ARTICLE IN PRESS
Atmospheric Environment ] (]]]]) ]]]–]]]
www.elsevier.com/locate/atmosenv
BAB II: a project to evaluate the accuracy of real-world traffic
emissions for a motorway
U. Corsmeier, M. Kohler, B. Vogel, H. Vogel, F. Fiedler
Institut für Meteorologie und Klimaforschung, Forschungszentrum Karlsruhe/Universität Karlsruhe, Postfach 3640,
76021 Karlsruhe, Germany
Received 22 March 2004; received in revised form 10 August 2004; accepted 20 August 2004
Abstract
To ensure the efficiency of strategies to reduce air pollutants caused by road traffic, it is essential to evaluate the
emission data to be used in emission calculation models. This basic approach of the BAB II project
(BundesAutoBahn––federal highway) has been reached by simultaneous measurements of gaseous and particulate
emissions on the windward and lee side perpendicular to a motorway. The differences between the measurements allows
for the calculation of the emissions caused by traffic on the motorway. Measurements of CO, NO, NOx, CO2, O3, VOC,
and particulates of high horizontal and vertical resolution were made. The experimental setup was made symmetric to
the motorway, with 52 m high towers on each side. The field phase took place from 1 to 25 May 2001 at the motorway
A656 near Heidelberg, Germany. In cases of wind direction perpendicular to the motorway, the height of the plume
caused by traffic emissions is detectable and the emissions released on the motorway can be calculated. With traffic
census carried out simultaneously, the emission data can be estimated using emission factors given in the literature.
Comparison between real-world traffic emissions and calculated emissions allows for an evaluation of the emissions
calculated by the models.
This paper gives an overview of BAB II, its measuring concept, the experimental setup, and the quality assurance and
control program. It is shown in detail that the method of emission estimation by measurements of concentration
differences between both sides of a motorway works quite well if the meteorological assumptions for determining realworld traffic emissions have been fulfilled. Detailed results in terms of measured and model-calculated emissions of
gaseous and particulate species will be reported in a number of subsequent papers.
r 2004 Elsevier Ltd. All rights reserved.
Keywords: Real-world traffic emissions; Emission calculation model; Traffic census; Evaluation strategy; Particulate matter
1. Introduction
For the evaluation of the success of strategies to
reduce the emissions of road traffic, heating, and
Corresponding
author.
Tel.:+49 7247 822843;
+49 7247 824377.
E-mail address: [email protected]
(U. Corsmeier).
fax:
industry, these have to be measured. Motor vehicle
emissions play an important role in air pollution.
Among others, they contain nitric oxide, carbon
monoxide, sulfur dioxide, hydrocarbons, and
particulate matter (PM) like diesel soot. Following
chemical transformation, some species may cause
high ozone concentrations during summer. Very
small aerosol particles incorporated by respiration
are suspected to be injurious to health. Additionally,
1352-2310/$ - see front matter r 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.atmosenv.2004.08.056
ARTICLE IN PRESS
2
U. Corsmeier et al. / Atmospheric Environment ] (]]]]) ]]]–]]]
they act on the climate system and contribute to the
greenhouse effect.
Numerical simulations represent a major tool in the
development of emission reduction strategies to prevent
episodes of high air pollution. The model simulations
serve to study the effects of varying emissions and
meteorological conditions on the concentration distributions of primary vehicle emissions and their consecutive products (Simpson, 1992; Vogel et al., 1995;
Memmesheimer et al., 1996). Model calculations allow
the determination of the future load of the atmosphere.
Emission data are major input variables of the models.
It is necessary to provide reliable data on the emission
situation. In the past, considerable progress was
achieved concerning the degree of detailing of calculations of anthropogenic emissions of ozone precursors
and other gaseous pollutants (Obermeier et al., 1995;
Wickert et al., 1998; Olivier and Berdowski, 2001).
However, less is known about the emissions of PM, such
as soot, its mass concentrations, particle size distributions and aging processes (Lazaridis et al., 2000).
