156｜Practice

A study on the role and limitations ofmotorcycles as a means of urban transport inSoutheast Asia
1. Background and goals
Motorcycle ownership and use has advanced rapidly in Southeast Asian regions in recent years, making
motorcycles a major mode of urban transport. Because cities in developed countries have not previously
experienced such a phenomenon, the positioning of motorcycles with regards to traffic planning, designof transportation facilities, and transport operation is unclear, and focus has instead been placed on thenegative aspects of motorcycles, such as increases in traffic accidents. However, motorcycles are compact, highly maneuverable, and have a relatively low environmental impact; thus, they may be a potentially beneficial mode of urban transportation by clarifying their positioning.
Given this situation, this project investigated the actual conditions of motorcycle usage from a variety of viewpoints and elucidated the issue. Specifically, we investigated subjects such as trends in motorcycle dissemination, the effects of motorcycles on traffic flow, traffic operation at intersections according
to the motorcycle ratio, usage of motorcycles as taxis and delivery vehicles, and efforts toward increasing
motorcycle safety. Through on-site investigations, analysis of statistical data, and interviews with expertsin Thailand, Cambodia, and Vietnam, we were able to obtain much new knowledge.
As a representative example, below we present our findings resulting from investigations on actual
traffic operation at intersections according to motorcycle ratios. Based on our findings, we make a proposal for efficient traffic operation at intersections and analyze the effects of conversion from motorcycles to four-wheeled vehicles on transport volumes.

2. Research content
2-1. Investigation of traffic operation at intersections according to motorcycle ratio and a
proposal for efficient operationIntersections are operated in a variety of ways according to the ratio of motorcycles to overall traffic volume. We recorded videos to perform a traffic survey in Bangkok, Chiang Mai, and Phnom Penh, threecities with different motorcycle ratios and different methods for traffic operation at intersections. We
performed a quantitative evaluation of each intersection’s traffic capacity(1) and investigated theProject Leader: Atsushi Fukuda
Professor, Department of Transportation Systems Engineering, College of Science and Technology, Nihon University(1) Intersection traffic capacity: At a single-path portion of a road, capacity is taken to be the number of vehicles that can pass throughthat location in one hour. At intersections, however, traffic passes through from different directions, reducing the number of vehicles thatcan pass. It is therefore important to determine intersection capacities.

A study on the role and limitations of motorcycles as a means of urban transport in Southeast Asia｜157

Motorcycle-onlylaneMotorcycle signal
waiting area

Standard：Motorcycle：Passengervehicle

Figure 1. Three types of intersection configurations

dard intersections with intersections that have a designated area
for motorcycles to wait for traffic
signal changes, the latter have thenegative effect of pushing back thestop line for four-wheeled vehicles,
delaying their start times. However, there was a positive effect inthat allowing motorcycles to collect at the front of signal wait areas
reduced the number of motorcycles running between cars. We thus
found that in situations where
there is a low motorcycle ratio,

Saturated flow rate (four-wheeled vehicles only)intersection configurations that were most efficient for traffic flow control according to the variations inmotorcycle ratio.
We found that an increased number of motorcycles traveling alongside four-wheeled vehicles at astandard intersection can impede traffic of four-wheeled vehicles. In contrast, we found that lanesplitting motorcycles did not have an effect on the operation of four-wheeled vehicles.
Therefore, comparing stan(pcu/lane/h)1850
Standard

Bangkok

Chiang Mai

Phnom Penh

Motorcycle signal waiting area

1800
Motorcycle-only lane

1750
1700
1650

00.2

0.4

0.6

Motorcycle ratio

There is an appropriate method according to the motorcycle ratio
for traffic operation at intersections.
Saturated flow rate on the vertical axis refers to the maximum number of automobiles that can flow into
an intersection without travel interruption during a green light. This is used as the base value for finding
intersection capacity.

