Modeling Critical Gap of Al Turkmani Roundabout in Baghdad City

Shadhan, Laith Q.; Alkaissi, Zainab A.

doi:10.30684/etj.v40i5.1628

	Modeling Critical Gap of Al Turkmani Roundabout in Baghdad City
Engineering and Technology Journal
Article 9, Volume 40, Issue 5, 2022, Pages 722-731 PDF (1.22 M)
DOI: 10.30684/etj.v40i5.1628
Authors
Laith Q. Shadhan^* ; Zainab A. Alkaissi
Highway and Transportation Dept, College of Engineering, Mustansiriyah University, Baghdad, Iraq
Abstract
Interest in how roundabouts can most effectively be used continues to increase to achieve goals of safety, efficiency, along with other benefits. This research presents the most important element of the operational performance of roundabout traffic intersections in Baghdad city on capacity analysis. The obtained results for critical headway time are (3.35 sec) and (2.8 sec) for the Main west and East approaches. Also, the critical gap value for the West and East approach is less than the range of (NCHRP 572), possibly attributed to the congested traffic volume in Al Turkman roundabout with aggressive driver behavior. Calculating in the west and East approaches peak period (1:00-2:00) pm to describe the rejected and accepted gaps with ranges from (1.00 – 5.00) sec, the main aim of this research is to model the critical headway by analyzing the data in trial and error technique to determine the shape of the data through Probability density function and Cumulative Density Function, and the Mathematical function that represented, exponential distribution functions for critical gaps with different shape functions scale (1,1.5) for accepted and rejected gaps are better fittings to the empirical distribution, and there is no significant difference. Comparing the observed field data and the theoretical data for the validation process of Rejected and Accepted Gaps are done. A good fit is obtained, and a scatterplot for observed and theoretical data has been drawn for the West and East approaches at peak period (1:00-2:00) pm.
Highlights
A good fit is gained for the West and East approaches at peak periods of (1:00-2:00) pm. For both West and East approach, the validation showed a strong linear relationship between the observed field data and the theoretical data. The critical gap’s value for the West and East approach is less than the range of (NCHRP 572).
Keywords
Roundabout; Critical Time Headway; Probability Density Function; Accepted gaps; Statistical Distribution

References
[1] Irvena J., Randhl S., (2010), Analysis of gap acceptance in a saturated two-lane roundabout and implementation of critical gaps in VISSIM, Lund University. [2] Ferrari, P., Giannini, F., Ingegneria stradale: geometria e progetto distrade, ISEDI, (1994) 228–230. [3] Raff, M.S., and Hart, J.W, A volume warrant for urban stop signs. The Eno Foundation for Highway Traffic Control, 1950. [4] Garber, N.J. and Hoel, L.A., Fundamental principles of traffic flow, West Publishing Comp., (1996) 179–182. [5] NCHRP, National Cooperative Highway Research Program, (2007), Roundabouts in the United States, NCHRP Report 572, Transportation Research Board of the National Academies. [6] Al-Ghamdi S (2001) Analysis of time headways on urban roads: a Case study from Riyadh. J Transp Eng-ASCE 127 (4) 289-294. [7] Al-Ghamdi, A.S., (1999) Modeling vehicle headways for low traffic lows on urban freeways and arterial roadways. Proceeding of the 5th International Conference on Urban Transport and the Environment for the 21st Century. Rhodes, Greece. [8] Abtahi S M, Tamannaei M, Haghshenash H (2011) Analysis and modelling time headway distributions under heavy traffic flow conditions in the urban highways: case of Isfahan. Transport. 26 (4) 375-382. [9] Edigbe et al. (2014) Headway Distributions Based on Empirical Erlang and Pearson Type III Time Methods Compared. Research Journal of Applied Sciences, Eng. Technol. J., 7(21) 4410-4414. [10] Alkaissi Z. A. (2018) Analytical Study of Headway Time Distribution on Congested Arterial: A case Study Palestine Road in Baghdad City. Proceedings of the 2nd GeoMEast International Congress and Exhibition on Sustainable Civil Infrastructures, Egypt 2018 – The Official International Congress of the Soil-Structure Interaction Group in Egypt (SSIGE), pp 85-97.
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