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Tuesday , 26 March 2024

Urban Transport Energy Consumption:Determinants and Strategies for its Reduction

Dangerous trends in terms of greenhouse effects and the possible future

Urban density is mostly regressing in the cities in Western Europe (-20% in twenty years). Despite gains in the use of public transport (except in Australia), automobile use has grown significantly, mainly as a result of lengthened commuting distances from home to work.

These worrying trends are likely to continue. There is a global trend in the development of urban structures: On the one hand, cities grow larger as do Central Business Districts. As they grow, the centres lose their compactness and therefore, the proximity factor which was their main attraction. Inevitably, secondary centres will emerge so that the degree of monocentricity lessens as the size of the city increases. On the other hand, incomes and mobility increase in most megacities, densities diminish and, as a consequence, even the role of public transport declines. Obviously, these are not desirable trends in terms of environmental sustainability.

Answer lies in Atlanta and Barcelona

A comparison between two cities, Atlanta and Barcelona, whose demography and GDP per capital are similar, summarises the range of possible futures for the cities of the South. In Atlanta, the greatest distance between two points of the urban area is 137km, as against 37km in Barcelona. The small travel distances in Barcelona, due to the high density, enable its citizens to walk for 20% of their trips. In Atlanta, pedestrian travel is not even recorded. As a result, CO2 emissions connected to urban transport are 11 times lower in Barcelona than in Atlanta. But the average density is not the only factor to influence travel distances. In a dominantly monocentric city, trips are generally shorter since they are mainly from the periphery to the CBD.

Dense, mixed, monocentric, highly structured through city planning and a transport system weighted in favour of public transport, supplemented by bicycles and walking, in a word, Barcelona (or Hong Kong) rather than Atlanta should be the overall model for cities of the South. Many of them already have these characteristics; so the issue is not so much how to increase density or reduce the use of cars, but rather how to preserve these beneficial urban structures. And yet, this does not seem to be the way we are going.

What should be done?

The need for urban planning integrating the “transport supply – land use” relationships

The demand for travel is a derived demand. When the urban structure changes, so does the demand for travel. Modifications in the transport supply lead to a multiplicity of changes: Making choices regarding routes, sequence and mode of travel are all involved, but also destinations and the number of trips and even more fundamental decisions such as the purchase of a vehicle or the location of jobs, activities and housing. In the medium and long term, modifications of transport conditions entail a revision of certain choices of activity, such as where purchases are made and where to work and live. The urban structure itself is therefore also modified.

The most significant benefit in the long term of a Mass Rapid Transit (MRT) system, bus or rail based, is probably that it concentrates urban development in accessibility corridors. It provides the necessary conditions to resist diffuse urban sprawl. But this possibility remains virtual unless MRT development is linked with appropriate land use and transport policies. Construction of an MRT increases mobility leading generally to an increase in urban area. It is therefore necessary to complement the construction of an MRT with a land use policy.

This pleads in favour of planning which explicitly integrates the effects of locating and relocating due to the sitting of transport infrastructures i.e. integrating the interaction between transport and land use. Since these interactions are extremely complex, simulation models of urban dynamics can be used to evaluate the impact of integrated transport and land use policies based on an in-depth understanding of the selection mechanisms for locations and transport.

Transport Policies

Progressing from the most superficial to the most deep-rooted urban transport-related emission determinants, i.e. from “end of pipe” technologies to action on the need for transport (via the structuring effects of transport infrastructure on the urban form itself), including action on modal choice, transport policies cover an array of practical measures ranging from improving vehicles to offering low-pollution, fast and comfortable public transport (so that even car owners may choose to use them), as well as inexpensive (so that the city can be accessible to the poor), including economic instruments with an impact on prices, generally aiming to support and complement other measures based on regulation and infrastructure improvements.

Improving vehicles and economic instruments: The main measures that can be taken to improve the environmental efficiency of vehicles are the following: Improving the quality of road infrastructure which has a direct effect on the energy consumption per kilometre of the various types of road vehicles; Improving vehicle efficiency – reducing weight of cars, enhancing aerodynamics, improving engine performance for motorcycles, promoting four-stroke engines; Improving fuel quality and introducing low-pollution fuels (natural gas, LPG, ethanol, methanol, etc.); and implementing environmental regulations – set programmes for vehicle inspection and maintenance and for the scrapping of obsolete vehicles.

These regulatory and technical measures may be supported and complemented by economic instruments based on the general principle of internalising, generally through taxation, the cost to the environment of the various modes of transport, to act as a deterrent against using the high-pollution varieties.

Donors, the World Bank in particular, highly recommend such measures. They are of course advisable but they can lead to a significant increase in the cost of urban transport, for the poor in particular who are intensive users of highly polluting and dilapidated shared taxis, buses and rickshaws. Unless there is some alternative means of transport, cleaner but just as cheap, this kind of policy may be good for the environment but not so good for the poorer citizens, hence a dilemma. It does however turn out well in some cases, as exemplified by the relative success obtained in Delhi when buses and rickshaws transferred to gas.

However, the lack of control over modal distribution and more essentially over the need to travel is the reason why this kind of measure does not quite meet the challenge of urban dynamics in the cities of the South.

Promotion of Mass Rapid Transit (MRT): The urban structure of many cities in the South is still well suited to transport systems based on transit corridors. Even severely congested cities are more often car-saturated than morphologically dependent on cars, as yet. Contrary to car-dependent cities with highly scattered activities, in this context major passenger flows can be organised and it is therefore possible to develop Mass Rapid Transit systems.

