Traffic management strategies to reduce air pollution J. Perez-Cerezo Environment, Transport & Planning, General Pardinas, 772 6;

Transcription

1 Traffic management strategies to reduce air pollution J. Perez-Cerezo Environment, Transport & Planning, General Pardinas, 772 6; Abstract Several European Governments and cities have developed strategies oriented to reduce vehicle pollution, with more or less success. Many initiatives have been undertaken or are on-going in this frame. A deep revision has been undertaken, that includes most of the European initiatives that are being developed. 1 Introduction Air pollution is one of the main priorities for Local and National Authorities. However, it is frequent that measures towards traffic (that main pollution source in most of the cities), do not only deal with environmental aspects, but also with the general characteristics of urban traffic to obtain, at last, a raising in people's life standard. This is why there are only a few number of measures that have exclusively environmental implications. Long term planning is a very important aspect to front the problem of air pollution, as cities which do not have a great problem could face situations such as those of Athens if a careful evaluation of the evolution of air pollution is not made. The strategies that are explained hereafter, are structures as follows: Traffic measures. Public transportation. Freight transportation. Alternative modes of transport. Tools to identify the most contaminant vehicles.

2 142 Urban Transport and the Environment 2 Traffic measures 2.1 Priority for buses and taxis These kind of measures could decrease the use of private vehicles, and thus reduce the number of traffic jams and the air pollution. Bus lanes are the most common means used to give priority to buses, which in some cities can also be used by taxis. Besides, modern control systems can be programmed to give priority to buses - which would be equipped with an electronic sensor - in intersections. The following table shows the environmental benefits of implementing these kind of measures, as well as the reduction in the time that trips take to passengers: Kind of Measure Time Decreased (%) Bus Emissions Decreased (%) Lanes in peak hours Only-bus streets Turn priority Although the decreasing of the bus emissions is very significant, its relative importance regarding all the vehicles moving in the city is quite small. This is why it could be concluded that measures that give priority to buses are more effective in order to improve the situation of traffic than to reduce air pollution. 2.2 Street lights control systems Several modern cities use Urban Traffic Control Systems (UTCS) that manage traffic lights in the city. Amongst the most common systems we have TRANSYT, SCOOT and MOVA. The implementation of those systems immediately increases the mean speed of traffic and reduces the number of acceleration-braking cycles, that reduces fuel consumption, and therefore, emissions to the atmosphere. It has been proved that TRANS YT can save up to a 3% of the fuel used by urban vehicles, SCOOT can save up to a 5% more fuel than TRANS YT in peak hours, as an experience in Worcester proved (Nelson et al., 1995). Besides, the implementation of these systems could improve the capacity of streets and the conditions of traffic. This may cause an increase in the use of private transport so, in the worst of the cases, air quality could enworsen.

3 2.3 Traffic calming measures Urban Transport and the Environment 143 There are several measures designed to slow down traffic and therefore increase safety in the roads. These measures have important consequences regarding the environment. Traffic calming measures include road closures, vehicle weight and size restrictions, one way streets, mini-roundabouts, priority changes, chicanes, carriageway marking, humps, etc.. Amongst these, we may distinguish between vertical and horizontal traffic calming measures. Vertical calming measures, and particularly road humps - the most spreaded kind of vertical calming measure -, are one of the most effective measures regarding traffic slow down and safety. However, some demonstrations developed in Austria (Kuntschen, 1994), proved that emissions raised in those streets provided with road humps (NO% emissions were increased up to 10 times, and CO emissions up to 3 times). This should be due to a change in the driving behaviour, as the number of accelerating-braking cycles are much raised. Horizontal calming measures - mini-roundabouts, chicanes, curves, etc. - are more effective when implemented together or mixed. These mixed measures have been successfully implemented in some areas in the County of Cambridgeshire. 3 Public Transportation Public transportation policies are usually including environmental aspects amongst their goals in several European cities. Public transport is mainly recommended in go and return journeys to working places in dense centers, for local shopping and for longer journeys between active urban centers. The main characteristics that should be taken into account when developing public transportation policies are: Quality of the service. Fares. Fare structure. At present, some technical improvements regarding fuels have favoured the decreasing of emissions from buses. These improvements, that are being implemented in the frame of the ENTRANCE project, are oriented towards to main directions: Buses using natural gas as a fuel. These buses are actually in service in some Spanish cities, such as Madrid and Valladolid. Buses that have an electric/diesel hybrid engine.