Road traffic is the main contributor to the total
anthropogenic emissions of nitrogen oxides (NOx),
carbon monoxide (CO), and PM, especially soot. In
Germany, the contribution of traffic to the total
anthropogenic emissions in 2002 reached 58% for NOx,
59% for CO, and 20% for non-methane hydrocarbons
(NMHC) (Umweltbundesamt (UBA), 2004). While the
contribution of road traffic to the overall PM emissions is
66%, nearly 100% of the soot is emitted by road traffic.
Former emission measurements were often restricted to
tunnel studies. The emissions were determined from the
difference of gas fluxes at the entrance and the exit of the
tunnel (Weingartner et al., 1997). Pierson et al. (1996)
summarized the results of two tunnel studies performed
in the US. They found that observed and modeled
gaseous emissions agreed within 50% for most of the
time. Another tunnel study was performed in Switzerland
near Zurich by Staehelin et al. (1995). Here, the
concentrations of air constituents were measured and
parallel traffic counts were performed. Emission factors
were determined for passenger cars as well as for heavyduty (HDV) and light-duty vehicles (LDV). Emission
factors of LDV calculated from long-term measurements
of 23 NMHCs in the Kiesberg tunnel in Wuppertal,
Germany, were published by Gomes et al. (2004). For
most of the NMHCs, significantly higher concentrations
were found in the Kiesberg tunnel, although this study
was the latest one and emission reduction technology
incorporated in the vehicles should have been up to date.
Decadal comparisons of emissions in the Tauerntunnel
(Austria) are given by Schmid et al. (2001). Between 1988
and 1997, CO and hydrocarbon were reduced by 90%,
PM by 20%, but NOx emissions increased by 20%.
The advantage of the tunnel studies is that they are
dealing with well-defined volumes of air. However, a
major problem that applies to all one-way tunnels was
identified to be the air flow of up to 30 km h1 in the
tunnel tube, which was mainly caused by trucks.
Consequently, the driving resistance of the passenger
cars changes and, thus, the emission behavior no longer
corresponds to that of vehicles operated in free air.
Zhang et al. (1995) used a remote sensing technique to
determine the relative CO and VOC emissions of about
1 million cars at 22 different locations all over the world.
A disadvantage of the method is that absolute emissions
can only be determined if the average fuel consumption
is known. The study shows that a small percentage of
cars (7% in case of Hamburg and 25% in case of
Kathmandu) caused 50% of the total emissions of CO.
De Vlieger (1997) measured the tailpipe emissions of six
different cars equipped with three-way catalytic converters and one carburetted car without catalytic
converter using an on-board measuring system under
different driving cycles. One major finding was the
importance of the cold-start emissions in case of CO and
hydrocarbons. She also found that a low-emission car
when subjected to a chassis dynamometer test does not
necessarily produce low emissions in real traffic situations. The advantage of on-board measurements is that
errors due to flux measurements necessary in tunnel and
free-air studies are avoided, while the disadvantage is the
expensive technical equipment necessary to measure the
vehicles. The efficiency of a controlled three-way
catalytic converter in a passenger car was investigated
by Heeb et al. (2000). When operated in standard
driving cycles, the emission reduction efficiency for
benzene, toluene, and xylene (BTX) is satisfactory only
in a velocity range of 60–120 km h1. When driving
faster than 130 km h1, more benzene and toluene were
formed than without an exhaust gas treatment by a
catalytic converter system.
Free-air measurements by Leisen et al. (1992) were
carried out at a motorway in Germany. Towers were
erected very close to the motorway on both sides. Using
such a setup to determine emissions, theoretical investigations of Wenzel (1998) show that the contribution of
turbulent fluxes to the overall mass flux is in the order of
20%. An error of the same magnitude results when
determining the emissions. This problem can be solved
by measuring the turbulent fluxes in addition to the
mean fluxes.
In the former BAB 656 study by Vogel et al. (2000),
the method of checking the accuracy of model-calculated emissions using real-world measurements of trace
gas concentration differences between the lee and the
windward sides of the motorway was tested. The
deficiencies of BAB 656 consisted in the estimation of
the CO and NOx plume height using O3 as indicator and
in comparing measured and calculated emissions for
three 1-h intervals only. PM and atmospheric turbulence
were not measured during BAB 656.
