Impact of Pedestrian Traffic on Saturation Rate of Protected Left-Turn at Urban Intersections


Heavily congested intersections in metropolitan areas in China are facing unique problems due to high travel demand and a high degree of traffic law violations. Based on a study conducted by the authors of this paper, 93% of left-turn vehicles turning left in these areas were slowed in order to avoid conflict with pedestrians. Intertwined pedestrian and vehicular flows can significantly reduce the capacity of exclusive left-turn lane group through reducing saturation flow rate, which increases the congestion at intersections. This paper investigates how the saturation flow rate of exclusive left-turn lane group is affected by the characteristics of pedestrian flow. By analyzing the imagery data collected by video cameras installed at intersections, the research team is able to obtain the characteristics of both vehicular and pedestrian flows, such as speed and spatial locations. The average operating speed at the saturation flow rate with and without pedestrian traffic is used as a direct measurement to evaluate the effect of pedestrians. Based on the statistical analysis, the paper concludes that saturation flow rate is mainly affected by the position of pedestrian in the crosswalk (inside or outside of left-turn vehicle’s trajectory), and the distance between the vehicle and pedestrians. In general, when the distance is less than four meters, the smaller the distance between vehicle and pedestrians, the larger the impact. However, there is no significant impact when the distance is larger than four meters. To accurately quantify the effect, the degree of pedestrian-vehicle impact is defined in four levels. The results show that the difference in the saturation flow rate between the best and the worst level could be 15.7%, which clearly indicates how important it is to enforce pedestrian crossing behavior.

Share and Cite:

Chen, Y. , He, Y. and Sun, X. (2015) Impact of Pedestrian Traffic on Saturation Rate of Protected Left-Turn at Urban Intersections. Open Journal of Applied Sciences, 5, 22-31. doi: 10.4236/ojapps.2015.51003.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] Viney, N.D. and Pretty, R.L. (1982) Saturation Flow of a Movement Subject to a Pedestrian Stream at Traffic Signals. Proceedings of the Eleventh Australian Road Research Board Conference, University of Melbourne, 23-27 August 1982, 157-166.
[2] Coeymans, J.E. and Herrera, J.C. (2003) Estimating Values for Traffic Parameters in Turning Lanes. Journal of the Transportation Research Board, 1852, 47-54.
[3] Chen, X.M. (2008) Theoretical Research for Capacity of Signalized Intersection on Urban Road Network in Mixed Traffic Condition .Beijing Jiaotong University, Beijing, 49-55.
[4] Xu, J.Q. and Chen, X.W. (2008) Fundamentals of Traffic Engineer. 3rd Edition, China Communication Press, Beijing, 120-121.
[5] Wei, H. and Ren, F.T. (1993) Non-Motorized Transport Interference in Motor Vehicle Flow at Urban Intersections. Journal of Beijing University of Technology, 19, 72-79.
[6] Wei, H., Lu, F., Hou, G. and Mogharabi, A. (2003) Nonmotorized Interference and Control Measures at Signalized Intersections in China. Journal of the Transportation Research Board, 1846, 44-49.
[7] Transportation Research Board (2010) Highway Capacity Manual. National Research Council, Washington DC.
[8] Xu, L.J. and Wang, W. (2006) Analysis of Influence of Left-Turn Non-Motors in Signalized Intersection. China Journal of Highway and Transport, 19, 89-92.
[9] Chen, Z.Q. (2009) Analysis and Modeling on Characteristics of Through Vehicles’ Movement at Signalized Intersections with Mixed Traffic. Beijing Jiaotong University, Beijing, 65-80.
[10] Qian, D.L., Jiang, H.F., Huang, D., et al. (2006) On the Effect of Interference Caused by Mixed Traffic at Signalized Intersection. Journal of Transportation Systems Engineering and Information Technology, 6, 75-78.
[11] Varhelyi, A. (1998) Drivers’ Speed Behavior at a Zebra Crossing: A Case Study. Accident Analysis and Prevention, 30, 731-743.

Copyright © 2021 by authors and Scientific Research Publishing Inc.

Creative Commons License

This work and the related PDF file are licensed under a Creative Commons Attribution 4.0 International License.