Post encroachment time threshold identification for right-turn related crashes at unsignalized intersections on intercity highways under mixed traffic

Abstract Spirally arranged and physically separated traffic lanes in the circulatory carriageway of turbo-roundabouts force drivers to choose a particular entry lane and, subsequently, a circulatory traffic lane according to their intended destination. This specificity is taken into account in theoretical capacity models for two-lane turbo-roundabout entries typically evaluated by the lane-by-lane approach. Nevertheless, this specific path of movements is not considered in the most widely used capacity models for single-lane minor entries at oval turbo-roundabouts. In these models, only one entering traffic flow conflicted by two circulating traffic flows in front of the entry is considered. However, the entering traffic flow presents a mixed traffic flow of two movements (right-turning movement and left-turning and through movement) with different capacities due to different number of conflicting traffic streams and traffic volumes allocated into the outer and the inner circulatory lane. This fact is included in the capacity estimation for a single-lane minor entry presented in the article using the existing capacity formula for the mixed traffic flow on a shared minor lane at unsignalized intersections. The entry capacity reflects the proportion of the right-turning movement within a shared entry lane as well as the specific allocation of circulating traffic flow into the outer and the inner circulatory lane. This entry capacity is about 10 % to 30 % higher compared to a single-lane entry capacity estimated according to commonly used models described in the article. Higher entry capacity in a higher proportion of the right-turning traffic within mixed entry traffic flow is confirmed also by the results of average delays estimated by the theoretical delay model and microsimulation.

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Capacity of Unsignalized Intersections with Mixed Vehicle Flows

Transportation Research Record Journal of the Transportation Research Board ◽

10.3141/1852-32 ◽

2003 ◽

Vol 1852 (1) ◽

pp. 265-270 ◽

Cited By ~ 2

Author(s):

Wenquan Li ◽

Wei Wang ◽

Dazhi Jiang

Keyword(s):

Traffic Flow ◽

Field Testing ◽

Mixed Traffic ◽

Vehicle Type ◽

Traffic Conditions ◽

Unsignalized Intersections ◽

Capacity Theory ◽

Capacity Model ◽

Set Up ◽

Gap Acceptance Theory

On the basis of gap-acceptance theory, mixed traffic flow composed of two representative vehicle types—heavy and light vehicles—is analyzed with probability theory. A capacity model is set up for an unsignalized intersection in which the minor-stream mixed traffic flows cross m major lanes and the traffic flow headways fit the M3 distribution; it is an extension of minor-lane capacity theory for one vehicle type and one major-stream traffic flow. A more complicated case with minor-stream flow composed of discretionary vehicle types is also considered, and the corresponding formula is given. After field testing in China, the conclusion is drawn that this model is better for analyzing Chinese traffic conditions than are other existing models.

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Study of Bicycle Movements in Conflicts at Mixed Traffic Unsignalized Intersections

IEEE Access ◽

10.1109/access.2017.2703816 ◽

2017 ◽

Vol 5 ◽

pp. 10108-10117 ◽

Cited By ~ 11

Author(s):

Ronghui Zhang ◽

Jianping Wu ◽

Ling Huang ◽

Feng You

Keyword(s):

Mixed Traffic ◽

Unsignalized Intersections

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Effect of vehicle composition and delay on roundabout capacity under mixed traffic conditions

Archives of Transport ◽

10.5604/08669546.1225456 ◽

2016 ◽

Vol 40 (4) ◽

pp. 7-14 ◽

Cited By ~ 3

Author(s):

Dodappaneni Abhigna ◽

Sindhu Kondreddy ◽

K. V. R. Ravi Shankar

Keyword(s):

Simulation Model ◽

Travel Time ◽

Andhra Pradesh ◽

Study Data ◽

Mixed Traffic ◽

Capacity Estimation ◽

Traffic Conditions ◽

Unsignalized Intersections ◽

The World ◽

Estimation Models

Roundabouts are replacing conventional unsignalized intersections in many parts of the world (Polus and Shmueli, 1997). Capacity estimation is necessary for designing a new roundabout, to analyze and improve the existing roundabout facilities. There are several methods to estimate the capacity of the roundabout, but most of them are for homogeneous lane based traffic conditions and not applicable for mixed traffic conditions. This study tries to find out the applicability of the existing methods to mixed traffic conditions, identify the effect of vehicle composition, travel time and delay on capacity. In this study, data was collected from two roundabouts located in Mysore, Karnataka and Rajahmundry, Andhra Pradesh in India. Capacities for both the roundabouts are calculated using the existing methods and compared. VISSIM simulation model has been developed and analyzed for different vehicle compositions scenarios. It was observed that vehicle composition of the traffic influences the roundabout capacity. Since the entry capacity of a roundabout varies significantly with the vehicle composition of the traffic at the roundabout, it is necessary to incorporate this factor into the existing capacity estimation models.

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