ARTICLE IN PRESS
U. Corsmeier et al. / Atmospheric Environment ] (]]]]) ]]]–]]]
2. The BAB II concept
In general, the measurement concept is based on the
assumption of homogeneous conditions for all parameters along the respective road section (Vogel et al.,
2000). In this case, the emissions caused by the road
section can be determined by the following equation:
Zh
Qi ¼
v? ðzÞððci ðx2 ; zÞ ci ðx1 ; zÞÞdz;
(1)
0
where Qi and ci are the source strength and the
concentration of the substance i; respectively, v? is the
wind velocity perpendicular to the road, and h denotes
the vertical extension of the exhaust gas plume at the
position x2 : The position x1 is located on the windward
side, the position x2 on the lee of the road (Fig. 1). Using
Eq. (1), we assume that no deposition and no chemical
transformations take place between x1 and x2 : Furthermore, it is assumed that v? only depends on the vertical
v
h
z
As there are indications that traffic-induced turbulence is important to the dispersion and dilution of
emissions close to the source (Chock, 1980; Eskridge
and Thomson, 1982; Eskridge and Rao, 1983; Rao et al.,
2002), horizontal and vertical profiles of turbulence were
measured in BAB II (BundesAutoBahn––federal highway). In parallel, a traffic census was made to evaluate
the model input data, to calculate emissions using realworld traffic data, and to compare detailed traffic data
with those from automatic counters. Additionally, the
traffic census was used to check whether the predictions
made by the German UBA (Environmental Protection
Agency) in 1997 with respect to the degree of exhaust
gas reduction technologies used in the vehicle fleet had
come true (UBA, 1999). The quality of the measurements was controlled by an independent quality
assurance (QA) program.
This paper focuses on the verification of the method
of emission estimation by measurements of concentration differences between both sides of a motorway under
varying meteorological conditions for determining realworld traffic emissions in cases of wind perpendicular to
the line source. A project with a similar approach of
emission calculation and evaluation has been successfully conducted around the German city Augsburg in
1998 by Slemr et al. (2002). Here, the emissions of a
whole city have first been estimated using ground-based
and airborne instrumentation at the lee and windward
side of the city (Kalthoff et al., 2002) and finally
compared to model-calculated emissions (Kühlwein et
al., 2002). Furthermore, it is the purpose of this paper to
give an overview of the BAB II objectives, its measuring
concept, its experimental setup, and the available data.
3
x1
x2
x
Fig. 1. Sketch of the BAB II concept, indicating the exhaust gas
plume height h, the points of measurements x1;2 ; and the wind
direction v.
coordinate and that the turbulent fluxes can be neglected
as compared to advection. In addition, stationary
conditions are assumed. It follows from Eq. (1) that
the variables v? ðzÞ; ci ðx; zÞ; and h have to be measured to
obtain the source strength of the motorway. The
assumption of small turbulent fluxes compared to the
mean fluxes is incorrect when the mean wind blows
parallel to the motorway or when the mean wind speed
is very low. Under these circumstances, it is not possible
to determine the emissions using Eq. (1).
The BAB II concept includes symmetric, continuous
profile measurements of several exhaust gases and PM.
Diurnal cycles of vertical and horizontal profiles of NO,
NOx, CO, CO2, O3, and VOC as well as of PM,
especially soot, were measured with a high temporal and
spatial resolution on both sides of a motorway section
with dense traffic. In addition, vertical profiles of the
meteorological parameters of wind speed, temperature,
and humidity were measured. The vertical extension h of
the plume was determined by the vertical profiles of CO
and NOx. Ozone concentration profiles were used to
check the validity of the plume height, since the titration
effect of the emitted NO caused a decrease of the ozone
concentration within the plume.
A detailed traffic census, taking into account the
different layers of vehicles, was carried out by Kühlwein
and Friedrich (2005). Using an emission calculation
model, statistical traffic data, and the traffic census
results, finally the calculated emissions are evaluated by
the measured emissions.
