URBAN TRAFFIC CONGESTION: THE PROBLEM
Paper Published in the Economic Review, Sri Lanka
Amal S. Kumarage
Transportation Engineering Division,
University of Moratuwa, Sri Lanka.
URBAN TRAFFIC CONGESTION: THE PROBLEM AND
To many people, traffic congestion is an irritant because it throws their personal schedules in to
chaos. To others conscious of the value of time in their economic pursuit, it is a financial loss.
Yet to some others, it is an easy excuse for being habitually late for appointments and for some
others it is a convenient conversation starter. But most often, all these people tend to shrug their
shoulders and appear to accept that this part and parcel of the travails of urban living.
This article examines the proposition if traffic congestion is something we just have to learn to
live with or if there are indeed initiatives that could be taken to reduce and manage it within
tolerable levels. But ahead of answering that, we need to ask some basic questions:
• Why is there congestion?
• What are the effects of congestion?
Put simply, traffic congestion means there are more vehicles trying to use a given road facility
than it can handle- without exceeding acceptable levels of delay or inconvenience. In Colombo
and other major cities, this occurs mostly during certain times of the day- we call peak periods or
rush hours. There are two clear parameters within a single equation that causes congestion, which
is the balance between the demand and the supply of road space.
The demand for road space arises from the universally observed desire of individuals to own and
use a motor vehicle. As incomes increase and technological advancements reduce the real cost of
producing a motor vehicle, more and more persons find the financial means for owning and using
a motor vehicle. However, motor vehicles do not come without their share of physical and
environmental limitations. A motor vehicle in the first instance requires road space to operate
freely, parking spaces at residences and work places. Increase of motor vehicles (the demand)
often outstrips the provision of road space (the supply) in many countries. The result is traffic
According to the TransPlan Model (UoM, 1999) average traffic speeds within the Colombo
Metropolitan Region (CMR) have dropped to around 20 kms/hr today. The typical corridor
(major artery) speed is around 10-15 kms/hr within Colombo City. Traffic congestion may be
considered a problem, by many, they often fail to see the extent of its impact on the community
and country. These impacts could be further discussed as:
Economic Growth: A good transportation system is an important selling point to communities
that desire to attract development that provides for employment and growth of a city. If transport
costs due to congestion increase, goods and services produced within that city tend to increase in
costs thus losing competitiveness in international markets. Efficient transportation access is
therefore a very important consideration as it has a direct impact on sound and sustainable
economic growth and productivity. The cost of congestion in the Western Province of Sri Lanka
is over Rs 20,000 million per year (around 2 percent of Regional GDP). This includes the cost of
productive time and wastage of fuel.
Quality-of-Life: To some people, congested highways are a symptom of deteriorating quality-of-
life-in a community. The amount of time that is spent on commuting to and from work is also in
reality, time that is taken away from social interactions or pursuit of activities that have a personal
value and satisfaction.
Environmental Quality: Congested road conditions can have a detrimental effect on the
environment, in particular air quality and noise pollution. Congestion arises due to increase
vehicles on the road. Ironically this is the time when there are the most number of people on the
roads as well. This means that many more people become vulnerable to respiratory diseases such
as asthma -widely prevalent today.
Anti- Social Behavior: Increasing social problems referred to as Highway Rage (or Road Rage)
experienced in many countries where drivers show hostility to each other most often due to the
frustration of slow moving traffic is also becoming a serious social problem.
STRATEGIES FOR MANAGING TRAFFIC CONGESTION
Road users and political leaders need to be appraised what options there are for Colombo or any
other city to manage traffic congestion. These management strategies could be discussed under
short term and long term options. Most successful approach for Sri Lanka would be to adopt a
dual strategy so that immediate respite and permanent solutions are initiated together.
The Short-Term Strategy
This strategy has two distinct approaches. The relative merits of each and the suitability of them,
for Colombo and other cities in Sri Lanka are discussed below:
Managing the Transport Supply: Managing the transportation system by adding new facilities
or by making operational changes to improve system performance is the most common response
by engineers and even politicians and administrators to solve congestion problems. These
measures can be better understood by classifying such attempts as follows.
1. Adding new transport infrastructure capacity: This means new roads, expressways and
railways that can carry more vehicles. Even though this is almost always the ‘first-option’
suggested by road engineers and police alike, this is usually very expensive and often socially
prohibitive in urban areas. However the bigger limitation in this approach is that road
construction in urban areas is often considered to generate more traffic in the long term, and
the idiom that ‘traffic fills whatever road space provided’ is a well-established fact. For
example, the author has shown elsewhere (Kumarage, 1999) how the proposed Katunayake
Expressway could very well increase congestion within the city, even though there might be
some respite for a period of time on t he existing A3 highway.
