smart decisions regarding whether to seek an alternate route and when to expect a sudden speed reduction. Results from the field demonstration have shown that the developed system can adapt to changing work-zone environments smoothly under various congestion patterns on the road.
Development of a Low-Cost Interface between Cell Phone and DSRC-Based Vehicle Unit for Efficient Use of IntelliDrive Infrastructure
(2010-11) Roodell, Beau; Hayee, M. Imran
Intelligent transportation systems (ITS), a mission of the US Department of Transportation, focuses on intelligent vehicles, intelligent infrastructure and the creation of an intelligent transportation system through integration with and between these two components. Dedicated Short Range Communications (DSRC), a tool approved for licensing by the Federal Communications Commission (FCC) in 2003, promises to partially fulfill this mission. This research proposal intends to utilize DSRC technology to communicate the traffic safety information available at central infrastructure to a driver’s cell phone. The specific objective of this research project is to design, build and demonstrate a wireless communication interface device that can act as a traffic-safety-information transportation agent between the DSRC vehicle radio unit and a Bluetooth-enabled cell phone inside a vehicle. By having this interface device along with the DSRC radio unit in a vehicle as a separate entity or integrated with a DSRC unit, any driver will be able to receive the valuable traffic safety messages on a Bluetooth-enabled cell phone. The prototype was demonstrated successfully in multiple road and traffic scenarios by transmitting the traffic safety messages to the Bluetooth-enabled cell phone. The next step is to show effectiveness of this system in a realistic environment for which a workzone environment has been chosen to relay traffic safety messages to vehicles approaching the workzone.
Development of a traffic information system using ad-hoc control and DSRC based V2V communication
(2013-09) Ibrahim, Umair
A lane closure can significantly reduce the vehicles speed through the freeway bottleneck, resulting in the congestion buildup. As the queue length grows past the posted static warning signs in the congested zone surprising many drivers which can greatly increase the probability of rear end vehicle crash. In such circumstances, a real time traffic safety information system could help minimize rear end collisions. Current traffic information systems use radio, internet, or cellular communication to convey the information of congestion to the drivers. This information is generated using static sensor probes that often give a rough estimate of traffic parameters e.g., end-of-queue location, and travel time. Additionally, the update to the traffic data occurs quite infrequently and sometimes is obsolete by the time when a driver receives it. However, these systems suffer from issues such as latency and reliance on third party and/or dedicated infrastructure support.This paper presents architecture, functionality, and field evaluation of a newly developed real-time traffic information system using DSRC based V2V communication without needing any roadside infrastructure support. The developed system utilizes an ad-hoc host vehicle acting as central control from among the DSRC equipped vehicles present on the road to dynamically acquire important traffic parameters such as starting and ending locations of congestion, and travel time. Furthermore, it provides useful traffic alerts to DSRC equipped vehicles to improve drivers' situational awareness. The algorithm designed for the system makes it fully adaptable to any congestion scenario whether due to a work zone or an incident, or due to regular rush hour traffic. The developed system is well suited for operational deployment in future, particularly during the initial phase of the DSRC market penetration, because it incorporates DSRC equipped programmable changeable message signs (PCMSs) to convey the warning messages to non-DSRC equipped vehicles. Furthermore, a rigorous analysis has been conducted to investigate the minimum DSRC market penetration rate needed for the developed system to successfully acquire and disseminate TT and SLoC for the work zone. The results of this analysis suggest that a market penetration rate ranging from 20% to 35% is needed for the system to reliably work.
