Traffic-related Emissions and Immissions 2009
Motor Vehicle Traffic Emissions Registry
The Motor Vehicle Traffic Emissions Registry was compiled anew on the basis of traffic counts for 2009, because according to experience to date, this category of polluters contributes significantly to particulate and nitrogen oxide pollution. Traffic counters have been installed at many locations on the primary roads of Berlin since 2001. This data serve to make the current traffic patterns in Berlin accessible, and to incorporate them into traffic management. This information is evaluated in the Office of Traffic Management (VKRZ), and is used to inform the populace (especially drivers) of traffic conditions and provide routing recommendations to avoid traffic jams via radio broadcasts, the internet, and centrally located sign boards.
Ascertainment of traffic volume
Since 2002, the data from approx. 400 detectors at about 300 locations within the Berlin primary road network have been available at the Traffic Control Office (VLB). Many of these detectors distinguish between cars and lorries, and can be used for approximate annual traffic counts.
In addition for 2009, traffic count figures for car, lorries, buses and motorcycles from an official count by trained persons at many intersections ordered approximately every 5 years by the Senate Department for Urban Development were available. Compared with counts by detectors, this official traffic count has the advantage of being better able to distinguish between lorries of more or less than 3.5 t, respectively, and other motor vehicles. For 2009 therefore, this traffic count was selected as the basis for the Emissions Survey for Motor Vehicle Traffic, 2009-2020, as had been the case for the previous Emissions Registers for Motor Vehicle Traffic in 1994, 1999 and 2005.
The exhaust emissions were then ascertained as follows:
- The extrapolation of the point-related intersection counts to the entire Berlin primary road network with a traffic-flow computational model (VISA) by the Senate Department for Urban Development provided the results showing the mean daily traffic figures (DTV) and the proportions of lorries for all major streets.
- The ascertainment of the segment-related pollution of the primary road network with regular bus traffic of the Berlin Transit Company (BVG) was calculated on the basis of the bus schedule data for 2009.
- The calculation of the emissions with the emission factors from the UBA manual for emissions factors (Edition 3.1, 2004) with consideration for the type of road and its function, was ascertained with the aid of the programme IMMISem/luft.
Ascertainment of emissions
The pollution emissions from motor vehicle traffic include exhaust and abrasion emissions from moving traffic, evaporation emissions from standing traffic, and evaporation emissions from fuel stations. Figure 2 provides an overview of the survey system. Emissions at fuel stations are assigned to “small business”.
The pollution and CO2 emissions from linear sources (primary roads) and area sources (secondary road networks and evaporation emissions) are calculated with the aid of emissions models.
The exhaust and abrasion emissions appear as linear sources on primary and secondary roads. However, they are only calculated as linear sources for the primary road network, because the aforementioned DTV traffic counts are only available for those streets. The emissions from the linear sources are then assigned to the grid network as area sources. The emissions from the secondary road network are, however, derived directly from estimates of traffic volume and lorry shares for each grid.
The primary roads (linear sources) and secondary road networks (area sources) emissions models
Exhaust emissions from motor vehicle traffic depend on factors which can be summarized as traffic-specific and motor vehicle-specific quanta.
Traffic-specific quanta are described by traffic density, i.e. the number of vehicles moving on a given section of a road (source), and their driving style (driving mode). Driving style is determined by street type (city centre street, secondary road, primary road with or without traffic lights, motorway), and function (shopping street, residential street, or access street).
The motor vehicle-specific quanta, generally expressed by exhaust emissions, are determined by:
- type of engine (four-stroke, two-stroke or diesel)
- type of carburetion (carburettor or fuel injection)
- type of fuel (two-stroke mixture, gasoline, diesel)
- type of purification system, if any (regulated or unregulated catalytic converter, recycling of exhaust gases); and
- other factors pertaining to the technical condition of the engine.
Emissions also depend on the driving style (driving mode), and are therefore stated for various driving styles. Cold weather starts, which lead to increased emissions during the warm-up phase of the engine, together with evaporation emissions, are considered important vehicle specific quanta.
The emissions factors are provided in the UBA Emissions Factors Manual (Version 3.1) for each year from 1990 through 2030. It lists the emissions factors for all relevant emitted substances for each vehicle group (passenger cars, light commercial vehicles, motorized two wheeled vehicles, buses, and heavy commercial vehicles), for currently at least five reduction levels (1980s ECE cycle, Euro 1, Euro 2, Euro 3, and Euro 4; Euro 5 only for heavy commercial vehicles), and for each type of road.
