A COMPARATIVE STUDY OF EFFECT OF MOTORCYCLE VOLUME ON CAPACITY OF FOUR LANE URBAN ROADS IN INDIA AND THAILAND Sanjeev SINHA * Associate Professor Department of Civil Engineering National Institute of Technology Patna Patna 800 005, India Phone: +91 612 2341613 Fax: + 91 612 270631 Email: sanjeev_bangkok@yahoo.com * Corresponding Author Pichai TANEERANANON Professor Center for Road Safety Research Department of Civil Engineering Prince of Songkla University Hat Yai 90112, Thailand Phone: +6674212499, +6674287141 Fax: +6674446519 Email: breathislife@yahoo.com Satish CHANDRA Professor Department of Civil Engineering Indian Institute of Technology Roorkee Roorkee 247 667 Uttarakhand, India Phone: +91 1332 285468 Email: satisfce@iitr.ernet.in ABSTRACT: Highway Capacity Manual (HCM) of USA provides techniques for evaluation of capacity and quality of service of any facility. Studies have shown that these techniques have limited application for heterogeneous traffic situation prevailing in the developing world. As motorcycles are found in large numbers on the urban roads of developing countries; the present study is an attempt to determine their effect of on the capacity of four lane urban roads. A comparative study was carried out in Thailand and India, where speed-volume relationship was used for capacity estimation. It was found that similar to the finding of a study carried out in India, the capacity of four lane urban roads in Thailand increases with the increase in percentage of motorcycle in the traffic stream. However, though the estimate of capacity was very close to that recommended by the Indonesian highway capacity manual, it was different from the estimated values for similar traffic situation in India. KEYWORDS: Capacity, motorcycle, speed-volume relationship 52
A Comparative Study of Effect of Motorcycle Volume on Capacity of Four Lane Urban Roads in India and Thailand 1. INTRODUCTION Capacity of a facility is the maximum hourly rate at which persons or vehicles can be expected to traverse a point or a uniform section of a lane or roadway during a given time period under the prevailing roadway, traffic and control conditions (HCM, 2000). HCM provides a system of techniques for the evaluation of capacity and quality of service of any facility. The factors affecting capacity are roadway, traffic and control conditions and their deviations from the specified standard conditions known as base conditions. The techniques hold good for prevailing traffic conditions in USA and other developed countries. However for developing countries in South-East and South Asia, it has limited application as the traffic nature is heterogeneous in these countries. Large numbers of motorcycles ply on the urban roads of developing world and Thailand as well as India being no exception to it. The objective of the paper is to analyze the effect of motorcycle volume on the capacity of four lane urban roads using speed-volume relationship and to compare its effect in India and Thailand. Four lane divided urban roads are very common in urban areas of developing countries. These are the roads with two-lanes in each direction and the traffic flow in two directions separated by a median. Indonesian Highway Capacity Manual (IHCM) (1993) has defined standard road of this category as those having 14 meter carriageway width, 50-50 directional distribution, low side friction, straight alignment, kerbed and at level terrain. 2. LITERATURE REVIEW Ramanayya (1988) has observed that US highway capacity manual (HCM), which is an authoritative document on capacity analysis, has 53 limited application for heterogeneous traffic condition prevailing in India. He developed a computer simulation model for depicting road traffic behavior under mixed traffic condition. Chandra and Vishnu Prasad (2006) while analyzing the capacity of multilane divided roads in India under mixed traffic have observed that capacity increases with the proportion of 2 wheelers in the traffic stream. Chandra and Sinha (2001) have found that capacity of two lane roads in India reduces as the directional split moves away from 50/50. They also observed that the capacity decreases as the proportion of slowmoving vehicles in traffic stream increases. Bang et al. (1994) in their study in Indonesia concluded that capacity manuals cannot be applied in Indonesia due to large difference in driver behavior, traffic composition and level of road-side activities. They observed that for two lane roads free-flow speed of vehicles in Indonesia was less than that in developed countries due less road width and side friction. Further the capacity of two lane two way road was slightly higher than in developed countries. IHCM (1993) suggests that for four lane two way urban road base capacity is 5700 pcu/hr. HCM (2000) establishes that for multilane highway capacity varies with free flow speed. It gives the values of capacity as 2200, 2100, 2000 and 1900 pcu/hr/lane for free flow speeds of 100, 90, 80 and 70 km/hr respectively. Sarna et al. (1989) and Taylor et al. (1990) have recommended the use of video technique for speed and headway data acquisition. 