Development of Real-Time Traffic Adaptive Crash Reduction Measures for the Westbound I-94/35W Commons Section
(University of Minnesota Center for Transportation Studies, 2008-12) Hourdos, John; Xin, Wuping; Michalopoulos, Panos
Much research has been conducted in the development, implementation, and evaluation of innovative ITS technologies aiming to improve traffic operations and driving safety. An earlier project succeeded in supporting the hypothesis that certain traffic conditions are favorable to crashes and in developing real-time algorithms for the estimation of crash probability from detector measurements. Following this accomplishment a natural question is “how can this help prevent crashes?” This project has the ambitious plan of not only answering this question but also providing a multifaceted approach that can offer different types of solutions to an agency aimed at reducing crashes in this and other similar locations. This project has two major objectives; first it aimed at utilizing a cutting edge 3D virtual reality system to design and visualize different driver warning systems specifically for the I-94 westbound high crash location in Minneapolis, MN. Second, in view of the desire of local engineers for a more traditional approach, this project explored the use of existing micro-simulation models in the evaluation of safety improvements for the aforementioned high crash area. This report describes the results of these investigations but more importantly describes the lessons learned in the process of the research. These lessons are important because they highlight gaps of technology and knowledge that hampered this and other research projects with similar objectives.
Emergency Medical Services in American Indian Reservations and Communities: Results of a National Survey
(Center for Transportation Studies, University of Minnesota, 2019-05) Quick, Kathryn; Dufour, Sara; Narváez, Guillermo
The focus of this exploratory study is emergency medical response (EMS) for motor vehicle crashes (MVCs) in American Indian reservations and communities. Tribal transportation professionals have raised questions about the role of EMS in the high MVC fatality rate – 656 annually – in these areas. We conducted a national survey (n=189) of tribal governments, first responders, and state-tribe transportation liaisons. They assessed factors in the quality of EMS response in their areas (e.g., 911 access, dispatch, accessibility of MVC locations, responders’ training and equipment, distance to hospital; and inter-jurisdictional coordination). We recommend continuing research on MVCs specifically in American Indian reservations and communities. Specifically, more research is needed on dispatch issues (e.g., cell phone coverage and dispatchers’ ability to pinpoint MVC sites) because this is study respondents’ single highest area of concern, and the whole EMS response hinges on successfully placing a call for help. And, examples of productive inter-jurisdictional coordination need to be identified since tribes report vastly different experiences with this aspect of EMS system functioning. Two statistically significant findings merit further study, namely: a) heightened concern about response times and hospital access among responders from the Pacific Northwest and Alaska (compared with other regions); and b) higher optimism on all aspects of EMS response from study participants who work for tribal governments versus participants without that affiliation. Finally, it is important for researchers to communicate clearly about the geographic areas covered under “American Indian reservations and communities” in order to improve characterization of road safety and EMS issues.
Enhanced Micro-Simulation Models for Accurate Safety Assessment of Traffic Management ITS Solutions
(University of Minnesota Center for Transportation Studies, 2008-11) Xin, Wuping; Hourdos, John; Michalopoulos, Panos
Much research has been conducted in the development, implementation, and evaluation of innovative ITS technologies aiming to improve traffic operations and driving safety. Existing micro-simulation modeling only describes normative car-following behaviors devoid of weakness and risks associated with real-life everyday driving. This research aims to develop a new behavioral car-following model that is pertinent to the true nature of everyday human driving. Unlike traditional car-following models that deliberately prohibit vehicle collisions, this new model builds upon multi-disciplinary findings explicitly taking into account perceptual thresholds, judgment errors, anisotropy of reaction times and driver inattention, in order to replicate “less-than-perfect” driving behavior with all its weakness and risks. Most importantly, all parameters of this model have direct physical meaning; this ensures vehicle collisions are replicated as a result of behavioral patterns rather than simply being numerical artifacts of the model. Meanwhile, vehicle trajectories were extracted from real-life crashes collected from a freeway section of I-94WB This is by far the first data collection efforts that aim to collect vehicle trajectories from real-life crashes to aid car-following modeling. These data were employed in this study to test, calibrate and validate the model. This new model is successful in replicating these vehicle trajectories as well as crashes.