3. Experimental design
3.1. Location and time window
The measurements were carried out from 1 to 25 May
2001 at the motorway A 656 from Heidelberg to
ARTICLE IN PRESS
4
U. Corsmeier et al. / Atmospheric Environment ] (]]]]) ]]]–]]]
Fig. 2. Map of the BAB II investigation area on both sides of the motorway A 656 from Heidelberg to Mannheim.
Mannheim, Germany, about 1.5 km west of the Heidelberg motorway interchange (Fig. 2). Due to channelling
in the Rhine Valley, southwesterly or northeasterly
winds are prevailing in the area. The motorway is
directed straight from southeast to northwest
(1351–3151) and, hence, located perpendicular to the
expected main wind direction. It runs on a 1 m high,
grass-covered embankment. The terrain near the motorway is flat and subject to agricultural use. During the
field phase, 30–60 cm high wheat was cultivated north of
the motorway on the field in the east of the measurement
line. On the field in the west, 10–30 cm high green fodder
was grown. South of the motorway, 30–60 cm high
wheat was cultivated. The area far west and south of the
measurement line was covered with bare soil (Figs. 3 and
4). The only obstacles for air flow were two bridges
crossing the motorway about 400 m southeast of the
measurement line and 700 m in northwesterly direction.
Additionally, six small farm houses are located about
500–1000 m northeast of the measurement field.
The measurements were performed along a 212 m line
northeast and along an 84 m line southwest of the
motorway. The width of the motorway itself is 35 m. The
two measuring lines are shifted 140 m to the southeast
when crossing the motorway (Fig. 3). During the entire
campaign of 25 days, most of the measurement systems
were operated continuously. The measurement systems
placed in the tower elevators and the VOC sampling
systems were run during seven special observation
periods (SOPs) (Table 1). The time is given in Central
European Summer Time (CEST).
3.2. Measurement setup
As seen from Figs. 3 and 4, the main components of
the measuring lines were two 52 m high towers: PS2,
south of the motorway at a distance of 84 m, and PN2,
60 m in the north. They were equipped with sensors that
continuously measured meteorological and chemical
parameters at 10 heights each and elevators for profiling
gas and particle concentrations during the SOPs. Nearsurface concentrations of the exhaust gases NO, NO2,
CO, CO2, 26 VOCs, and O3 as well as particle size
distributions, the chemical composition of aerosols, and
the total volume of PM were measured at different
distances from the motorway along the lines. South of
the motorway, these measurements were made at point
PS2 (tower basement, 84 m south) and PS1 (10 m south).
In the northern section, the instruments were installed at
PN1 (10 m north), PN2 (tower basement, 60 m north),
and PN3 (80 m north). A SODAR was located 212 m
away from the motorway at the northern edge of the
line.
Mini towers, 4.5 m each, with instrumentation for the
measurement of turbulent fluctuations of wind, temperature, and humidity were mounted at T1 (3 m south),
T2 (3 m north), T3 (30 m north), T4 (50 m north), and
T8 (90 m north). At T8, the surface energy budget and
precipitation were measured. Additionally, the tower
PN2 was equipped with instrumentation of the mini
towers in vertical direction at the levels of 18, 33, and
48 m. Two DOAS systems were operated on the bridge
embankment northwest of the site at distances of 700 m
ARTICLE IN PRESS
U. Corsmeier et al. / Atmospheric Environment ] (]]]]) ]]]–]]]
5
Fig. 3. Layout of the 1.1 km wide BAB II measurement site between two bridges crossing the A 656, embedded in flat agriculturally
used land. Tower PS2, surface station PS1, and mini tower T1 depict the southern part of the measuring line, mini towers T2–T8,
surface stations PN1, PN3, tower PN2 and the SODAR represent the northern part.
Fig. 4. Measuring line seen from the bridge in the southeast. Tower PS2 is on the left, tower PN2 on the right. The traffic census was
done from the bridge in the background.
from tower PN2 and 840 m from tower PS2, respectively
(Fig. 3). The light paths were directed to four reflectors
on both towers at 10, 20, 30, and 40 m height (i) parallel
to the motorway and (ii) in the cross mode. Traffic
census was done during the SOPs and additional time
intervals on the bridge in the northwest.