3. DATA COLLECTION A video based photographic technique was used for data collection. The technique has the advantage of lesser requirement of manpower. The data collection does not interfere with the traffic movement and the storage of data is permanent. The locations of data collection were
straight and level mid-block sections away from intersections. Six identical four lane divided road sections with shoulders on either side were selected in the Songkhla Province of Thailand and ten locations were in India (Chandra and Vishnu Prasad, 2006). The locations in Thailand as shown in Figure 1 are as follows: I Hatyai Technical College to Songklagarind Hospital (19 th Sept 2010, 13.00 to 1800 hrs) II Hatyai Technical College to Hatyai (19 th Sept 2010, 13.00 to 1800 hrs) III Klongrain Market to Songkhla (17 th Sept 2010, 13.00 to 1800 hrs) IV Klongrain Market to Songklangarind Hospital (17 th Sept 2010, 13.00 to 1800 hrs) V Songkhlanagarind Hospital to Klongrain Market (16 th Sept 2010, 13.00 to 1800 hrs) VI Songkhlanagarind Hospital to Hatyai Tech College (16 th Sept 2010, 13.00 to 1800 hrs) HATYAI TECHNICAL COLLEGE SONGKLANAGARIND HOSPITAL KLONGRAIN MARKET Figure 1 Locations of points for data collection In order to find out the speed and volume, a video camera was placed on a vantage location so that a longitudinal trap of 30 meters is focused. The data was collected for about four hours on each section on a typical clear weekday. The recorded video was later played on a 54
Implication of Public Transport Services To Rural Mobility computer and the desired information was extracted. To make the analysis more meaningful, the vehicles of similar characteristics were grouped together. Altogether 11 categories of vehicles were identified and thus classified volume count was performed. The identified categories of the vehicles are the same as adopted by Traffic Master Plan Study of Songkhla Province done by the Office of Transport and Traffic Policy and Planning (OTP; 2009) This was done through classified 5- minute count for all vehicles passing through the observation point. The speed measurement was done by measuring the time taken by each category of vehicle to cover the trap length. The time was recorded using a stopwatch to the accuracy of 0.1 seconds. As mentioned above, 11 categories of vehicles were identified in the traffic stream in Songkhla Province in Thailand. In order to estimate the traffic volume and capacity under such heterogeneous traffic condition, different categories of vehicles are converted into a common unit called passenger car units (PCUs). PCUs are based on the static and dynamic characteristics of the vehicles the most important being the mean speeds and their projected rectangular areas. The different categories of vehicles along with their PCU values as adopted in the present study are given in Table 1. In a separate study conducted by Chandra and Prasad (2006) in India, 7 categories of vehicles were identified and their PCU values were calculated based on the speeds of vehicles and their projected areas. They used dynamic PCU at different sections as given in Table 2. In mixed traffic situation, weighted space mean speed is used for the present study, where speed of each category of vehicle is calculated by measuring the time to cross the trap length. The weighted mean stream speed is then calculated using Equation 1. v m = k i 1 k i 1 nivi ni (1) where, k = total number of vehicle categories present in the stream v m = Weighted mean stream speed (km/hr) v i = Speed of vehicle i n i = Number of vehicles of category i Table 1 Categories of vehicle with PCU in Thailand (OTP, 2009) Serial No. Category of vehicles PCU 1 Passenger cars 1 2 Motorcycles 1/3 3 Van 1 4 Tuk-tuk 1 5 Pickup 1 6 Bus 2 7 Mini bus 1.5 8 6 wheeled truck 1.5 9 10 wheeled truck 2 10 Semi Trailers 3 11 Trailers 4 55