2. Improving existing infrastructure for increasing capacity: A less expensive approach is to
identify bottlenecks and increase capacity at these places. Signalizing an uncontrolled
intersection (e.g. Katubedda Junction) or street widening of bottlenecks (e.g. Kadawatha
town) or providing for a grade-separated intersection (e.g. Ragama fly over) would fall within
this category. However many such attempt are also unlikely to solve traffic problemsin the
long term, as these bottlenecks often control the flow of traffic beyond them and when they
are eased, the problem shifts further down stream- a problem identified as ‘migration of
3. Re designing existing infrastructure for increasing capacity: Converting existing road space
for high occupancy vehicles either by introducing bus lanes or providing bus ways
(experimentally tried in Sri Lanka last October, but widely used in many European cities- de
Silva et al, 2002). In some cities, entire roads have also been converted to pedestrian only
streets. Removal of on-street parking is another successful method used (tried successfully in
1997 but later lapsed due to Police disinterest- Kumarage, 1999) especially in the peak period
in the peak direction. This is a successful approach increasingly used in cities throughout the
world, that have correctly identified that carrying more people in to a city is more important
than merely allowing for more vehicles to come.
4. Operational Improvements to existing infrastructure to increase capacity: These include
operational changes to increase the capacity of a transport system. These measures include
introducing reversible lanes during peak periods, (for example, the Galle Road between
Maliban and Kalubowila Road, has five lanes. The middle lane can be made into a reversible
lane, with the outer lane in the peak period turned in to a bus lane); introducing a right-turn
phase in a traffic signal, ensuring better police enforcement, one-way systems that reduce
traffic conflicts and
expanding the public
transport network are
approaches. The use
Technology has also
detection programs, motorist information systems, and towing/enforcement efforts that can be
used to minimize the effects of accidents and other non-recurring incidents and increase the
capacity and reliability of the network.
Managing the Transportation Demand: In its broadest sense, demand management is any
action or set of actions intended to influence the intensity, timing, and spatial distribution of
transportation demand for the purpose of reducing the impact of traffic flow. These can be
categorized under the headings.
a) Re-distribution of the spatial form of the demand for transport: These include the urban re-
planning and the relocation of certain land uses that may cause traffic congestion. For
example, there has been a plan for many years to relocate the wholesale trade activities in
Pettah to Orugodawatte (University of Moratuwa, 2000). This (long overdue project) would
reduce the freight traffic to the Central Business District area and ease traffic congestion
considerably. Similarly there is a proposal (Kumarage, 2002) to decentralize the Pettah Bus
Terminal so that fewer buses would come to Pettah and Fort areas. Relocation of
administrative functions that attract travel is a common strategy (e.g. relocation of passport
b) Re-distribution of the temporal pattern of the demand for transport: This is also known as
demand spreading. There are many methods adopted in different countries to spread the traffic
during peak hours. Since it is when large numbers of people travel at the same time to the
same locality that cause traffic congestion, there is now an effort in other countries to Stagger
Work Hours (see Table 1). This requires offices opening and closing over a longer time span
(e.g. spread from say 8 am to 9.30 am). This also applies to separating school times from
office time and even spreading school opening times between different areas or types of
schools (e.g. private and state schools could start at different times). Flexible Work Hours is
another methods whereby workers are allowed to report for work over a period of time rather
than at an exact time. Electronic Road Pricing is another method used in some cities,
whereby peak period road use could be tolled higher than off peak so that some demand is
spread to other hours. Prohibiting delivery vehicles during working hours in a city, is another
method of designating goods transport to night times when road capacity exists.
Table 1: Proposed Work Hours
Sector Proposed Start
State Schools 8:00 8:00 14:00 14:00
Private Schools 8:15 7:30/8:00 14:15 13:30/14:00
Other Educational Institutions 8:30 8:00/8:30 Varies Varies
Public Sector Offices 8:45 8:45/9:00 16:30 16:45/17:00
Private Sector Offices 9:00 9:00 17:30 17:30
Banking/Financial Sector 9:30 9:00 18:00 17:30
Retail Business 10:00 10:00 18:30 18:30
c) Re-distributions of demand between the modes of transport: This is done in order to move
persons from modes of transport more likely to cause congestion to more space efficient
modes of transport. This can be done by say increasing the quantity and quality of public
transport. Financial penalties may also be used for this purpose. Imposing Road Tolls (where
cars are taxed and buses allowed free as in Singapore) and increasing Parking Charges to
commercial values (most European & U.S. cities) is another method. In some cities reducing
parking availability and imposing time limits for parking is an established strategy (e.g.