ARTICLE IN PRESS
U. Corsmeier et al. / Atmospheric Environment ] (]]]]) ]]]–]]]
6
Table 1
BAB II special observation periods (SOPs)
SOP No.
1
2
3
4
5
6
7
Day
Tuesday/Wednesday
Monday/Tuesday
Tuesday/Wednesday
Sunday/Monday
Wednesday/Thursday
Friday
Wednesday/Thursday
Begin SOP
End SOP
Date
Time CEST
Date
Time CEST
01
07
08
13
16
18
23
20:00
20:00
20:00
20:00
14:00
06:00
20:00
02
08
09
14
17
18
24
20:00
20:00
20:00
20:00
22:00
22:00
20:00
May
May
May
May
May
May
May
May
May
May
May
May
May
May
01 May (Tuesday) and 24 May (Thursday) were holidays in Germany in 2001. This means changes in traffic density compared to
normal working days.
Fig. 5. Meteorological instrumentation installed at the towers and surface stations: T (temperature), T F (wet bulb temperature), WS
(wind speed), WD (wind direction), u; v; w (wind speed components), NN (precipitation), S (south of motorway), N (north of
motorway). For details see text.
3.2.1. Meteorological measurements
Considerable meteorological measurements were
made in a y2z plane perpendicular to the motorway
(Fig. 5). At PS2 and PN2, vertical profiles of temperature T; wet bulb temperature T F ; using PT 100
instruments, and wind speed WS, using cup anemometers were measured at six heights. Wind direction
WD was recorded by wind vanes at the towers’ tops. On
the ground, horizontal profiles of T; T F ; WS, and WD
were collected at points PS1 at 6 m height in the south
and PN2 (6 m) and PN3 (6 m) in the north. PT 100
thermometers, cup anemometers, and wind vanes were
used. Ten minute averages were calculated. The SODAR
measured vertical wind profiles (WS, WD) up to an
altitude of 600 m at the northern edge of the line.
Turbulent fluctuations of temperature, humidity, and
wind were measured by fast PT 100 sensors, dew point
mirrors, and sonic anemometers at 4.75 m height at the
top of the towers T1–T4 and at T8 (Fig. 3). Vertical
turbulence profiles were recorded at PN2 at the points
T5 (18 m height), T6 (33 m), and T7 (48 m) using the
same instruments. The sampling frequency for the
turbulence measurements was 20 Hz. At T8, the surface
energy budget, including the long-wave and short-wave
ARTICLE IN PRESS
U. Corsmeier et al. / Atmospheric Environment ] (]]]]) ]]]–]]]
radiation balance, soil heat flux, sensible and latent heat
fluxes were measured (Kalthoff et al., 1991). The
meteorological data were gathered over the entire BAB
II field phase.
3.2.2. Continuous gas measurements
Both towers were equipped with 10 air intakes
between 8 and 51 m height (Fig. 6). Via individual
Teflon tubes the inlets were connected to gas analyzers
at the tower’s basement. Bypass pumps were used to
maintain a constant, fast air flow in each tube. The
mixing ratios of NO and NOx were determined by
Monitor Labs 9841A analyzers. Those of CO were
recorded by Aero Laser AL5001 monitors and CO2 was
measured by two BINOS-IR-photometric instruments.
NO, NOx, CO and CO2 were measured at each level for
3 min, starting at 8 m height. Monitor Labs and Aero
Laser instruments were operated for the whole field
phase with the exception of calibration intervals of
about 1 h before and after each SOP. The CO2
instruments were used during the SOPs within the tower
elevators. Additionally, O3 was recorded on each tower
using six Environnement 41 M monitors. These instruments were operated permanently during the whole
campaign with 10 min mean values being taken. Emissions and emission factors calculated from the concentration differences are given by Kohler et al. (2005).