MRTs generally operate at regular frequencies, along exclusive “right-of-way” lanes. MRTs have a greater capacity than traditional public transport (buses, vans, “busetas”, shared taxis, etc.). MRTs are always provided with infrastructure to allow integration with other transport modes.

MRTs are generally classified into four different types: Heavy Rail metro; Commuter Rail (CR); light rail metro (Light Rail Transit – LRT); and the Bus Rapid Transit (BRT). Heavy rail systems are the costliest MRTs, but their theoretical capacity is the highest. Experience has shown that it is possible to cover the cost of operating heavy rail systems in high density urban areas, but they generally need large public subsidies. Because of its high cost, heavy rail does not meet the needs of rapidly expanding cities of the South.

Light Rail Transit (LRT) is an electric metropolitan rail system operating with short trains using dedicated corridors, elevated, underground or street-level. LRTs generally include tramways, although these often run among other traffic without the benefit of exclusive corridors. Light Rail Transit seems more suitable for prosperous cities. Their capacity is equivalent to that of BRTs, but they seem to be on the wane in cities of the South.

Commuter Rail or suburban rail is a system transporting passengers within an urban area or between a city and its suburbs. It differs from the two metro types because its carriages are heavier, it has longer routes and the tracks are generally part of an older rail system.

Many cities have developed variations on the theme of “improved bus service” and the Bus Rapid Transit (BRT) concept is more about a set of recommended practices than one single technique. BRTs operate using high technology buses along exclusive corridors, generally at street level. Their passenger boarding and discharging systems are fast. They use efficient ticketing methods at the entrance of comfortable stations, on-board technology for monitoring and managing operations, on-line passenger information systems and infrastructure for modal integration. BRTs are much more than a bus service operating along dedicated corridors: They are an integrated system, optimised to achieve transport quality and capacity very similar to that of rail systems.

In the case of poor cities, a significant impact on the modal distribution of travel is only in fact possible with bus-based MRTs, i.e. BRTs. Because of their high cost, the new metro systems can only be installed over a limited area and they have neither the same capacity as BRTs to satisfy all the demand, nor enough flexibility to be able to adapt to an expanding and fluctuating urban structure.

The first reason for the current popularity of BRT technology is that it is low-cost. Its infrastructure is relatively lightweight so that the total cost of investment is reduced by as much as a factor of 100 compared to a heavy rail metro system. For an equivalent investment, the BRT can serve up to 100 times the urban area covered by a metro, said experts Wright and Fjellstrom in a research. Also, since their infrastructure is simpler, less time is needed for their construction. Elevated or underground metro systems, may take more than three years to build. Also, with a BRT, the flow of passengers served can be close to the numbers in a metro system. They provide quality service which means that they are attractive to car owners for whom this point is critical at an affordable price for the needy, without compromising the profitability of the whole operation.

Metro systems have in particular the advantage of reduced labour costs because only one driver is needed for a large number of railcars. But in poor countries, low salaries mean that other components far outweigh labour costs. A USGAO study (2001) for the UN, compares six American cities with both a BRT and an LRT and it confirms that the operating costs of an LRT are about 1.6 to 7.8 times higher than those of a BRT.

Environmentally, all MRTs are an improvement in so far as they are a replacement for high pollution automobile and bus travel. Although in theory, the most energy-saving MRT is rail transport, load-factor is also a decisive factor. Emission also obviously depends on the energy source used to produce electricity. In Bogota, the diesel fuel used for the BRT emits CO2, whereas the Quito BRT uses hydroelectric power and does not.

Non-motorised travel: In most cities of the South, walking and cycling are still largely prominent in the modal distribution of travel. And yet, they are more often than not ignored in the city planning process. If “urban design” is not appropriate, if there is no separation from street traffic, or even no footpaths on which to walk, these non-motorised modes of travel are dangerous and tend to disappear, despite the fact that they represent a modest investment.

Solutions

There are four possible urban structures the cities of the South can choose from: A sprawling polycentric city (Atlanta), a dense monocentric city (Barcelona), a city made up of a relatively dense centre surrounded by satellites and a dual city made up of a modern international standard type centre more or less loosely connected to a traditional city. Since environmental constraints impose a limitation on expanding the use of cars, even if they were to become more environment-friendly, the first alternative, i.e. the sprawling city, is to be avoided.

For the three other types of structure, constructing an energy-sustainable urban future is not, theoretically, an impossible task. To achieve this, urban energy consumption needs to be squeezed between transport and land use policies: Make motorised vehicles less polluting, discourage the use of private vehicles, promote efficient public transport systems, specially BRTs, adjust urban planning laws as well as land use and built-surface regulations to help concentrate private investment in highly accessible areas generated by the construction of an MRT, to reduce mobility requirements thanks to greater density and function mix, and to encourage non-motorised travel by appropriate urban design and meshing together of the various modes of transport.

Since the protection of a global public good the climate is in question, then urban policies should qualify for incentive measures and CDM type transfers. But practically, it is very difficult to prove that transport and land use policies, whose objectives are obviously multiple, satisfy the additionality constraint. Technically, it means that when an urban policy succeeds in reducing pollutant emission, it is very difficult to separate emission reduction which is simply a favourable consequence of an urban policy in pursuit of other objectives from additional reductions connected to a specific effort to combat greenhouse effects conferring the right to participate in an emission allowance trading scheme, in whatever form.

And clearly, as is the case on all the greenhouse gas emission reduction fronts, it is up to the cities of the North to lead the way and it is the countries of the North that must encourage massive transfer of the best technologies.

Benoit Lefevre
Research Fellow
IDDRI, Sciences politiques

 

 

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