Fig 1.
Examples of U-turn design applications.
a:Michigan U-turn Design. b:Texas U-turn Design.
Fig 2.
Illustration of ESUL design on provincial trunk highway.
W:West, E:East, N:North, S:South.
Fig 3.
Illustration of ESUL design.
Table 1.
Geometric parameters of ESUL.
Fig 4.
A median opening at northwest corner 2nd loop road in Xi’an.
Coordinates:108.903898,34.301482. a:The U-turn median opening location schematic. b: The present median opening graphic took by a drone at height of 150m.
Fig 5.
Speed and trajectories of east to west flows.
a:Speed of vehicles from East to West. b: Trajectories of vehicles from East to West.
Fig 6.
Speed and trajectories of west to east vehicles.
a:Speed of vehicles from West to East. b: Trajectories of vehicles from West to East.
Table 2.
Collect vehicle information of the investigation.
Fig 7.
The 24-hour congestion trend of major cities from 2015 to 2017 [51].
The morning peak appeared from 07:00∼09:00, the evening peak appeared from 17:00∼19:00, and the valley, excluding late night, appeared from 12:00∼14:00.
Fig 8.
The 24-hour congestion delay index for Xi’an on 2018.09.12 [51, 53].
The peak appeared from 18:00∼19:00, and the valley, excluding late night, appeared from 13:00∼14:00.
Table 3.
Number of force merge times.
Table 4.
VISSIM simulation calibration results.
Table 5.
Operational performance of MUTI and ESUL with investigation data (valley hour).
Table 6.
Operational performance of MUTI and ESUL with investigation data (peak hour).
Table 7.
Safety performance of MUTI and ESUL with investigation data (valley hour).
Table 8.
Safety performance of MUTI and ESUL with investigation data (peak hour).
Table 9.
Parameters input into sensitivity analysis in VISSIM.
Fig 9.
Sensitivity analysis of flow 1, EW through vehicles.
The X axis is different traffic volumes, the Y axis is u-turn ratio and the Z axis is improvement ratio (Ratio = (MUTI-ESUL)/MUTI*100%) in a,b, and reduced times (Reduced times = MUTI-ESUL) in c. a. Travel time improvement ratio. b. Delay improvement ratio. c. Reduced number of stops.
Fig 10.
Sensitivity analysis of flow 2, EE U-turn vehicles.
The X axis is different traffic volumes, the Y axis is U-turn ratio and the Z axis is improvement ratio (Ratio = (MUTI-ESUL)/MUTI*100%) in a,b, and reduced times (Reduced times = MUTI-ESUL) in c. a. Travel time improvement ratio. b. Delay improvement ratio. c. Reduced number of stops.
Fig 11.
Sensitivity analysis of flow 3, WE through vehicles.
The X axis is different traffic volumes, the Y axis is U-turn ratio and the Z axis is improvement ratio (Ratio = (MUTI-ESUL)/MUTI*100%) in a,b, and reduced times (Reduced times = MUTI-ESUL) in c. a. Travel time improvement ratio. b. Delay improvement ratio. c. Reduced number of stops.
Fig 12.
Sensitivity analysis of flow 4, WW U-turn vehicles.
The X axis is different traffic volumes, the Y axis is u-turn ratio and the Z axis is improvement ratio (Ratio = (MUTI-ESUL)/MUTI*100%) in a,b, and reduced times (Reduced times = MUTI-ESUL) in c. a. Travel time improvement ratio. b. Delay improvement ratio. c. Reduced number of stops.
Fig 13.
Effectiveness of ESUL compared with MUTI. Traffic volume is 4851 veh/h and U-turn ratio is 0.12.
a.Travel time. b.Delay. c.Number of stops.