4 144 Urban Transport and the Environment 4 Freight Transport Freight transport has certain specific characteristics, so a particular study of this sector may be of interest. This kind of transport is widely spreaded in many European urban areas. For example, in Zurich it represented a 12% of the whole of the urban traffic in In the future, it seems that freight transport will be more developed than private transport, so its relative importance will raise. The European Union Directive 83/35I/EEC indicated that vans weighting less than 3.5 tons caused a 25% more pollution than private vehicles in similar conditions. This estimation proved the high level of emissions caused by freight transport. Several years after this Directive was published, the CORINEAIR emission factors proved that CO emissions coming from vans weighting less than 3.5 tons was around double than those coming from private vehicles. COST Action 321 (Urban Goods Transport), in which Environment, Transport & Planning participated, developed a report that comprehensively documents the initiatives that could be used to improve freight transport from the strategical and an environmental points of view. Some of these are the following: 4.1 Reduction of packing volume For many products the volume of packing materials is considerable. Some transports fully utilize vehicle capacity in terms of volume but not in terms of load (the so-called volume transports). Reduction of packaging volume may be achieved though improved transport quality, optimization of packaging, and through changes in customers attitudes. This may result in higher net loading rates and less truck trips and, therefore, a reduction in the use of energy and emissions. 4.2 Transport coordination A substantial part of goods transport in urban areas is individual transport, which is one of the reasons for the low capacity utilization. Optimal success should be obtained from this measure through the announcement by the retailers of their transport demand to a coordination center, in which several companies may participate. The main benefits that could be obtained from this measure are a congestion reduction, a local pollution reduction, safety enhancement, and a support to local and transport economy. 4.3 Regulation of load/unload periods The adequate regulation of these periods may have a certain importance. It is important not to deliver on peak hours, and delivery times could be different depending on the area of the city.

5 Urban Transport and the Environment 145 If special unloading areas were provided in certain urban areas, freight transport vehicles should not collapse traffic in those places where the road capacity is low. Besides, if this unloading areas were provided, surface parking areas would be reduced, so public transport would be enhanced. 5 Alternative modes of transport 5.1 Bicycle Amongst the most common alternative modes of transport, the bicycle is, perhaps, the most spreaded. The bicycle is widely used in some central Europe countries, such as Denmark or The Netherlands. It is easier to be used inflatand dense cities, where trips could be not too long. From an environmental point of view, bicycle is the ideal mode of transport, both regarding acoustic pollution and air quality. This is why the use of the bicycle will raise if: Safety is improved. Bicycle lanes decrease the number of accidents suffered by cyclists. However, it is not always possible to construct them, as central areas of many cities are too narrow. It was possible to park the bicycles in educational centers (schools, high schools, universities, etc.), public centers, working areas, etc.. Climate has also a great influence over the use of the bicycle as a mode of transport However, in Southern Europe, cycling is considered more a sport than a mode of transport. In Europe, there is a very high number of homes where at least a bicycle exist, and most of the journeys are normally of less than 8 km., so, in theory, the conditions are good in order to expect a spreading of this mode of transport. 5.2 Pedestrians Pedestrination of certain streets in the city centers is a normal strategy in European cities. There are several variations of this strategy, such as allowing buses and taxis to travel through these streets. Many cities are trying to increase their pedestrian areas, that normally count with the approval of most part of the citizenship. However, pedestrination is a measure that should be accompanied by others: if traffic is forbidden is certain streets, a chaos could be provoked in the rest of the city. In general terms, pedestrination should be accompanied by improvements in the public transport network. Otherwise, the global quality of air will not be improved.

6 146 Urban Transport and the Environment 6 Tools to identify the most contaminant vehicles Around the 60% of the emissions come from approximately the 10% of the vehicles (Fujita et al., 1993). This means that a scarce number of vehicles pollute up to 10 or even 20 times more than the average. In some countries, vehicles must go through periodic revisions in which their emissions are analyzed. Those vehicles that pollute more than a level established by law must be repaired. Remote sensing device (EPA, 1993) are instruments that can identify emission levels while cars are moving. An infrared radiation is projected across the road, and the device measures the CO and VOC's concentrations. Each car is identified with a video camera or a snap-shot camera. If emissions are higher than those permitted, administrative measures and/or reparation should be accomplished. This system is widely used in the United States, and it is starting to be used in certain areas of Europe with successful results.

7 Urban Transport and the Environment 147 References 1 Bayliss, D. Road Passenger Transport in European Transport, Institution of Civil Engineers, London, Bayliss, D. Urban Traffic Management. Policy and the Environment, OCDE Publication Service, Paris, COST 321 Management Committee. Measures to Improve Urban Freight Transport, Commission of the European Union, Brussels, Department of the Environment. The UK Environment, Government Statistical Service, HMSO, London, Department of the Environment & Department of Transport. Reducing Transport Emissions through Planning, HMSO, London, Dietrich, W Urban Goods Transport Planning, Technical Subcommittee of COST Action 321 "Urban Goods Transport", COST Secretariat, Brussels, Environmental Protection Agency (EPA). Remote Sensing, a Supplementary Tool for Vehicle Emission Control, Office of Mobile Sources, Fact Sheet OMS 15, Washington D.C., August Fujita, E., Croes, B, Bennet, C & Lawson, D Comparison of Emission Inventory and Ambient Concentration Ratios of CO, NMOG, and NO, in California's South Coast Air Basin, California Air Resources Board, California, Garcia Guemes, C Local Strategies to Reduce Air Pollution: an Approach to the British Situation, TRL, Crowthorne (UK), Kuntchen, J.M. Speed bumps cause ten times more pollution, AIT/FIA Traffic Commission, Munich, Nelson, P., Hickman, A. & Layfield, J. 77?f Environmental Assessment of Traffic Management Schemes, TRL (not published), Crowthorne (UK), 1995.