KLK561: Improving Safety at Signalized Intersections During Inclement Weather Conditions: Full Description
ITD Research Project 216; Task Order Number UI-12-01
Principal Investigators:
- Ahmed Abdel-Rahim
- Axel Krings
- Michael Dixon
ITD Project Manager:
- Brent Jennings
FHWA Project Advisor:
- Lance Johnson
Research Problem Statement:
Adverse weather conditions such as rain and snow can reduce pavement friction and visibility distance, impairing the ability of drivers to operate their vehicles safely, reducing roadway capacity and significantly affecting system efficiency. Several empirical studies in the literature have investigated the effect of inclement weather on various signal timing traffic parameters. In terms of weather effect on highway safety, several studies found that weather significantly increases crash risk. Weather-related crash fatalities account for 17 percent of all traffic fatalities each year. One study suggests that snow increases crash risk by approximately 120, 80, 40, and 40 percent for minimal, minor, major, and fatal injuries, respectively. Existing studies collectively show that traffic signal timing used under normal conditions becomes problematic under adverse weather for two primary reasons. First, reductions in average speeds and saturation flow rates and the increase in start-up delays make normal signal timing unsuitable during inclement weather. Second, with reduced pavement friction and visibility, default all-red and yellow clearance intervals become unsafe as motorists are more likely to be trapped in dilemma zones. The goal of this project is to develop and implement a real-time weather-responsive traffic signal control system for the state of Idaho with the intent to improve the efficiency and safety of traffic signal operations during inclement weather. This system will receive and use weather information from the FHWA’s Clarus weather data system and from the state’s Road Weather Information Stations (RWIS) to adapt signal timing in response to inclement weather. Five innovations are necessary to fully achieve the proposed project goal. First, the system will operate and achieve its potential using current traffic controller and controller cabinet technologies. Second, the system will be compatible with future applications within the Federal Highway Administration’s connected-vehicle initiative. Third, minimal hardware, in addition to traffic controllers, will be required for full implementation. Fourth, computer driven algorithms will implement traffic signal control decisions using Clarus data. Fifth, software design will incorporate self diagnostic techniques for fault detection and recovery to maximize security and survivability and minimize cost.
Project Objectives:
Develop and pilot a real-time weather-responsive traffic signal control system for the state of Idaho with the intent to improve the efficiency and safety of traffic signal operations during inclement weather. This system will receive and use weather information from the FHWA’s Clarus weather data system and from the state’s Road Weather Information Stations (RWIS) to adapt signal timing in response to inclement weather.
Project Tasks
Review and document pertinent information from state, Federal and commercial databases. This will include a thorough review and evaluation of the literature on real time weather response systems and methods used to improve safety at signalized intersections. These searches will be periodically updated throughout the project to keep current with new research. A brief overview of theory and practices related to these topics will be provided to the TAC.
This includes Clarus weather stations and RWIS throughout the state that are relevant to the project scope. This task will also include a documentation of the type of traffic controllers used and their NTCIP computability.
Meet with the project’s TAC committee to identify the intersection(s) included in the prototype field implementation. Final approval of sites must be given in writing by ITD's Project Manager.
Define system specification. This task has several subtasks in which the system specifications will be derived. These specifications will provide basis for hardware and software.
System Design: System design involves designing several fundamental components according to specifications: the system hardware, the interfacing technology, and the system operational software and contingency management system. Industry design processes will be adopted, where designs are subjected to peer review in project meetings in which each part of the system and code will be presented to the team. In this way, specifications will be adhered to rigorously.
Data Interface and Analysis. This task will be performed in parallel with System Design and it addresses the practical implications of Clarus and RWIS data communications and data manipulation in the local processing units. This task includes the derivation of a scalable local Clarus client.
System Verification and Timing Analysis. The proposed weather responsive system will be tested and evaluated in the lab through a hardware-in-the-loop simulation (HILS) model. The HILS model used in this project includes a workstation running the VISSIM microscopic simulation model for the network, a traffic controller, a controller interface device (CID) to facilitate the exchange of data between the simulation model and the traffic controller, and an external processing unit that runs the software application and the weather responsive control algorithm and is connected to both the Clarus system and the traffic controller. This pre-deployment testing will verify the system operations prior to field implementation of the system. This task addresses standalone system testing and integrated systems testing and analysis. System verification in the context of design for survivability is more complicated than in a traditional approach that does not design the security and survivability considerations into the system. In the proposed work, the system will be studied in real time to observe its behavior in the presence of induced malicious acts and other faults. The interplay of functionality execution and adaptive control will be studied to determine how the algorithm selection processes affect traffic signal timing and measure the efficiency with which the controller monitoring functions execute.
Field implementation, monitoring, and evaluation. The proposed weather responsive system will be implemented in one or more intersections in the state system during the months of November 2012 and January 2013. The performance of the system and the traffic controller(s) will be monitored and documented throughout the test period. The data will be used in the system evaluation analysis. A demonstration of project equipment will be given to ITD and FHWA-Idaho at a location to be determined.
Project final report: The project final report will document the analysis and evaluation of the proposed system. It will also include a summary of all project tasks and research activities. The research team also plans to prepare a brief brochure on the proposed system that is to be used for technology transfer.
Project Communication Schedule:
Monthly project progress report (ITD 771).
Quarterly project meeting with the project's technical oversight committee. (via video or teleconferences)
Needs and Requirements:
This research project aligns with Idaho’s Strategic Highway Safety Plan and supports the top performance measure of eliminating fatalities and serious injuries on all Idaho roadways through the design and implementation of real-time weather responsive traffic signal systems.
Required Output
- Comprehensive literature review within the first 3 months, with periodic updates with each quarterly report.
- Quarterly reports to be delivered at each quarterly meeting of the TAC.
- A list of all chosen sites for inclusion in the project.
- A brief written overview of theory and practices related to real-time weather response systems and improving safety at signalized intersections.
- Provide an on-site demonstration and training of the project equipment for ITD Headquarters and district personnel.
- Write a final report describing the findings of this research along with the researcher's conclusions, cost versus benefit analysis and recommendations.
- Present study findings and recommendations to ITD's Board and/or Executive Team, if requested.
Implementation:
The weather responsive system developed as part of this project provides a prototype that will allow for implementation of weather responsive traffic signal system applications throughout the state of Idaho.
Expected Outcomes/Savings to ITD:
Benefits to ITD and to the public from this project include: safe and more efficient signalized intersection operations for signalized intersections in the state highway system and the local highway systems, reduction in weather-related crashes which in-turn reduces the economic cost impact of crashes for all Idahoans, reduction in weather-related delay at signalized intersections, reduction in 52198 ITD/ISP cost of manually managing some traffic signals during inclement weather conditions, and increase in public awareness of issues involving signalized intersections operations during inclement weather conditions through the project’s outreach activities.