Figure 2. Changes in intersection capacity due to motorcycle ratio

158｜Practicestandard intersections may allow for more efficient traffic flow, but the opposite may be the case withhigher ratios. We observed an effect due to establishing motorcycle-priority lanes and to the narrowed
lanes for four-wheeled vehicles. This indicates that the optimal intersection configuration may differ
according to motorcycle ratios.
2-2. Impact on transport volumes due to conversion from motorcycles to four-wheeledvehicles
There is an assumption that increased economic development will promote four-wheeled vehicle usage,
thus lowering motorcycle usage ratios in cities where these ratios are currently high. We therefore analyzed the potential effects of this conversion from the viewpoint of transport volume.
In Bangkok, each motorcycle carries on average 1.2 people, while each automobile carries on average about 1.5. Under the assumption that changes in the motorcycle ratio will not have a large impact on
the average number of riders per motorcycle or four-wheeled vehicle, we calculated changes in cross-Saturated flow rate

sectional throughput (the number of persons passing through an intersection lane per hour) for various
motorcycle ratios. Note that when performing these calculations we assumed optimal intersection configuration for the motorcycle ratio.
We could ascertain that decreased
pcu/lane/h6000
motorcycle ratios resulted in a decreased
number of persons passing through inter5000
Motorcycle
sections, and that such reductions were4000
larger with higher motorcycle ratios. The
3000
current motorcycle ratio in Phnom Penh
Four-wheeled vehicle
2000
is approximately 0.7 and that in Bangkok
1000
is approximately 0.3. This indicates thatPhnom Penh in particular will experience
000.1
0.20.30.4
0.5
0.6
0.7
0.8
serious traffic congestion should fourMotorcycle ratio

wheeled vehicles become more popular.
However, this also means that appropriate
traffic operation for the utilization of motorcycles may increase transport capacity.
Figure 3. Changes in intersection capacity due to motorcycle ratio

3. Conclusions
The various analyses performed in this project indicate that motorcycles are a highly space-efficientmeans of transportation. We believe that the development of motorcycle-based taxis and messenger services in Southeast Asia is a result of motorcycles’ mobility making them well suited as a supplementalmeans of small-scale goods distribution and trunk route transport.
Increased demands for transportation result in increased traffic volume. However, trying to accommodate for this volume by focusing on only four-wheeled vehicles will increase private marginal costs (2)and road usage costs. This translates into decreased total social benefit. In contrast, utilization of space-A study on the role and limitations of motorcycles as a means of urban transport in Southeast Asia｜159

efficient motorcycles can decrease private marginal costs, thereby increasing benefit and allowing more
comfortable road usage.
Motorcycle ownership is currently declining in Japan, but intelligent utilization of motorcycles inSoutheast Asian cities may help prevent the worsening of road conditions that accompanies development of automotive societies. However, attaining this utilization will necessitate the solving of manyproblems. The over-capacity motorcycle-riding that is frequently seen in Southeast Asia is dangerous,
and there is a need for education to improve driving etiquette. As indicated above, there is also a needfor appropriate road maintenance and traffic control better suited to motorcycle operation. Thus, implementing these changes will require not only traffic engineering and traffic planning, but also urban planning efforts.

4. Future outlook
In Japan, there are numerous studies regarding the utilization of ultra-compact vehicles that are larger
than motorcycles but smaller than small automobiles. How best to position the role of such personalvehicles—including motorcycles—as a part of urban transport, and how to connect them with publictransportation, are important issues not only for Southeast Asian cities but also for cities throughout theworld. In the future, it will be necessary to explore the roles and limitations of such vehicles from a variety of viewpoints regarding environmental and spatial efficiency and traffic safety issues, leading toward
the development of an ideal traffic system.

(2) Private marginal cost: An increased number of automobiles results in congestion and lower traveling speeds. Private marginal cost isa generalized cost referring to the amount of worsened congestion resulting from the increase of a single car (Social marginal cost: Under
these conditions of increased number of automobiles, worsened congestion results in increased costs due to congestion not only to theadded car, but to other cars as well. Social marginal cost refers to this amount of increase).