The stricter exhaust standard Euro 5 for cars is mandatory for new vehicles as of September 2009. However, the planned stricter standard Euro 6 for heavy commercial vehicles and Euro 6 for cars will very likely become effective only as of January 2013. These exhaust standards cannot be taken into account with the present version of the UBA manual, so that realistic forecasts for motor vehicle emissions are only possible through 2020.
Ascertainment of emissions from abrasion and resuspension caused by street traffic
With today’s knowledge, it is assumed that a large part of traffic related PM10 emissions do not originate from vehicle exhaust, but rather from the wind stirring up the particulate matter lying on the street surface, and from tyre and brake abrasion.
The calculations of these emissions with IMMISem/air are based on the modified EPA formula from corresponding investigations. This formula was developed from measurements taken on Schildhornstraße and on Frankfurter Allee, and is based on the finding that approx. 50% of the measured additional particulate in “canyon streets” in not attributable to motor vehicle exhaust, but is rather caused by motor vehicle related abrasion (braking and street/tyre abrasion) and resuspension. Since exhaust emissions have since been further reduced by improved engine technology, the proportion of additional pollution due to non-exhaust-caused emissions is today considerably higher than 50 %.
Figure 3 shows the various output quanta for the calculation of exhaust and abrasion emissions from traffic, such as driving style factors, “stop-and-go” add-on factors, cold weather start factors etc., as well as the results.
Emissions from motorized two wheeled vehicles cannot be shown due to a lack of traffic counts on the primary road network. Their contribution to the total is determined on the basis of the average traffic load in Germany, and available emissions data.
For areas with distinct orography, the road sections should be arranged in longitudinal categories. However, this is not necessary for Berlin.
Emission model for secondary roads networks (area sources)
The traffic pollution on secondary roads for 2009 was calculated with the aid of the traffic routing programme VISUM, based on the underlying source-goal relationship. The resulting total driving performance and the proportion of heavy commercial vehicles was assigned to the traffic cells in the city. The emissions in secondary roads from exhausts and from resuspension and abrasion were determined using the IMMISem/air emissions module.
In secondary roads networks, emissions are not calculated for specified sections of roads, but rather as 1 × 1 km grid squares. The driving performance for the grid squares is determined on the basis of:
- predominate use of the area, as either
- residential areas in the periphery;
- commercial and industry; or
- inner city and sub centres
- the number of residents and jobs is categorized as
- trade and service jobs, or
- the source/goal matrices of motor vehicle traffic derived from the above.
Further inputs for determining total emissions of each pollution component for each area correspond to those for the calculations in the primary roads network.
Exhaust and abrasion emissions in the city
Table 4 breaks down the driving activity caused by motor vehicle traffic in the city of Berlin (millions of vehicle kilometres per year); fuel use (t) and the exhaust and abrasion emissions of vehicular traffic (t/year), by type of vehicle, for the reference year 2009.
The new method of measuring emissions for this registry is also a suitable basis for dispersion calculations to determine the extent of pollution at streets. The extensive reorganisation of calculation methods permits only very limited comparisons with previous emissions increases, because these were based on a much simpler method of calculation.
Immissions – The results of stationary measurements
Street measurement stations are operated to ascertain the pollution caused by motor vehicle traffic, in the framework of the automatic air quality measurement network BLUME. In order to comply with EU Directives and the amendments to the BlmSchG and the 39th BlmSchV of 2010, resulting from those directives, revisions of the Berlin air quality measurement network are continually being carried out.
Since the concentrations of sulphur dioxide and carbon monoxide have now been reduced to only a fraction of the limit values, the measurement of these substances has been correspondingly reduced. Due to the current issues at hand, more attention is at the same time being directed towards the ascertainment of particulate matter (PM10) and nitrogen dioxide, particularly in the proximity of traffic.
For a detailed and complete online presentation of the long-term development of air pollution in Berlin, an archive has been established, which can be accessed via the Environmental Atlas Map “03.12 – Long-Term Development of Air Quality”.
Measurement of immissions in the municipal area
In 2010, air pollutant measurement was conducted at a total of 16 measurement containers (5 at the outskirts, 5 in the inner-city background and 6 at street locations), and at 23 RUBIS measurement stations. With these miniaturized devices, benzene and soot are collected as weekly samples. In addition, passive samplers were placed at these sites to measures nitrogen oxides. These devices collect samples during a sampling period of 14 days, which are then analyzed in the laboratory; for the locations of these measurement stations, see Figure 5. The exact addresses are listed in the monthly reports on air-pollution control of the Senate Department for Urban Development (only in German).