London). Generally re-distribution is favorable when passengers are induced to move from
high space utilizing vehicles (e.g. cars and motor cycles) to lower space utilizing vehicles
(such as buses and other modes of public transport). Park and Ride facilities are also
encouraged, which enable people who would be travelling by private cars to park their
vehicles away from a city and take a bus or train from there (a proposal for this has been made
in Kumarage, 1997).
Solving traffic congestion in the long-term however requires even wider strategies and policies.
These can be identified in to four categories. These are also discussed in brief.
a) A land-use strategy compatible with transport capacity
b) A Vehicle Ownership strategy compatible with road capacity
c) A strategy for public transport compatible with population density
d) A strategy for new modes of public transport compatible with personal incomes.
a) A land-use strategy compatible with transport capacity: The Colombo Metropolitan Regional
Structure Plan (UDA, 1999)
provides a good case study on
how a sustainable and
balanced land-use strategy can
be developed based on the
transport capacity that can be
provided. The combined land
use- transport strategy adopted
in the CMRSP aims to provide
for more space efficient modes
of transport within the CMR
together. The main radial
arteries to the City are
proposed to be developed as
High Mobility Roadsfor fast
commuter travel (by banning
introducing signalisation etc).
Furthermore, it proposes to
develop the Colombo City as
mixed high-density land use
and to facilitate the planned
formation of six satellite city centres. The proposed outer ring road in this case is intended to
connect these satellite cities while simultaneously providing for an orbital route around
Colombo and its suburbs for inter-regional traffic.
b) A Vehicle Ownership strategy compatible with road capacity: Vehicle ownership is associated
with increase in incomes. It is also represents an important feature of choice of travel.
Increases in vehicle ownership however, requires more road space, parking space and
measures to control air pollution etc. Therefore, to properly plan the land use in the CMR or in
any city, the levels of vehicle ownership that can be sustained therein has to be understood.
The present rates of vehicle ownership in Sri Lanka, is around 74 vehicles per 1000 persons.
This increases to 97 per 1000 in the CMR. In Colombo District, this increases further to 141
per 1000. In Colombo City, this is even higher at 262 per 1000. The fact that within most parts
of Colombo City and also in many parts of the Colombo District, traffic congestion is a
regular feature indicates quite clearly that the present level of vehicle ownership therein,
cannot be sustained. This as described before, is because the demand that these vehicles
generate cannot be matched by the provision of increased road space. This means that the
saturation levels for the present transport infrastructure appears to have been reached in these
areas. This is saturation level is based on three distinct parameters.
• Population Density
• Performance of Public Transport
• Road Length
According to the Colombo Traffic Study, (UoM, 1995) the share of public transport
within Colombo City is around 50%. Within the CMR it is estimated to be around 60%.
The national average also appears to be around 60- 65%. The population density in
Colombo is 174 persons/ha and according to CMRSP projections, set to increase to nearly
200 by the year 2010. According to the same projections, the population density, which is
30 persons/ha in Colombo District at present, is set to increase to 40 persons/ha. The road
density in metres per person, which is an alarming 0.2 in the CMC, increases only up to
1.4 in Colombo District. Table 2 shows the corresponding land use density, incomes and
performance of public transport associated with the respective levels of sustainability in
On an international comparison, the ownership of vehicles in cities in the USA, Canada
and Australia show that sustainability levels can be as high as between 600 to 700 vehicles
per 1000 persons. These rates are associated with, high incomes and low levels of public
transport use at less than 5%. The population density of these cities is generally low and
below 25 persons per hectare. Most European Cities on the other hand, maintain incomes
comparable to the earlier group of cities, but have significantly higher public transport
patronage of around 25%. In these instances, the vehicle ownership rate appears to
saturate at around 300 to 400 vehicles per 1000 persons. In these cities however,
population density is higher (25-75 persons/ha). Most cities also apply some degree of
traffic restraint usually in the form of parking limitations. The third group refers mostly to
Asian cities, where vehicle ownership levels seem to taper off at even lower levels. Public
transport in these cities is between 50-80%. This is achieved by intensifying
improvements to public transport and simultaneously applying equally intense traffic and
even vehicle ownership restrain measures. These cities have much higher population
densities at over 75 persons/ha.
