Simulation of traffic flow in unsignalization intersection using computer software SIDRA in Baghdad city

. Computer simulation is a vital means for the examination of expressways and urban lanes and streets. Transportation experts concentrate on the arrangement and dissemination of traffic jams on roadways. The objective of this study is to calculate and analyses the travel time, delay time, degree of saturation, and level of service and travel speed in Jordan intersection in Baghdad, Iraq using Sidra software. The number of vehicles passing Jordan intersection was recorded by the author of this work from 7am to 3pm for four days. A simulation model has been used to assess the performance of the current intersection. Results demonstrated that the level of service (LOS) for Jordan intersection is D with (35 sec/veh) average delay and degree of saturation (0.996 v/c). It was concluded that Jordan intersection needs further developments like using intelligent transportation system application (ITS) to regulate traffic signals, whereby reducing traffic jam, using closed circuit TV (CCTV) might assist traffic office in identifying jam point to reduce traffic jam.


Introduction
Traffic jam happens when a volume of Traffic produces demand for more space as compared to the accessible street limit; this point is generally expressed as the degree of saturation.There are various particular circumstances that cause traffic jams; the vast majority of them decrease the limit of a street at a given point or over a specific length.Around half of U.S. traffic jam is repeating [2], and is ascribed to sheer weight of traffic; a major of the other half is attributed to the movement to traffic Ali used SIDRA software to assess the traffic flow in Roundabout and intersection in Bandar Baru Bangi [2], Al-Mimany, used Sidra to analyze and assess the traffic network in Kirkuk city [3].Ibrahim investigated the assessment of Models for roundabout capacity and performance estimation for using SIDRA, ARCADY, RODEL, SYNCHRO models and Highway Capacity Manual model (HCM 2010) to carry out the analyses [4].Examined the evaluation and enhancement of traffic operation for Al-Zeoat Intersection in Al-Ramadi city, using SIDRA traffic program [5].investigated the urban street network in kut city, using geometrics techniques like (GPS, GIS) for detecting the traffic flow patterns of the selected network [6].HCM (Highway Capacity Manual), HCS and SYNCHRO 6 computer program for operational analysis of Wadi-Saqra signalized intersection in Amman [7].used aaSIDRA computer Software to Optimize the Traffic Flow in Bandar Baru Bangi Roundabout and intersection in Selangor, Malaysia [9].
The Jordan intersection in Baghdad city, which connects Al-Mansour quarter and Hay Al -Jameeah quarter could be described as the busiest intersection with the maximum traffic jams intersections in Baghdad connects the most vital areas in Baghdad nearby 14th Ramdhan intersection which is a commercial district having numerous shopping centers, governmental facilities like passports office, Iraqi citizenship office, and traffic office.Therefore, it encounters massive jams in the day.Besides, Jordan intersection is linked with Al-Nessor roundabout which is a congested area.

Data collection
Data has been collected from the field using a video camera with high storage capacity (80 GB) and a longlife battery (battery charging lasts for 10 hours).This camera has been installed on the alrashed bank building.a good vantage points for collecting data.The time of recording started from off-peak (7:00 AM) till another off-peak (3:00 PM) and was evaluated every 15 minutes during two periods the day which is (7am-12pm) and (12pm-3pm).Table1: shows the traffic volume data expressed by a number of cars for all direction, Table1 shows the input worksheet required for analysis of the existing geometric, traffic, and signalized conditions so this data was conducted over three days.Fig 1and 2 shows the existing peak traffic flow determined by SIDRA computer program.
SIDRA computer software has been created by the Australian Road Research Board (ARRB), Transport Research Ltd., as a guide for outline and assessment of crossing points, for example, signalized convergences, roundabouts, two-way stop control, and caution sign control crossing points [10,11,12].In assessing and comparing behavior of roundabouts, there are a few advantages that the SIDRA model has over some other programming model; it gives solid appraisals of geometric delays and related breakdown impacts for the different crossing point sorts.This property of the software is essential to the computation of new options for the intersection treatments consistently.

Existing LOS at Jordan intersection
Level of Service (LOS) Method is described based on the US Highway Capacity Manual (HCM) a subjective measure used to relate the efficiency of traffic flow.LOS is utilized to dissect highway by sorting traffic flow and doling out quality levels of movement in view of execution measure like speed, density [Highway Capacity Manual HCM, 2010].LOS definitions based on delay HCM (for vehicles) is indicated in Table 6.
Existing LOS was investigated in this study using Computer Simulation Sidra Software.Results illustrated that Jordan Street LOS is (A) while the Yarmouk Road LOS is (E).However, Baghdad Tower LOS of the intersection is (D) as shown in Fig. 6, hence it is might be described as unstable flow.Speed is adversely correlated with traffic flow.Average delay is computed using SIDRA software and is related with LOS as given in

Average delay
The average delay is a crucial factor in forecasting travel time.Results for the delay is indicated in Fig. 8 which shows that both Jordan Street and Yarmouk Street have two colours red and green, red refers to LOS F and green refers to LOS A which has the minimum delay.Delay is adversely related to LOS when the delay is minimized LOS is enhanced [Turley, 2007].Whilst, Baghdad Tower Road has two colours orange and green, green refers to LOS A and orange refers to LOS E. Relation between average delay and follow up headway is illustrated in Fig. 9, It is obvious to note that the follow up heady increase with the increase of average delay.Total delay for Jordan intersection was recorded as 35.4 sec

Degree of saturation
The level of saturation (%) is a proportion of demand to limit on each lane to deal with the intersection, with an estimation of 100% implying that demand and limit are equivalent and no further movement can advance through the intersection.Values more than 85% are normally viewed as torment from movement clog, with lines of vehicles starting to shape.according to colour code based on a degree of saturation.Each degree has a specific colour.Results for the degree of saturation is clarified in Fig. 10. Green colour refers to less than 0.6 degrees of saturation, it was observed that Al Yarmouk Street has pink colour means that degree of saturation approach (0.8-0.9), whilst Baghdad Tower road has an orange colour, which refers to (0.9-1) degree of saturation.A relation between Degrees of Saturation and follow up headway is illustrated in Fig. 11.The degree of saturation for Jordan intersection is 0.996 v/c

Table 1 .
Traffic Volume at Jordan Intersection for all Approaches each Quarter Hour.

Table 3 .
Traffic Volume At Jordan Intersection For All Approaches Each Half Hour street was 444 cars at 1:30 pm.The number of cars passing Baghdad Tower at 8:00 am was 1,439 cars, whilst in 1:30 pm were recorded as 529 cars as shown in

Table 3 .
The percentage of cars passing the intersection each half an hour was calculated from Table3by dividing the total number of cars passing Yarmouk Street, Baghdad Tower and Jordan intersection during half an hour by the total number of cars shown in Table3to arrive at the percentage of cars passing

Table 4 .
Traffic percentage volume at Jordan intersection for all approaches for each in half an hour were as high as 36% at 3:00 pm.However, the percentage at Yarmouk Street was significantly different as the highest percentage was recorded at 11:00 am with 36% and 35% at 1:00 pm.The percentage of cars passing Baghdad Tower was 42% at 11:30 am and 40% at 1:30 pm and 2:30 pm as shown in

Table 4 .
The percentage of vehicle passing the intersection each half hour for 8 hours is indicated in Fig.5

Table 5 .
PHF values for Jordan intersection approaches

Table 6 .
Results of the analysis by SIDRA