Formation of Dilemma Zone at Signalised
Intersections
G S Walia1, Shahzad Ali2 and Rishi Agarwal3
Dilemma zones are the zones of confusion which are formed at an intersection during the yellow interval of traffic light when the driver approaching a signalized intersection, mayfind himself confuse as he can be close To analyze this, countdown timers were installed at major intersections of Delhi. Two approaches of a signalized intersection one with countdown timer and other without it have been studied for the present study. Result revealed that Green Signal Countdown Timer (GSCT) encouraged the drivers to pass the stop line in amber time and thus making better use of the intersection. It also eliminates the dilemma zone by making a driver to make decision in advance and also reduces red light violations.
ISSN 2455-7714, www.trpubonline.com Vol. 1, No. 3, October 2016 © 2016, www.trpubonline.com. All Rights Reserved
1 Head of Department, Department of Civil Engineering,Tula's Institute, Dehradun. 2 Student, final year,Department of Civil Engineering,Tula's Institute, Dehradun. 3 Student, final year, Department of Civil Engineering,Tula's Institute, Dehradun.
Introduction
Dilemma zone is an area in which a driver can neither stop safely nor go through the intersection before the signal turns red when presented with yellow interval at signalized intersection. During this decision making process two types of accidents are reported - rear end collision and side crashes. The dilemma zones are of two types:
1. Type 1 dilemma zone 2. Type 2 dilemma zone
Keywords: Green SignalCountdown Timer (GSCT), Dilemma Zone, Red light Violation, Xs = minimum stopping distance, Xc = maximum crossing distance, Vo = vehicle approach speed, T = reaction Time, L = length of intersection, 3w = Three-wheeler, 2w = Two wheeler, BS = Bus, BCAR = Big car.
1. Type-I Dilemma zone:- In this type of dilemma zone the distance cover by the driver at the time of confusion is calculated,this gives the value in meter. This value is different for different class of vehicle.
It is calculated by following formula:-Dilemma zone Type I = Xs-Xc[1] ...(1.1) Where: - Xs is minimum stopping distance which is given by:
Xs=VoT+Vo2/2A
Int. J. Civil Engg. Conc.Structs 2016 N Parvez et al., 2016
In which Vo is vehicle approach speed (m/s)
T is reaction time(s)
A1 is maximum deceleration (m/s2) Xc is maximum crossing distance which is given
by:-Xc= VoY+(1/2)a2 (Y-T)2-L-W[1] ...(1.3) In which Vo is vehicle approach speed (m/s)
Y is duration of yellow interval (sec) A2 is maximum acceleration (m/s2) T is reaction time(s)
L is length of vehicle (m) W is intersection width (m)
Conditions:-i. If Xs>Xc - dilemma zone is created. ii. If Xs<Xc - dilemma zone is not
created.
iii. If Xs=Xc -dilemma zone is not created
2 . Type 2 Dilemma Zone
In this dilemma zone the time taken by the driver in confusion is calculated, it is generally come as 3 to 5 sec.It is calculated by time between 10 to 90 percentile of graph plotted between time to stop line and frequency of vehicle.
II. Literature Review
Yan etal.Proposed a pavement marking with word message signal ahead that is placed on the pavement upstream of a signalized intersection. The researchers evaluated its effectiveness basedon a driving
experiment. The experiment results indicated that the marking can reduce the probabilities of both conservative-stop andrisky-go decisions, and result in a lower deceleration rate for stoppingdrivers at higher speed limit intersections.
Petet et al.Studied that the two types of dilemma zones are essential for good traffic control and safety. Type 1 dilemma zones are addressed by the selection of appropriate yellow change and red clearance intervals. Type 2 dilemma zones are addressed by the proper design of the detection system and appropriate selection of controller timing parameters.
Tang et al. studied the impact of Flash Green on dilemma zone behavior at signalized intersection with insufficient yellow interval and concluded that Flashing green significantly reduced the aof Type I DZ at the onset of yellow, while enlarged the areas of option zone and Type II DZ. Time to stop line at the onset of flashing green positively affected the stopping probability. Flashinggreen induced conservative stops by 30%, while encouraged aggressive passes slightly.
Ghosh et al. studied the effect of countdown timer on the approach speed at signalized intersection and concluded that in India countdown timers are being installed at different intersections without any engineering studies related to their impact on intersection safety and efficiency. During the last five seconds of green and amber time, higher percentage of cars and two wheelers were found to be violating the speed limit in the presence and absence of timers respectively.
Gazi et al. studied about the yellow interval dilemma zone and concluded that it is important to provide an inter green interval sufficiently long enough for drivers approaching an intersection in order to eliminate, or mitigate, the yellow interval dilemma. There are two solutions to the problem.One way is to mitigate the reinterpreting thetraffic rules as suggested by the 1992 Uniform Vehicle Code, but this can lead to some troubles. The other way is to set a long enough yellow duration (or, equivalently, the duration of a yellow interval plus a following red clearance in the new convention), and this need some observation and proper enforcement.