Section Table 2 PCU Values of Vehicles at Different Sections in India Motor Three Tractor Pedal Cycle Truck Cycles Wheeler Trailer Cycle Rickshaw I 0.151 0.610 4.655 4.457 0.358 1.797 II 0.214 0.811 4.479 6.011 0.353 1.357 III 0.192 0.758 5.127 5.607 0.423 1.493 IV 0.189 0.720 5.091 4.885 0.350 1.607 V 0.229 1.097 5.971 * 0.433 1.804 VI 0.222 1.007 5.162 4.976 0.309 1.072 VII 0.229 0.987 5.009 6.659 0.397 0.547 VIII 0.211 0.653 2.750 8.889 0.454 0.939 IX 0.199 0.825 5.614 * 0.388 1.407 X 0.182 0.722 5.730 * 0.314 1.232 *This category of vehicle was not present at the time of data collection 4. CAPACITY ESTIMATION The capacity estimation was done by the use of speed-volume relationship, which is the most fundamental and reliable method. This method is based on actual field data collection. In this method the speed-volume data are plotted with speed on the ordinate and volume on the abscissa. The scatter plot is shown in Figure 2. As may be seen, the data do not indicate any specific trend. It is because of the low range of traffic volume and speed which was captured during limited duration of field observations. Therefore, the enveloping curve technique was used to draw the speed flow diagram. In this method, eyeballed curve is drawn encompassing all the data points (Refer Figures 2 and 3). The basic concept of this method is that the capacity is always larger than actual flow observed at site and therefore speed flow curve should envelop all the data points. The speed-volume relationships are obtained for all the locations in Thailand and these are used to find the capacity and free flow speeds. The estimates of capacity, free flow speed and percentage of motorcycles in the traffic streams are summarized in Table 3. 56
Implication of Public Transport Services To Rural Mobility Seri al No. Table 3 Capacity and free flow speed in Thailand Location Capacity (pcu/hr) Percentage of motorcycle in traffic stream Free flow speed of the traffic stream (km/hr) 1. Hatyai Technical College ( to Songklagarind 2860 30.03 105 Hosp.) 2. Hatyai Technical College ( to Hatyai) 2810 28.01 101 3. Klongrain Market ( to Songkhla) 2975 29.85 110 4. Klongrain Market (to Songlagarind Hosp.) 2930 29.30 105 5. Songklanagarind Hospital (to Klongrain Market) 6. Songklanagarind Hospital (to Hatyai Tech College) 3010 30.14 100 2950 28.93 101 Similarly, speed-volume relationships were obtained in India by Chandra and Vishnu Prasad (2006) for the ten locations in India by drawing eyeball curve through data points and the results are summarized in Table 4. 120 100 80 Speed (km/hr) 60 40 20 0 0 500 1000 1500 2000 2500 3000 3500 Volume (PCU/hr) Figure 2 Speed-volume relationship at Hatyai Technical College (Towards Songklanagarind Hospital) 57
100 80 Spped (km/hr) 60 40 20 0 0 500 1000 1500 2000 2500 3000 3500 Volume (PCU/hr) Figure 3 Speed-volume relationship at Hatyai Technical College (Towards Hatyai) Table 4 Capacity and Free Flow Speed at Different Sections in India Section Capacity Percentage of Free Flow Speed (pcu/hr) two-wheelers (km/h) I 2239 41.97 36.72 II 2433 46.87 38.92 III 2653 41.97 40.33 IV 2750 54.50 38.5 V 3018 67.77 51.77 VI 2883 57.64 53.05 VII 2769 55.73 42.09 VIII 2411 29.84 48.22 IX 2748 37.39 47.26 X 2321 29.38 33.43 58
Implication of Public Transport Services To Rural Mobility 5. DISCUSSION The speed-volume relationships were used for finding out capacity of four lanes divided urban roads at identified locations. The methodology involved is estimating capacity for two lane roads in each direction using the diagram and adding them to get the capacity. Tables 3 and 4 show that there is increase in the capacity with the increase in the percent of motorcycle in the traffic stream, though the locations where data collection was done, do not have much variation in the composition of traffic stream. The free flow speed remains almost constant. The variation in capacity with the percent of motorcycle in the traffic stream is shown in Figure 4. With the given set of data, linear regression analysis was carried and the variation in capacity with the percent of motorcycles is given by the Equation 2. C = 1219.5 + 57.9*M (2) R 2 = 0.39 where, C = Capacity (pcu/hr) M = Percentage of motorcycle in traffic stream Though the data collected has a narrow range of variation in the percentage of motorcycles, it gives the idea of the trend of increase in the capacity with the increase in the percentage of motorcycles in the traffic stream. The effect of motorcycle traffic on capacity in India is shown in Figure 5 (Chandra and Prasad, 2006). The relationship between capacity and percentage of motorcycles is given in Equation (3). C = 1880 + 16.02*M (3) R 2 = 0.60 Using Equations 2 and 3 the capacity at different percentages of motorcycles in the traffic stream is given in Table 5 for Thailand and India. It can be seen from the equations that the capacity increases with the increase in percentage of motorcycles in the traffic stream. This may be attributed to due to lesser longitudinal and lateral gaps maintained by motorcycles in the traffic stream as compared to the large sized vehicles. Table 5 however, shows that the capacity estimates for both the countries for same percentage of motorcycles are different. It is attributed to high free flow speed on Thailand roads as compared to roads in India. Table 5 Variation of capacity with percentage of motorcycles Serial No. Percentage of motorcycles in traffic stream Capacity in Thailand (pcu/hr) Capacity in India (pcu/hr) 1. 25 2669 2282 2. 26 2727 2299 3. 27 2785 2316 4. 28 2843 2334 5. 29 2901 2351 6. 30 2959 2368 7. 31 3017 2385 8. 32 3075 2402 59
