Helsinki Metropolitan Area Transportation System Plan 2020 was approved by the Helsinki Metropolitan Area Council (YTV) in 1994.
The main goals of the plan are to develop the transportation system in a coordinated way, to keep the share of public transport at the current level and to reduce the environmental impact of traffic.
The plan is currently being examined and in the inspection the environmental impacts are being evaluated in accordance with the principles of strategic environmental impact assessment. Evaluations have already been made in regard to air quality requirements. The air quality impacts of three different lines of action have been assessed on the basis of the present situation and three alternative transportation systems (car transport biased, public transport biased, and the transportation system approved in the 1994 plan) in the year 2020.
During the work, the CO, CO2, PM (particles), HC and NOx emissions have been estimated, the NO2 concentrations modelled using a state of the art dispersion model, and the exposure of the public to NO2 concentrations preliminarily evaluated. The location of the population during a weekday has been evaluated in 5 time periods.
The aim of assessing air quality effects has been to determine at the system level the air quality effects of different future transportation system alternatives.
At the same time, the study forms part of strategic EIA. According to Finnish EIA legislation the environmental impact of plans and programmes must also be assessed. The actual national instructions for strategic level assessment are in course of preparation.
Emissions calculation is a part of traditional EIA, but today it forms an insufficient viewpoint in order to evaluate the impacts of traffic system. It is essential to be aware also of the prevailing concentrations and exposure of the population. The NO2 concentrations and exposures were assessed because the NO2 concentrations continue to be fairly high during e.g. winter episodes. Exposure is a fundamental factor when examining the impacts of air pollution on health.
Particle concentrations are another air quality problem in the area, but there are no suitable methods for modelling particles available. In particular in the Helsinki Metropolitan Area modelling the so-called resuspension of street dust is difficult.
YTV is responsible for measuring air quality in the area and the real time measurement network in the area is comprehensive. Air quality is also on average rather good. Problematical components consist mainly of the high particulate concentrations and the periodical high nitrogen dioxide concentrations. The particulate concentrations are mainly caused by dust stirred up by vehicles, since in winter a lot of grit is spread on the streets and vehicles use studded tyres. Nitrogen dioxide concentrations increase especially during inversion situations in winter.
Air quality impacts were assessed in collaboration with the YTV's transportation department, the environmental office, the Technical Research Institute of Finland (VTT), and the Plan Centre Ltd. The work was directed by a group composed of regional and State experts, and led by an executive group. The executive group comprised representatives of those parties with decision-making power in transportation matters in the Helsinki Metropolitan Area.
The costs of the project were in the region of FIM 200,000. The project was mainly funded by the Ministry of Transport and Communications and YTV.
The results of the project will be benefited from when a decision is made on the final transportation system plan within the political organisations.
Nitrogen oxide, hydrocarbon, carbon monoxide, carbon dioxide and particulate emissions will decrease as a consequence of the development of vehicle technology, in spite of a growth in traffic in all the alternatives except for the car transport biased one, in which carbon dioxide emissions would grow by 7 % compared to the present level. The public transport biased alternative would bring lower emissions, with carbon dioxide emissions, for example, decreasing by 18 % compared to the present situation.
Air quality will also improve as emissions fall, but not, however, in direct proportion to all the components. For instance, most of the particulate matter concentration is caused by the resuspension of street dust, so that reducing direct emissions would not improve air quality to the same extent. Particulate concentrations may even increase with a growth in traffic. However, street dust is being actively combatted and the health effects are currently being studied.
Neither do nitrogen dioxide concentrations fall in proportion to emission reductions, as most of the nitrogen dioxide is formed in the atmosphere in reactions between different impurities. Exceedances of the national NO2 guideline concentrations (70 µg/m3, the second highest daily average during a month) were shown in small areas in central Helsinki even when assessed on the basis of the 2020 dispersion model calculations. The public transport alternative is the most favourable from the standpoint of its impact, but the differences between the various alternatives are rather small.
In the preliminary exposure study no great differences were detected between the different alternatives. The car transport alternative is the poorest alternatives, and the best is the alternative coinciding with the present transportation system plan. Its difference from the other alternatives is, however, slight. The public transport alternative is not the best because at the same time land use has been assumed to be more concentrated in the city centre area with its higher impurity concentrations. Remarkable, too, is the fact that exposure decreases at a markedly slower rate than NOx emissions do.
The emissions have also been calculated per person kilometres, and here the public transport is on average better than passenger cars fitted with catalytic converters in the future, too. In terms of some emission components a catalytic converter car is better, for example, than a bus.
The results of the work have been greeted with enthusiasm. There has been slight criticism of only a few assumptions. It is not possible for the time being to assess the significance of the results, as the inspection of the transportation system plan still remains to be completed.
Methods have been developed for evaluating air quality impacts. The vehicle mileage is being assessed by YTV using EMME/2 software.
The Technical Research Centre of Finland has estimated emission coefficients suitable for Finland's conditions. The Finnish Meteorological Institute has modelled NO2 concentrations with a dispersion model revolving in a super computer, which also takes into account chemical reactions. In addition, aside from traffic, impact from other sources is also taken into account in the results. Plan Center Ltd has modelled the location of population in 5 different time periods during a weekday. The concentration and exposure results have been output for 100m x 100 m squares and the emission results have been calculated in t/a.
At this point emissions, NO2 concentrations and exposures have been calculated once. In the future the emissions will be calculated again using the developed method when, e.g. land use estimates are more precise. However, NO2 concentrations will not be calculated afresh due to the high expense of calculation, and besides the direction of the changes in the various alternatives is clear. The exposure data will be studied in more detail, the factors, for example, that most influence the potential exposure of the population being analyzed.
No special problems arose during the work. The problems are mainly of the technical and scientific variety when complicated phenomena are represented by models. Additionally, the reliability of the initial data and assumptions selected play a central role.
The method can be applied in areas where sufficient initial data are available. Particularly essential are detailed traffic data for calculating emissions and concentrations. Similarly, modelling the location of the population calls for good initial data e.g. on housing and work places, as well as on the movement of people during the day.
The project indicated that through extensive cooperation, a broad assessment can be obtained of the air quality impacts of traffic. In an equivalent way, the effects could be evaluated also in the future or in other targets.
It was also possible for traffic and other statistical data collected for other purposes to be effectively benefited from in air quality impact assessments.
Good starting points and sophisticated model tools are, however, primary considerations for this kind of assessment.
Mr. Kari Hämekoski
Air Quality Research Scientist
Helsinki Metropolitan Area Council (YTV) PO Box 521
FIN-00521 Helsinki
Finland
fax: +358-9-1561 334
email: kari.hamekoski@ytv.fi
This has been developed by the city of Helsinki in collaboration with Rupprecht Consult, on behalf of the Car Free Cities network.