Selection of Site
Observations were made on intersection at Lodhi Road in Delhi. A camera was utilized for this and then the output from them was synchronized. Four traps of 10 m length were marked from stop line to the upstream side for the selected approaches. Once, the data collection was over, necessary information were extracted from the synchronized video. The intersection was left channelized nad it was free from any nearby bus stops, roadside parking and have split phase for each approach.
Basic Key Equipment
A high resolution camera was fixed at the tripod stand at the intersection for recording the traffic flow. Measuring tapes were used for measuring the speed traps and then output from the video was synchronized using a media player and calculations were done on Microsoft- Excel.
Procedure
An intersection was selected in Delhi and data was recorded during the peak hour flow of traffic.
Speed traps of 10 m length were made. In this intersection, study was conduct to find the dilemma zone Type I and Type II .To know this firstly data is collected by the help of camera which record the video of that intersection at peak hours and at the time when camera is start the speed trap is formed by measuring distance manually at the road which is generally made at 10 meter distance. This trap help to measuring the speed of vehicle which is necessary in the analysis of dilemma zone .After recoded the video for specific time the video is analysis in the computer in which analysis of vehicle speed is done. The analysis done only 15 second before the red is started.
Calculation
1. The observations were taken at the Lodhi Road Intersection at New Delhi on 20 January 2014. There were 183 vehicles out of which 101 were cars and the rest includes two-wheelers, three wheelers and buses. Data of
intersection:-Table 1: No. of Vehicles of Different Classes Crossing the Intersection
Car 2w 3w BCAR BS Total
No.of 101 23 30 22 7 183
vehicle
Total number of cycle = 40 Width of intersection = 35 meter
85 percentile value of acceleration for all vehicle = 2.02m/s2 for car = 1.86m/s2
Int. J. Civil Engg. Conc.Structs 2016 N Parvez et al., 2016
85 percentile value of deceleration for all vehicle = 3.32m/s2 and for car = 2.73m/s2
Total reaction time = 1.14 s Amber time = 5 s
Table 2 : Average Length of Vehicles for Different Classes
Car 2w 3w BS All vehicle
Average
length(m) 3.72 1.87 3.2 4.48 3.47
Calculation
1. Dilemma zone type I
i. All vehicles Xs = VoT+Vo2/2a1 (1.2) Xc = VoY+0.5a2(Y-T)2-L-W(1.3) Where: -Vo = 14.67m/s, a2 = 2.02m/s2 T = 1.14s, Y = 5s , a 1 = 3.32m/s2 L = 3.47, W = 35m. By usingequation (1.2) and (1.3), Xc = 49.93m and Xs = 49.13m Dilemma zone = (Xs-Xc )= -0.79m ii. Car Where: -Vo = 17m/s, a1 = 2.73m/s2 T = 1.14s,Y =5s,a 2 = 1.86m/s2,L = 3.72m,W = 35m.
By using equation (1.2) and (1.3), Xs = 72.31m and Xc = 60.13m
Dilemma zone = (Xs-Xc)= 12.18m
2. Type II dilemma zone
All vehicles
Table 3:Type II dilemma zone
Figure 1: Graph Between Time to Stop Line & Cumulative Frequency of Vehicles
Time in Seconds Cumulative Percentage
2 0 2.4 8.3333 2.8 8.3333 3.2 8.3333 3.6 8.3333 4 16.6667 4.4 41.6667 4.8 58.33333 5.2 91.6667 5.6 91.6667 6 91.6667 6.4 100 Value at 10 percentile = 3.68s Value at 90 percentile = 5.16s
Therefore Type II dilemma zone = 3.68s to 5.16
Result
As per the analysis show the result of creating the dilemma zone at the intersection. The type I dilemma zone at intersection for all vehicle is in negative which show that no creation of dilemma zone and for car it is in positive which show the creation of dilemma zone. Type IIdilemma zone is only for all
vehicle and not created for car, because of less data of cars.The study conclude the creation of dilemma zone at intersection which is created only at the high speed intersection and in case of low speed intersection there is no need to worry about dilemma zone .Study of dilemma zone help to control the accidental rate.
References
1. Hakkert A S and Mahalel D (1978), “Effect of Traffic Signals on Road Accidents-With Special Reference to Introduction of a Blinking Green Phase”.
2. Hurwitz D S, Knodler M A and Nyquist, B (2011), Evaluation of Driver Behavior in Type II Dilemma zones at High-Speed Signalized Intersections “The Problem of the Amber Signal Light in Traffic Flow."
3. Jeevitha Devalla’ Sabyasachi Biswas, Indrajit Ghosh-“The Effect of Countdown Timer on the Approach Speed at Signalized Intersections". 4. Tang k et al Dilemma- “Impacts of
Flashing Green on Dilemma Zone Behavior at High-Speed Intersections: Empirical Study in China”.
5. The Dilemma with Dilemma Zones"-Tom Urbanik, Professorthe University of TennesseeandPeter Koonce, Associate Engineer Kittelson and Associates. 6. Wanjing Ma1_ Yue Liu2_ and
Xiaoguang Yang3- “Investigatng Thimpacts of Green Signal Countdown Devices Empirical Approach and Case Study in China”.