Figure 4 Effect of motorcycles on capacity in Thailand. Table 3 indicates that there is only a small variation in the percent of motorcycle volume (28.01 to 30.14 %) in the traffic stream, whereas large variations in the capacity (2810 to 3010 pcu/hr) have been observed. This may be due to inherent driver behavior in Thailand. This has resulted in higher scatter of data points and hence lower value of R 2. Figure 5 Effect of motorcycles on capacity in India 60
Implication of Public Transport Services To Rural Mobility 6. CONCLUSIONS AND RECOMMENDATIONS The capacity of four lane divided urban roads in Thailand is very similar to that recommended in the Indonesian Highway Capacity Manual which is 5700 vehicles/hr for the base condition. This is due to similar traffic conditions exiting in the developing countries of South East Asia but different from those observed in developed world. In Indian case also the capacity is observed to be similar. However, free speeds in Thailand are much higher than those in India. It reflects on better road surface conditions in Thailand. There is an increase in the capacity of four lane divided urban roads on account of increase in the percentage of motorcycles in the traffic stream. The increase in capacity can be quantified using Equation 2 and 3 which are linear in nature. However, these equations need further validation for good range of percentage of motorcycles. Thus, there is a need to collect more speedvolume data with large variations in the percentage of motorcycles on Thai roads. The present study is certainly one step towards development of capacity manual for developing countries like Thailand, India, Vietnam and other countries of the region which do not have the capacity manuals of their own, for the evaluation of quality of service and capacity analysis of highway and street facilities. In order to arrive at an unambiguous and concrete conclusion, more data sets shall be required. Thus, more locations need to be identified, which should provide much variation in percentage of motorcycles and also in the speeds of vehicles which will make the drawing speed-volume diagram easier. Further, the dynamic PCU factor should be developed for converting heterogeneous traffic in to a homogenous equivalent instead of using fixed values as taken in the present study. ACKNOWLEDGEMENT The authors like to express their sincere thanks to Borpit Klinrussamee and other students and staff members of Thailand Accident Center, for their effort in data collection for the present study. REFERENCES Bang, K.L., Carlsson, A. and Palgunadi (1995) Development of speed flow relationship for Indonesian rural roads using empirical data and simulation, Transportation Research Record 1484, Transportation Research Board, Washington D.C. Botma H. (1988) Effect of traffic operation of a slow moving vehicle on two lane rural roads, Proceedings 14 th ARRB Conference, Part 2, Canberra, pp. 48-55 Chandra, S. and Sinha, S.(2001) Effect of directional split and slow-moving vehicles on two lane capacity. Road and Transport Research, Vol. 10, No. 4, ARRB Transport Ltd, Victoria, Australia 61
Chandra, S. and Prasad, Vishnu N. (2006) Capacity of Multilane Divided Urban Roads Under Mixed Traffic Conditions, Highway Research Bulletin 75, Indian Roads Congress, New Delhi, pp.97-103 Highway Capacity Manual (2000) Transportation Research Board, Special Report 209, Washington D.C. USA Indonesian Highway Capacity Manual (IHCM) (1993) Directorate General of Highways, Ministry of Public Works, Jakarta, Indonesia Ramanayya, T.V. (1988) Highway capacity under mixed traffic conditions, Traffic Engineering and Control, 29(5), United Kingdom, pp. 284-300 Office of Transport and Traffic Policy and Planning (OTP) (2009) Traffic Master Plan Study for Songkhla Province, Final Report Sarna, A.C., Jain, P.K. and Chandra, G. (1989), Capacity of Urban Roads A Case Study of Delhi and Bombay, Highway Research Bulletin 40, Indian Roads Congress, New Delhi, pp 38-49 Taylor, M.A.P., Young, W. and Thompson, R.G. (1990) Headway and speed data acquisition using video, Transportation Research Record 1225, Transportation Research Board, Washington D.C. 62