Report No. Government Accession No. Recipient’s Catalog No. Title and Subtitle Failure Analysis of Network Based Accessible Pedestrian Signals in Closed-Loop Operation Report Date March 2011 Performing Organization Code KLK719 Author(s) Wall, Dr. Richard; Johnson, Dr. Brian; Kyte, Dr. Michael Performing Organization Report No. N11-02 Performing Organization Name and Address Work Unit No. (TRAIS) National Institute for Advanced Transportation Technology University of Idaho PO Box 440901; 115 Engineering Physics Building Moscow, ID 83844-0901 Contract or Grant No. DTRT07-G-0056 Sponsoring Agency Name and Address US Department of Transportation Research and Special Programs Administration 400 7th Street SW Washington, DC 20509-0001 Type of Report and Period Covered Final Report: August 2009 February 2011 Sponsoring Agency Code USDOT/RSPA/DIR-1 Supplementary Notes: Abstract The potential failure modes of a network based accessible pedestrian system were analyzed to determine the limitations and benefits of closed-loop operation. The vulnerabilities of the system are accessed using the industry standard process know as Failure Modes and Effects Analysis. This analysis reveals that because the closed-looped operation increases operational observability, there is only one failure mode that is not detectible. Investigation on reliability of hardware and software indicate that the probability of this particular event is extremely low. The three primary components of a distributed control system are hardware, software, and communications. Environmental conditions are the predominant factors that determine hardware reliability. The system was tested for its ability to function in the presence of electrical transients specified my NEMA. All hardware components meet or exceed NEMA temperature requirements. Software errors are difficult to detect and difficult to predict. Best practices in development and testing can minimize the number of errors. Testing includes multiple years of both laboratory and field testing. Key Words Traffic control devices; traffic signal control systems; signalized intersections; warning devices for the handicapped; pedestrian safety; pedestrian areas; pedestrian vehicle interface. Distribution Statement Unrestricted; Document is available to the public through the National Technical Information Service; Springfield, VT. Security Classif. (of this report) Unclassified Security Classif. (of this page) Unclassified No. of Pages 23 Price … Form DOT F 1700.7 (8-72) Reproduction of completed page authorized time
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