Estimation of Crossing Conflict at Signalized Intersection Using High-Resolution Traffic Data
(Minnesota Department of Transportation, 2017-03) Liu, Henry X.; Davis, Gary A.; Shen, Shengyin; Di, Xuan; Chatterjee, Indrajit
This project explores the possibility of using high-resolution traffic signal data to evaluate intersection safety. Traditional methods using historical crash data collected from infrequently and randomly occurring vehicle collisions can require several years to identify potentially risky situations. By contrast, the proposed method estimates potential traffic conflicts using high-resolution traffic signal data collected from the SMART-Signal system. The potential conflicts estimated in this research include both red-light running events, when stop-bar detectors are available, and crossing (i.e. right-angle) conflicts. Preliminary testing based on limited data showed that estimated conflict frequencies were better than AADT for predicting frequencies of angle crashes. With additional validation this could provide a low-cost and easy-to-use tool for traffic engineers to evaluate traffic safety performance at signalized intersections.
Evaluation and Refinement of Minnesota Queue Warning Systems
(Minnesota Department of Transportation, 2023-03) Hourdos, John; Robbennolt, Jake
This study evaluates the first and a second implementations of the MN-QWARN queue warning algorithm developed by Hourdos et al. (1). This algorithm was developed to detect specific crash prone conditions created by traffic oscillations (shockwaves) on freeway systems. The MN-QWARN system was specifically calibrated for the freeway studied in Hourdos et al. (1) and was moved to a new location with minimal calibration. This evaluation found that the right-side model had a detection rate of 25% and a false alarm rate of 36%. The left-side model had a detection rate of 64% and a false alarm rate of 23%. We also note high over-warning rates on both lanes. Based on these findings, we recommend recalibrating the MN-QWARN algorithm at this location to examine improvements in performance.
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.
Evaluation of the Smart Work Zone Speed Notification System
(Minnesota Department of Transportation., 2019-06) Hourdos, John; Parikh, Gordon; Dirks, Peter; Lehrke, Derek; Lukashin, Pavel
The Smart Work Zone Speed Notification (SWZSN) system aims to alleviate congestion, queuing, and rear end crashes in work zones by informing drivers of the speed of the downstream segment using a type of portable Intelligent Lane Control System (ILCS), Portable Changeable Message Signs (PCMS). The hypothesis was that drivers, knowing the speed up to 1 mile downstream, will slow down early or at least be alert and perform smoother decelerations. Video of the SWZSN was analyzed over two years of operation by the Minnesota Traffic Observatory. Overall, the system resulted in beneficial reductions of selected decelerations by the drivers. In situations where the messages communicated to the drivers were consistent and accurate, reductions of more than 30% in the selected deceleration rates were observed. Unfortunately, there were several cases where counterproductive or misleading messages were communicated to the drivers, prompting relative increases to the selected deceleration rates. The most important observation, stemming from both positive and negative influences, was that the speed notification system was noticed by drivers and resulted in a statistically significant influence on driving behavior, unlike other driver alert systems.
Examining Optimal Sight Distances at Rural Intersections
(Minnesota Department of Transportation., 2019-07) Morris, Nichole L.; Craig, Curtis M.; Achtemeier, Jacob D.
Decisions made regarding driver sight distance at rural intersections are complex and require considerations for safety, efficiency, and environmental factors. Sight distance, cross-traffic velocity, and vehicle placements significantly affect driver judgment and behavior atthese intersections. A series of rural, two-lane thru-STOP simulated intersections with differing sight distances and traffic speeds were created and then validated by county and state engineers. Experimental data from 36 participants in a time-to-collision (TTC) intersection crossing judgment task and a rural highway thru-STOP intersection driving simulation task was analyzed to clarify the influence of rural thru-STOP intersection characteristics on driving performance and decision-making. Results demonstrated that longer sight distances of1,000 ft. and slower crossing speeds (i.e., 55 mph) were more accommodating for participants attempting to select gaps and cross from the minor road, corresponding with (1) lower mental workload, perceived risk, difficulty, and anxiousness, and (2) better performance in terms of estimated crash rate, and larger TTCs. Second, longer distances of 1,000 ft. appear to aid drivers’ responsiveness on the main road approaching an intersection, specifically when another driver on the minor road runs the stop sign. Minor road drivers positioned close tothe roadway at the stop sign, compared to standard stop bar placement, tended to help reduce the speed of main road drivers. Overall,results demonstrated a systematic improvement in the performance of both minor and major road drivers with the implementation of a1,000-foot sight distance at rural thru-STOP intersections.