For the precise placement of sampling points and the implementation of the measurements, the following provisions of the 39th BImSchV are to be observed as closely as possible:
- The air flow around the measurement intake should not be impeded throughout a radius of at least 270°, and there should be no obstacles that could affect the air flow in the vicinity of the measurement station, i.e., buildings, balconies, trees or other obstacles should be several meters away, and the measurement stations for air quality at the building line must be at least 0.5 meters from the nearest building.
- Generally, the measurement intake should be placed between 1.5 m (breathing zone) and 4 m above the ground. Higher positions (up to 8 m) may be necessary under certain circumstances. A higher position may also be appropriate if the measurement station is to be representative for a larger area.
- The measurement intake should not be positioned in the immediate vicinity of any emissions source, so as to avoid the direct intake of emissions which have not been mixed into the ambient air.
- The exhaust outlet pipe must be positioned so that recirculation of exhaust air to the measurement intake is avoided.
- For all traffic-related pollutants, the sampling points should be at least 25 m from the edge of major junctions, and no more than 10 m from the kerbside.
The level of measured concentrations is not solely dependent on the number of motor vehicles and the resulting emissions, but also on the air exchange conditions, which are on the one hand determined by meteorological parameters (e.g. the wind), and on the other by the type and extent of buildings. Thus, there is a high immission impact registered in streets with buildings on both sides (“canyon streets”), such as on Silbersteinstraße in Neukölln, or Schildhornstraße in Steglitz, while lower pollution concentrations are found at the city motorway, which carries a noticeably higher traffic volume. Figure 6 shows typical pollution distribution in a canyon street. Such distribution develops if the wind direction (above roof level) leads from the measurement point towards the road, resulting in the formation of a turbulence in the canyon street. This blows the motor vehicle emissions to the side of the road where the measurement station is located.
Long-term trend of NO2 concentration in the municipal area
The results of the measurements carried out in 2010 throughout Berlin indicate the following long-term trend (cf. Figure 7):
- A clear drop in nitrogen dioxide concentrations was achieved around 1995 by equipping the Berlin power stations with denitrification facilities and the introduction of the regulated catalytic converters for gasoline-powered vehicles.
- NO2 pollution has hardly changed at all during the past ten years at any of the three station categories shown. The values of heavily-travelled streets (red curve) are still considerably above the EU annual average limit value of 40 µg/cu.m.
- The expected reduction in nitrogen oxide emissions due to the improvement in exhaust gas technology in vehicles has not included any reduction in nitrogen dioxide pollution.
Long-term trend of PM10 concentration in the municipal area
Figure 8 shows the development of PM10 and total particulate concentrations in Berlin and the surrounding areas over the past more than 20 years (in 1997, the measurement system was changed from overall dust to particulates [PM10]).
The red curve shows pollution at three measurement stations near traffic, while the blue and dark green lines show the concentrations at three measurement stations in populated areas of the inner city, and at five measurement points on the outskirts of the city.
A comparison of the curves reveals the following noteworthy points:
- The PM10 concentrations on the outskirts of Berlin and in the rural areas of Brandenburg around the city had by 2003 already reached approx. half the PM10 pollution level on major Berlin inner-city streets. By 2010, due to a continual annual mean drop in concentrations in the traffic sector, the ratio between the outskirts and the major inner-city streets then settled at approx. 2:3.
- The drop in particulate values which continued throughout the ‘90s has not continued during the past few years. By contrast, the soot pollution level on major streets declined continuously from 1998 to 2004, by almost 40 %, one cause being the improvements in exhaust gas technology in the vehicles, including those of the bus fleet of the Berlin Transport Company (BVG).
- The annual mean for fine particle pollution near traffic has since 2004 been below the EU limit of 40 µg/cu.m. However, before 2006 and after 2009, the more stringent 24-hour limit was exceeded on some occasions. The 24-hour limit of 50 µg/cu.m. is not to be exceeded more than 35 times per calendar year. The decrease in the annual mean value and the number of exceedance days in 2007 and 2008 is also attributable to favourable meteorological conditions, and to the establishment of the Environmental Zone. In 2010, the number of exceedance days above 50 µg/cu.m. would have been higher by about 10 days without the Environmental Zone.
- The annual variation of PM10 levels is similar at all stations. In particular, the clear resurgence of PM10 levels in 2002, 2003, 2005, 2006 and since 2008 is a phenomenon that has appeared at the same time throughout the city, as well as at stations located on the outskirts of the city. The cause is hence not primarily to be found in Berlin’s PM10 emissions; but is rather attributable to unfavourable weather conditions (a large number of wintertime low-exchange southerly and south-easterly wind situations) and the large-scale transport of particulate matter.