HEADWAY DISTRIBUTION OF TRAFFIC PLATOON IN URBAN ROAD, CASE STUDY : PADANG CITY

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1 HEADWAY DISTRIBUTION OF TRAFFIC PLATOON IN URBAN ROAD, CASE STUDY : PADANG CITY Purnawan Department of Civil Engineering University of Andalas Padang purnawan@gmail.com Tian Adilla Department of Civil Engineering University of Andalas Padang askartking@yahoo.co.id Abstract Behaviours of traffic flow in urban area usually affected by component of traffic flow such as road geometric condition, vehicle type, driver characeristic and road environment. Traffic platoon could arise when traffic volume is high. Traffic volume is only one of component that trigger to produce traffic platoon. The behaviour of traffic platoon are strongly affected by driver, other factors that affect traffic platoon are traffic flow condition and traffic environments. Traffic survey has been conducted using handycam in the morning, afternoon and evening at Jl. Khatib Sulaiman, this road is relatively flat and straight with low side frictions. Traffic volume at this road is relatively high at peakhours, this condition could produce traffic platoon. From data analysis, there are four types of following vehicle, the vehicles are classified into two types, i.e : light vehicle and heavy vehicle. Traffic platoon highly occur at interval headway between 1,1-1,8 second. The distributions of headway are relatively similar for collected data in the morning, afternoon and evening. Key Word : distribution, traffic platoon, urban road INTRODUCTION Background Traffic platoon usually arise in urban areas, these cases can be found at urban road when traffic volume is high. Another location that could produce traffic platoon is a approach road of traffic signal. Traffic platoon at those two locations have different behaviours. The behaviours of traffic platoon at road section are much affected by the level of traffic of traffic volume. In high traffic, vehicle will move relatively slow and stable headway. However in low traffic volume, vehicles tend to move faster and relatively unstable headway. The speed of vehicles are strongly affected by traffic volume and driver characteristic (Pueboobpaphan, and Arem, 2010), other factors such as road condition and road environment have low contribution on the behaviours of traffic platoon. In traffic signal, traffic platoons are also affected by the fase of traffic signal, red time of signal and spacing between traffic signal (Grace and Potts, 1964; Treiterer, Nemeth and Vecello, 1973). Based on those conditions, this paper explores the behaviour of traffic platoon in urban road with relatively ideal road geometric condition. In this road, traffic platoon was assumed affected by the level of traffic volume and driver behaviour. Therefore, the behaviour of traffic platoon that affected by those factors could be easily identified. This paper explains the behaviour traffic platoon in urban area. Traffic platoon was captured using handycam in urban road. The behaviours of traffic platoon are indicated by headway distribution.

2 TRAFFIC PLATOON Traffic platoon in urban area In urban area, traffic flow usually The behaviour of traffic flow usually affected by road condition, vehicle type and condition, driver behaviour and road environment. In urban area traffic platoon could be found during peak hour. Traffic platoon usually arise because of high traffic volume. In high traffic volume, drivers usually control the headway in certain distance. It is because of the limited distance for driving. This behaviour usually does not occur along road section, side obstruction by vehicle parking, stop and go by paratransit, pedestrian crossing and would reduce vehicle speed. Therefore, traffic platoon could not occur along road section, except when congestion occur at along road section. The movement of traffic platoon will affect the efficiency of traffic movement. It is affected by the headway between vehicle (Dao, Clark and Huissoon, 2008). Sebayang (1998) identify the effect of platoon dispersion on the maximize traffic movement between traffic signal. Factors affecting traffic platoon behaviours The behaviour of traffic flow usually affected by road condition, vehicle type and condition, driver behaviour and road environment. In urban area traffic platoon could be found during peak hour. Traffic platoon usually arise because of high traffic volume. In high traffic volume, drivers usually control the headway in certain distance. It is because of the limited distance for driving. This behaviour is unique for certain location. Those headway between vehicles usually are used as the parameter to identify the behaviour of traffic platoon. Other factor that could influence the efficiency traffic platoon movement is gap between traffic platoon, this gap could will affect on saturation of traffic flow (Ramezani, Benekohal and Avrenli, 2008). Jiang, Li and Shamo (2003) investigated the behaviour traffic platoon in rural area, this study shows that there are inefficent on traffic signal operational because of low traffic volume. DATA COLLECTION AND ANALYSIS The following steps has been conducted during the research. Pilot study was carried out to find the appropriate location for survey. Preliminary survey using handycam for data collection was conducted. The location for survey has been determined. It is Jl. Khatib Sulaiman road, this road is straight and flat road without side obstruction. Traffic volume in this road is in the range of moderate to high, in this condition traffic platoon could arise. In this road, traffic platoon are relatively not affected by side friction. From the result of pilot survey, time period of survey, method of survey and completed equipment for the next survey was determined. Surveys for data collection have been conducted during peak hours, the period of survey is as follow, morning ( ), afternoon ( ) and evening ( ). In those times, high traffic volume could be found. Surveys were conducted on Monday and Tuesday, it has identified Monday usually has higher traffic volume compared by Tuesday. Handycam accompanied by tripod was used to capture the traffic flow.

