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Journal of Advanced Transportation
Volume 2017 (2017), Article ID 8391325, 13 pages
Research Article

Estimating Safety Effects of Green-Man Countdown Devices at Signalized Pedestrian Crosswalk Based on Cellular Automata

1The Key Laboratory of Road and Traffic Engineering, Ministry of Education, Shanghai 201804, China
2College of Transportation Engineering, Tongji University, 4800 Cao’an Road, Shanghai 201804, China
3Centre for Infrastructure Systems, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798

Correspondence should be addressed to Chen Chai

Received 31 July 2016; Revised 18 January 2017; Accepted 13 March 2017; Published 7 June 2017

Academic Editor: Richard S. Tay

Copyright © 2017 Chen Chai et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Safety effects of Green-Man Countdown Device (GMCD) at signalized pedestrian crosswalks are evaluated. Pedestrian behavior at GMCD and non-GMCD crosswalks is observed and analyzed. A microsimulation model is developed based on field observations to estimate safety performance. Simulation outputs allow analysts to assess the impacts of GMCD at various conditions with different geometric layout, traffic and pedestrian volumes, and the green time. According to simulation results, it is found that the safety impact of GMCD is affected by traffic condition as well as different time duration within green-man signal phase. In general, GMCD increases average walking velocity, especially during the last few seconds. The installation of GMCD improves safety performance generally, especially at more crowded crossings. Conflict severity is increased during last 10 s after GMCD installation. Findings from this study suggest that the current practice, which is to install GMCD at more crowded crosswalks or near the school zone, is effective. Moreover, at crosswalks with GMCD, longer all red signal phase is suggested to improve pedestrian safety during intergreen period.