Berlin Environmental Atlas

03.11 Traffic-Related Emissions and Immissions (Edition 2011)

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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.

Figure 3
Fig. 3: Emission model for the calculation of quantities of emitted pollutants on primary road (Liwicki, Garben 1993)

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)

Figure 4
Fig. 4: EM-NEBEN – Emissions model for the secondary roads networks (area sources) (Liwicki, Garben 1993)

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 x 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
    • manufacturing
  • 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.

Table 4 - Dummy
[Approx. 36 KB size.]

Tab. 4: Traffic volume (in millions of vehicle-km/year), fuel consumption (t) and exhaust and abrasion emissions (t/year) in the municipal area of Berlin, by type of vehicle; Reference year: 2009

[Table is also available as Excel-File (MS-Excel is required).]

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.

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