3 The collected data were transferred into computer and playback using video. The case of traffic platoon were observed and analysed. Data logger software was used to capture traffic platoon data. This data is headway between vehicles within traffic platoon. Analysis data was conducted using EXCEL speadsheet. RESULTS AND DISCUSSION Distribution of Following Vehicle Data of the following vehicle behaviours are classified into 4 types. Only 2 vehicle types are determined, it is light vehicle (LV) and Heavy Vehicle (HV), bus was included as heavy vehicle and paratransit (angkot) was included as light vehicle. In this study, motor vehicles were not included, it is because of unstable following behaviour of these vehicles. The distribution of following vehicle types are shown in Figure 1 and 2. Figure 1 : Distribution of following vehicle types collected on Monday Figure 2 : Distribution of following vehicle types collected on Tuesday

4 Figure 1 shows the distribution of following vehicle that have been collected on Monday with cases, and Figure 2 shows the distribution of following vehicle that have been collected on Tuesday with cases. It is shown that the pattern of both curve are relatively similar. Different times and days of data collection did not produce diffrent results. From data collection, the following vehicle LV-LV is the highest frequency. This is indicate that traffic flow are dominated by light vehicle (LV). Distribution of Headway Headway distributions of following vehicle are shown in Figure 3 and 4. These figures show the distribution of following vehicle that have been collected on Monday, and Figure 2 shows the distribution of following vehicle that have been collected on Tuesday. It is shown that the pattern of both distribution are relatively similar, the high fequency headway occur at interval 1,10-1,80 seconds. The difference of those distibutions are on the frequency of headway. Figure 3 : Distribution of Traffic Platoon Headway Collected on Monday Figure 4 : Distribution of Traffic Platoon Headway Collected on Tuesday

5 From Figure 4 and 5 are shown that the effect of data collection time does not affect the different pattern of headway distribution. Therefore, it is concluded that the behaviours of traffic platoon are not affected time. Cumulative Distribution of Headway Figure 5 and 6 shows the cumulative distributions of headway, data in Figure 5 was collected on Monday and data in Figure 6 was collected on Tuesday. Figure 5 : Cumulatif Distribution of Traffic Platoon Headway collected on Monday Figure 6 : Cumulatif Distribution of Traffic Platoon Headway collected on Tuesday

6 In Figure 5 and 6 there are shown that at 85% percentile, the interval headway collected on Monday are between 4,50 and 5,00, and collected data on Tuesday are between 4,00 and 5,00. This can be concluded that traffic platoon in urban area mostly occur at headway less than 5 seconds. CONCLUSION Based on survey in urban area, the highest frequency of following type of vehicle in traffic platoon are Light Vehicle - Light Vehicle (LV - LV). This indicate that most people in urban area travel using car, because the number of paratransits that include in traffic platoon are limited. During following vehicle, headway in the range of seconds are highly used by driver within traffic platoon. The effect of time and day on survey period does not produce different pattern of headway distribution. Cumulatif distributions of headway show the major behaviour of driver following. It is shown that driver following in traffic platoon using headway less than 5 second. This percentage is indicated at the peak transition of the curve. REFERENCES Dao,T.S, Clark, C.M and Huissoon, J.P, 2008, Distributed Platoon Assignment and Lane Selection for Traffic Flow Optimization, Proceeding of IEEE Intelligent Vehicles Symposium Eindhoven University of Technology Eindhoven, The Netherlands, June 4-6, 2008 Grace, M.J and Potts, R.B, 1964, A Theory of The Diffusion of Traffic Platoons, Operation Research March/April Vol.12 No.2, pp Jiang, Y, Li, S and Shamo, D.E, 2003, Development of Vehicle Platoon Distribution Models and Simulation of Platoon Movements on Indiana Rural Corridors, JTRP Technical Report, Indiana Department of Transportation and Purdue University, West Lafayette, Indiana. Pueboobpaphan, A and Arem, B.V, Driver and Vehicle Characteristic and Platoon and Traffic Flow Stability. Transportation Reseach Record : Journal of the Transportation Research Board Vol.2189, pp Ramezani, H, Benekohal, R.F, Avrenli, K.A, 2008, Statistical distribution for inter platoon gaps, intra platoon headways and platoon size using field data from highway bottleneck, TRB Traffic Flow Theory Committee (TFTC) Summer Meeting and Greenshields Symposium, July 2008, USA. Sebayang, N, 1998, Model Development of Performance Analysis for Signal Coordination on A Two Way Street, MSc Thesis,s Department of Civil Engineering, Institute Technology of Bandung. Treiterer, J, Nemeth, Z and Vecello, R, 1973, Effect of Signal Spacing on Platoon Dispersion, The Ohio State University Columbus, Ohio, USA.