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.

References

Banks JH. Two-Capacity Phenomenon at Freeway Bottlenecks: A Basis for Ramp Metering? Transportation Research Record: Journal of the Transportation Research Board. 1991;1320: 83-90.

Banks JH. The Two-Capacity Phenomenon: Some Theoretical Issues. Transportation Research Record: Journal of the Transportation Research Board. 1991;1320: 234-241.

Hall FL, Agyemang-Duah K. Freeway Capacity Drop and The Definition of Capacity. Transportation Research Record: Journal of the Transportation Research Board. 1991;1320: 91-98.

Papageorgiou M, Hadj-Salem H, Blosseville JM. ALINEA: A Local Feedback Control Law for On-ramp Metering. Transportation Research Record: Journal of the Transportation Research Board. 1991;1320: 58-64.

Papageorgiou M, Diakaki C, Dinopoulou V, Kotsialos A, Wang Y. Review of Road Traffic Control Strategies. Proceedings of the IEEE, December 2003, 2003:91(32): 2043-2067.

Cassidy MJ, Rudjanakanoknad J. Increasing the Capacity of an Isolated Merge by Metering its On-ramp. Transportation Research Part B: Methodological. 2005:39(10): 896-913.

Elefteriadou L, Lertworawanich P. Defining, Measuring and Estimating Freeway Capacity. Transportation Research Board 82nd Annual Meeting compendium of papers CD-ROM, January 12-16, 2003, Washington, DC; 2003.

Chung K, Rudjanakanoknad J, Cassidy MJ. Relation Between Traffic Density and Capacity Drop at Three Freeway Bottlenecks. Transportation Research Part B: Methodological. 2007;41(1): 82-95.

Yuan K, Knoop VL, Leclercq L, Hoogendoorn SP. Capacity Drop: A Comparison Between Stop-and-Go Wave and Queue Congestion at Lane-Drop Bottleneck. Transportmetrica B: Transport Dynamics. 2017;5(2): 145-158.

Öğüt KS, Banks J.H. Stability of Freeway Bottleneck Flow Phenomena. Transportation Research Record: Journal of the Transportation Research Board. 2005;1934: 108-115.

Lakshmi K, Öğüt KS, Banks JH. Evaluation of N-Curve Methodology for Analysis of Complex Bottlenecks. Transportation Research Record: Journal of the Transportation Research Board. 1999;2007: 54-61.

Srivastava A, Geroliminis N. Empirical Observations of Capacity Drop in Freeway Merges with Ramp Control and Integration in a First-Order Model. Transportation Research Part C: Emerging Technologies. 2013;30: 161-177.

Bertini RL, Malik S. Observed Dynamic Traffic Features on Freeway Section with Merges and Diverges. Transportation Research Record: Journal of the Transportation Research Board. 2004;1867: 25-35.

Bertini RL, Leal M. Empirical Study of Traffic Features at a Freeway Lane Drop. ASCE Journal of Transportation Engineering. 2005;131(6): 397-407.

Cassidy MJ, Bertini RL. Some Traffic Features at Freeway Bottlenecks. Transportation Research Part B: Methodological. 1999;33: 25-42.

Oh S, Yeo H. Estimation of Capacity Drop in Highway Merging Sections. Transportation Research Record: Journal of the Transportation Research Board. 2012;2286: 111-121.

Jia A, Williams B, Rouphail N. Identification and Calibration of Site-Specific Stochastic Freeway Breakdown and Queue Discharge. Transportation Research Record: Journal of the Transportation Research Board. 2010;2188: 148-155.

Transportation Research Board. Highway Capacity Manual. Transportation Research Board, National Research Council, Washington, D.C; 2010.