Table 2: Vehicle Ownership Saturation Levels with Urban Parameters
Low < 25 > 4 < 5% 600-700 Little or no restriction on
Moderate 25-75 1-4 15-35% 300-400 Some traffic and parking
High > 75 < 1 50-80% 200-300 Traffic and Ownership
Based on a comparison of the above cities in Sri Lanka, which in most cases have low
road densities and high population densities and are presently public transport oriented,
would only be able to sustain relatively lower levels of traffic and correspondingly lower
vehicle ownership. In the case of the Colombo City saturation has already been reached,
whereas in other parts of Colombo District, where on account of the fact that public
transport has a good coverage, it would be most desirable to target for saturation levels of
around 300 vehicles per 1000 persons. In this case, there is some growth possible before
Such a situation can only be arrived through specific interventionist policies that bring
about balanced transport growth (e.g. as the New Deal Transport Policy in the U.K.). It is
clear that without any interventionist measures, vehicle ownership will continue to
increase with incomes and traffic congestion will continue. This should then influence all
transport policy and infrastructure planning within the CMR and its sub regions. This
would mean that policy directive should be aimed at controlling vehicle use starting from
the CMC and then spreading to Colombo District before extending to all of the CMR.
Such policy should take into account steps to maintain the public transport share, while
planning for traffic restraint measures and measures to manage the ownership and use of
c) A strategy for public transport compatible with population density: It is was shown earlier that
public transport becomes a necessary and appropriate mode of travel when population density
is high and density of roads is low at the same time. In such a scenario when incomes increase,
it is public transport that can provide sustainable transport. Therefore it is evident that the
backbone of an efficient and sustainable transport system in the CMR would essentially center
around a good public transport system. Particularly for travel within the CMC and on the
Such a strategy would require the following policy initiatives, projects and programs to give
priority for public transport use and to restrain private vehicle use- a two pronged approach
that has been successfully used in many cities throughout the world (e.g. Singapore, Tokyo,
most European Cities).
• Implement a Parking Policy where parking spaces are restricted & where parking fees are
increased in keeping with the demand for the limited spaces.
• Implement an electronic tolling system for the roads within the CMC at peak periods so
that inefficient use of road space by low occupancy vehicles during peak periods could be
discouraged by a toll.
• Encourage the operation of road and rail based park and ride systems.
• Divert port-based freight traffic from road to rail.
• Set up regional distribution centres for agricultural produce to minimise travel related to
d) A strategy for new modes of public transport compatible with personal incomes: The CMRSP
(UDA, 1999) has proposed a People Mover System for Colombo City as a means of
improving public transport as well as introducing a higher level of service in public transport.
This is essential if pubic transport is to be a viable alternative for people whose incomes are
increasing. They would look for quality in public transport. If passengers, whose incomes are
increasing all the time, do not find adequate quality, then the need to own and then use a
private vehicle would be un-manageable. Therefore, the need for a new public transit system
has a wider connotation than its immediate financial viability. It should be a part of a strategic
plan of managing mobility in the CMR. The Colombo Urban Transport Study (WS Atkins &
University of Moratuwa, 1999) have recommended a Light Rapid Transit (LRT) – also known
as the modern day trams for Colombo City and for two radial corridors. These systems are
being introduced as alternatives for road
building programs (e.g. Bangkok or Kuala
Lumpur) and are investments that will most
likely be most effective in managing the
future demand for transport and the
management of traffic congestion in our
• De Silva, G.L.D, et al, The Design of a Bus
Lane for Sri Lanka, Final Year Project Report,
University of Moratuwa, 2002.
• Kumarage, Amal S., Transport Plan for
Colombo City, Urban Development Authority, Colombo, 2001.
• Kumarage Amal S. A Review of the Colombo Katunayake Expressway Project, Report submitted to
H.E President, 1999.
• Kumarage Amal S., Traffic Management for a Major Urban Artery - Galle Road, Colombo, 6th
International Seminar on Transport, Chartered Institute of Transport, Colombo, March 1998.
• Kumarage, Amal S., A Park & Ride System for Colombo, Urban Development Authority, July 1997.
• University of Moratuwa, Transport Proposal for Orugodawatte Wholesale Complex for Urban
Development Authority, 2000.
• University of Moratuwa, TransPlan V3: A Computer Algorithm for Traffic Assignment & Forecasting
in Sri Lanka, University of Moratuwa, 1999
• University of Moratuwa, Colombo Traffic Study for Urban Development Authority/Colombo
Municipal Council, 1994.
• Urban Development Authority, Colombo Metropolitan Regional Structure Plan –CMRSP, 1999
• WS Atkins & University of Moratuwa, Colombo Urban Transport Study Stage 2, Ministry of
Transport & Highways, 1999.