Journal of the Eastern Asia Society for Transportation Studies, Vol. 6, pp. 137 - 146, 2005
EFFECTS OF MOTORCYCLES ON TRAFFIC OPERATIONS ON ARTERIAL STREETS Terdsak RONGVIRIYAPANICH Lecturer Faculty of Engineering King Mongkut’s Institute of Technology North Bangkok 1518 Piboonsongkram Rd. Bangsue Bangkok 10800 Thailand Fax: +66-2587-4337 E-mail:
[email protected]
Charong SUPPATTRAKUL Graduate Student Faculty of Engineering King Mongkut’s Institute of Technology North Bangkok 1518 Piboonsongkram Rd. Bangsue Bangkok 10800 Thailand Fax: +66-2587-4337
Abstract: This study analyses the effects of motorcycles on traffic operations at signalized intersections and a mid-block section of an urban road. Data collection was done at two intersections, one with motorcycle queue storage and the other without. Discharge headway was used to identify the relationship between a number of motorcycles discharged in each signal cycle and the start-up lost time of passenger cars. In addition, the effectiveness of motorcycle queue storage is also examined. Start-up lost time of passenger cars is found to be linearly correlated with the number of motorcycles in the waiting queue. Motorcycle queue storage is found to increase start-up lost time of the traffic. At mid-block, Passenger Car Equivalent (PCE) of motorcycle at different traffic volume and proportion of motorcycles in traffic stream are determined. It is found that PCE of motorcycles consistently decreases with the share of motorcycle in total traffic. Key Words: Effects of motorcycles, Start-up lost time, Passenger Car Equivalent
1. BACKGROUND Operation and management of urban streets under mixed traffic is a challenging task. In Asian countries, motorcycle constitutes a considerable share of traffic in urban areas. Some researchers made attempt to quantify the effects of motorcycle especially at signalized intersections (Nguyen, 1999 and Sorasak, 2000). In Thailand, according to the statistics in 2001 the number of motorcycles registered is 15.2 million, equivalent to 70% of total vehicles in the country (Department of Land Transport, 2001). It is apparent that effects of motorcycle in these countries can not be neglected. In addition, motorcycles are also more exposed to traffic accident as shown by the traffic accident statistics of 2001 showing that 80% of traffic death in Thailand is motorcycle users (National Police Agency, 2001). Thai government realized the significance of the problem and introduced some measures segregate motorcycles from other traffic. Among implemented measures are:
• •
Prohibition of motorcycles from using expressway, flyover and major roads of the arterials with frontages Provision of exclusive motorcycle queue storage at some busy signalized intersections
Nevertheless, there exists no research directly addresses these issues, making it hard to objectively evaluate the effectiveness of these measures. This study shall investigate the effects of motorcycles at both signalized intersections and at a mid-block of urban street. The findings of this study shall be used to support decision-making in urban traffic management.
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Journal of the Eastern Asia Society for Transportation Studies, Vol. 6, pp. 137 - 146, 2005
2. OBJECTIVES
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To establish relationship between the number of motorcycles in waiting queue and start-up lost time To examine the effects of motorcycles at mid-block of urban street in terms of PCE
3. RESEARCH METHODOLOGY This study comprises two major parts. First is an investigation of effects motorcycles at signalized intersections. The other is concerned with an analysis of headway distribution of passenger cars and motorcycles at a mid-block of urban road under mixed traffic. 3.1 Study Area
(a) Prachanukul Intersection (with MC queue storage)
Wongsawang Intersection
Pong Pech Intersection
Tao Poon Intersection
Narathiwat Rd.
To Sathorn Intersection
Target Lane for Data Collection
3.50 3.20 3.20 3.20 3.20
Chah Rd.
MC
Rachadapisake Rd.
MC
3.10 2.90 2.50
Target Lane for Data Collection 15.30 10.20
Chah Rd.
The study areas are selected with consideration on the site where there is a considerable share of motorcycles in total traffic. Two signalized intersections, one with motorcycle queue storage and the other without as illustrated in Figure 1, are chosen as the study areas for the first part of the study. A mid-block section of an urban street in Bangkok is selected as the study site for the second part of the study as shown in Figure 2.