Identifying Deer Vehicle Collision Concentrations in Minnesota
(Minnesota Department of Transportation, 2023-11) Stern, Raphael; Moen, Ron; Zare, Arian; Bober, Marissa
Deer-vehicle collisions (DVCs) represent a significant hazard on Minnesota roads, with roughly 1,200 DVCs reported annually to the Minnesota Department of Public Safety (MnDPS) and many more going unreported. While DVCs are common across Minnesota, local variations in deer density as well as roadway characteristics and use patterns make DVCs more likely to occur on some roadways than others. Moreover, the true extent of DVC concentrations is unclear due to the high proportion of DVCs that go unreported. This report presents findings from research that (1) uses data to identify areas of DVC concentration based on the specific roadway characteristics and (2) presents a methodology to estimate DVC reporting rate across the state. This methodology is applied in a pilot study in the Duluth area, as well as in an extended search area that includes highways spread across much of outstate Minnesota to estimate the DVC reporting rate.
Improving intersection safety through variable speed limits for connected vehicles
(Center for Transportation Studies, University of Minnesota, 2019-05) Levin, Michael; Chen, Rongsheng; Liao, Chen-Fu; Zhang, Tab
Autonomous vehicles create new opportunities for innovative intelligent traffic systems. Variable speed limits, which is a speed management systems that can adjust the speed limit according to traffic condition or predefined speed control algorithm on different road segments, can be better implemented with the cooperation of autonomous vehicles. These compliant vehicles can automatically follow speed limits. However, non-compliant vehicles will attempt to pass the moving bottleneck created by the compliant vehicle. This project builds a multi-class cell transmission model to represent the relation between traffic flow parameters. This model can calculate flows of both compliant and non-compliant vehicles. An algorithm is proposed to calculate variable speed limits for each cell of the cell transmission model. This control algorithm is designed to reduce the stop-and-go behavior of vehicles at traffic signals. Simulation is used to test the effects of VSLs on an example network. The result shows that VSL is effective at reducing the energy consumption of the whole system and reduce the likelihood of crash occurrence.
Investigation of the Impact of the I-94 ATM System on the Safety of the I-94 Commons High Crash Area
(Minnesota Department of Transportation, 2014-05) Hourdos, John; Zitzow, Stephen
Active Traffic Management (ATM) strategies are being deployed in major cities worldwide to deal with pervasive system congestion and safety concerns. While such strategies include a diverse array of components, in the Twin Cities metropolitan area the deployment of the Intelligent Lane Control Signs (ILCS) allowed for the implementation of Variable Speed Limits (VSL). The VSL system in the Twin Cities aims to detect congestion and preemptively warn upstream drivers to reduce speed. By reducing the severe change in speed between upstream and downstream traffic, safety and operational benefits are sought. This report presents an investigation of the effect the I-94 VSL system has on the safety of the high frequency crash area located on the westbound lanes of the freeway through downtown Minneapolis (I-94/I-35W commons). This report describes several methodologies that were used to examine the impact of the VSL system within the I-94/I-35W commons high crash area. Numerous data sources were utilized, including video records of crash and near crash events, loop detector traffic measurements, machine vision sensor data, and actuations from the VSL system. A before-after approach was taken to examine the incident rates for crashes and near crashes using visually identified events within video data. Utilizing the unique capabilities of the Minnesota Traffic Observatory’s I-94 Freeway Lab, high resolution traffic measurements, collected by machine vision sensors at the bottleneck location, were used within a new cross-correlation based analysis methodology to measure and visualize shockwave activity before and after the implementation of the VSL system.

University Digital Conservancy

Browse by Subject

Browsing by Subject "Traffic safety"