Discharge Flow Rate Change Under Rainy Conditions on Urban Motorways

  • Göker Aksoy Istanbul Technical University
  • Kemal Selçuk Öğüt Istanbul Technical University
Keywords: discharge flow, capacity drop, rain effect, motorway

Abstract

Queue discharge flow is the most frequently observed phenomenon on urban motorways when demand exceeds capacity. Once a queue is formed, congestion arises, and the number of vehicles that can pass from downstream reduces. This reduction phenomenon is defined as the capacity drop and calculated by taking the difference between capacity and discharge flow at a road section. Obviously, this capacity drop exists after an onset of congestion and may increase in relation to weather conditions, such as rain, snow, or fog, which cause longer queues and delays. In this paper, the effect of rain on discharge flows is investigated and compared with sunny days on Istanbul urban motorways. Besides, rain precipitation during congestion is considered and related to discharge flow. Four different motorway sections were analyzed, and up to 37% discharge flow reduction was determined between sunny and rainy conditions. Motorway sections with higher free flow speed (FFS) were found to be more affected by rain, and discharge flow reduction was bigger compared to the section with the lowest FFS. For 1 mm/m2/h of precipitation, the discharge flow is estimated as 1,719 pcu/h/lane when FFS is 84 km/h, and as 1,560 pcu/h/lane if FFS is 104 km/h.

Author Biographies

Göker Aksoy, Istanbul Technical University

ITU Civil Engineering Faculty, Transportation Division

Research Assistant

Kemal Selçuk Öğüt, Istanbul Technical University

ITU Civil Engineering Faculty, Transportation Division

Prof. Dr. 

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Published
2018-12-28
How to Cite
1.
Aksoy G, Öğüt K. Discharge Flow Rate Change Under Rainy Conditions on Urban Motorways. Promet - Traffic & Transportation [Internet]. 28Dec.2018 [cited 22Apr.2019];30(6):733-44. Available from: http://traffic.fpz.hr/index.php/PROMTT/article/view/2940
Section
Articles