(b) Chan-Nontri Intersection (without MC queue storage)
Figure 1. Study Sites for Signalized Intersections
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Journal of the Eastern Asia Society for Transportation Studies, Vol. 6, pp. 137 - 146, 2005
Soi Wongsawang 6
Soi Wongsawang 4
Observed Point 3.10 3.20 3.10
Rama VII Bridge
Wongsawang Intersection
Figure 2. Study Site for Mid-block 3.2 Data Collection Videotaping is used a means for to collect data from the study sites. The following data are then extracted in the laboratory:
• • •
Discharge headway of passenger cars and motorcycles only at the accuracy of 0.01 sec Number of motorcycles in the waiting queue at the beginning of green phase Time headway of passenger cars and motorcycles when passing the reference point at mid-block at the accuracy of 0.01 sec
It should be noted the data item 1 and 2 are obtained from signal cycles, in which only passenger cars and motorcycles discharge from the stop line. This is to ensure that there are no other effects but that of motorcycles on the traffic operations at the signalized intersections.
4. EFFECTS OF MOTORCYCLES AT SIGNALIZED INTERSECTIONS Firstly, discharge headway of passenger cars and motorcycles from the stop line are used to determine the saturation headway and start-up lost time. For the case of Chan-Nontri intersection, data are divided into 2 groups between signal cycles in which motorcycles exist in the waiting queue and those with only passenger cars. For the case of Prachanukul intersection, data are classified into 2 groups depending on whether there are any passenger cars penetrating into the motorcycle queue storage or not. Figure 3 illustrates the four analysis cases.
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Journal of the Eastern Asia Society for Transportation Studies, Vol. 6, pp. 137 - 146, 2005
Chan-Nontri Intersection Prachanukul Intersection Case I
Case II
Case III
Case IV
MC
MC
Figure 3. Analysis Cases for the Investigation of Motorcycle Effects at Signalized Intersection
Saturation headway and start-up lost time are determined separately for each analysis case. The saturation headway is identified by performing t-test between the average discharge headway of nth vehicle and the successive vehicles. If there is no significant difference between the both values, the average discharge headway of the successive vehicles is used as the saturation headway. Start-up lost time is defined as the total additional headway consumed by the first n vehicles in the queue above and beyond the saturation headway a shown in Equation 1 (McShane et al, 1998). n
Start-up lost time = ∑ ( H i − H s )
(1)
i =1
Where Hi = Discharge headway of ith vehicle (sec) Hs = Saturation headway (sec) n = Number of vehicles discharged before saturation headway is achieved Figure 4 and Table 1 summarize the results of each case. As seen from Table 1, there is virtually no difference between the saturation headways of case 1 & 2 and those of case 3 & 4. This indicates that motorcycles do not affect the saturation headway of passenger cars. Their effects appear in the increase of start-up lost time from the average of 3.24 sec in case 1 to 5.07 sec in case 2 and from 6.12 sec in case 3 to 8.25 sec in case 4. Table 2 and 3 show that the differences between the start-up lost time of case 1 and 2 and that of case 3 and 4 are statistically significant at 95% level of confidence.
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Journal of the Eastern Asia Society for Transportation Studies, Vol. 6, pp. 137 - 146, 2005
case I case II
8 6 4 2 0
10
Headway (sec.)
Headway (sec.)
10
case III case IV
8 6 4 2 0
1
2
3
4
5
6
7
8
9
1
10
Positoin in queue
(a) Without MC queue storage cases
2
3
4
5
6
7
8
9
10
Position in queue
(b) With MC queue storage cases
Figure 4. Average Discharge Headway of Vehicles in the Waiting Queue
Table 1. Saturation Headway and Start-up Lost Time for Each Analysis Case Case 1 2 3 4
Position in queue where saturation flow begins 7th Vehicle 6th Vehicle 6th Vehicle 6th Vehicle
Saturation headway (sec) 1.88 1.89 1.94 1.93
Start-up lost time (sec) 3.24 5.07 6.12 8.25
Table 2. t-test Result between Start-up Lost Time of Chan-Nontri Intersection
Mean Variance Observations t Stat P(T