During the SOPs (Table 1), vertical profiles of NO,
NO2, CO2, and O3 were measured by operating both
elevators synchronously in the continuous mode. The
7
elevator speed was 10 m per minute. Measurement of
each profile took about 5 min, and after 3–6 h the
analyzers were recalibrated. The instruments used are
described by Vogt et al. (2005).
On the ground, horizontal profiles of the abovementioned gases were recorded between 4 and 6 m
height at PS1, PN1, PN2, and PN3. The monitors in use
at the four sites, their principles of measurement, their
detection limits, and the accuracy of the measurements
are given in Table 2. All gas measurements are 10 min
mean values as well as the meteorological parameters.
The DOAS systems were used to measure vertical
profiles of NO, NO2, O3, and SO2 averaged over 700 and
840 m distance between the embankment and the towers.
At both towers, vertical profiles were taken within 8 min
(v. Friedeburg et al., 2005).
3.2.3. VOC measurements during SOPs
Draeger adsorption tubes were employed for sampling
VOC compounds, including BTX, over 1–3 h depending
on traffic density during SOPs at six levels (4, 18, 28, 33,
38, and 48 m) on the lee side tower and at three levels (4,
28, and 38 m) on the windward tower, respectively.
Quantitative analyses of individual VOCs were performed in the laboratory by means of gas chromatography with flame ionisation detector (GC-FID). Details
of sampling and data analysis are given by Vogt et al.
(2005). At the basement of both towers, Airmovoc 2010
instruments were installed for continuous analysis of
26 VOC components during the SOPs. The VOC
Fig. 6. Instrumentation used to analyze the gases CO, CO2, NO, NOx, O3, and SO2 at the towers PS2 and PN2 (including elevators)
and at surface stations PS1, PN1, PN2, and PN3. The analyzers and their modes of operation are described in the text.
ARTICLE IN PRESS
U. Corsmeier et al. / Atmospheric Environment ] (]]]]) ]]]–]]]
8
Table 2
Analyzer characteristics and trace gas measurements of CO, CO2, NO, NO2/NOx, O3, and SO2 recorded between 4 and 6 m height at
PS1, PN1, PN2, and PN3
Site
Gas
Monitor
Measurement principle
Detection limit
PS1
CO
NO
NOx
O3
CO2
NO
NOx
MLU
MonitorLabs or TE425
Thermo Environmental
Bendix +TE UV
Airmotec
NO Analyzer CLD AL 770 ppt
and photolytic converter PLC
760 (ECO-Physics)
Ozone monitor, model 1009-CP
dasibi, or ozone analyzer,
model 49C Thermo
Environmental Instruments
Inc.
MLU
MLU
NDIR
Chemiluminescence
50 ppb
1 ppb
Chemiluminescence+UV
Gas chromatography
Chemiluminescence
1 ppb
10 ppmV
710%
o15 pptV (600 s integration), o50 pptV (30 s
integration), resp., 710%
UV absorption
1 ppbV (49C)
75% (49C)
PN1
O3
PN2
PN3
CO
NO
NOx
O3
NO
NOx
O3
SO2
Accuracy
NDIR
Chemiluminescence
MLU
APNA 360 Horiba
UV absorption
Chemiluminescence
0.0005 ppm
710%
APOA 360 Horiba
APSA 350 E Horiba
UV absorption
UV fluorescence
0.0005 ppm
0.002 ppm
710%
710%
compounds are reported by Petrea et al. (2005). Prior to
and after each SOP, the Airmovoc 2010 devices were
calibrated using a certified calibration gas of 30 VOC
components. At PN3 (Fig. 3), BTX was detected by an
Airmovoc 1010 during the whole field phase. This
instrument was calibrated automatically. Remote sensing of VOC was made by the DOAS systems on both
sides of the motorway up to 13 May. Details of DOASVOC detection are given in Pundt et al. (2005).
3.2.4. Measurements of particulate matter
The equipment measuring properties of particulate
atmospheric aerosol was operated continuously during
the field phase, except for the elevator instrumentation
operated during SOPs only (Fig. 7). The tower PS2 was
equipped with two scanning mobility particle sizers
(SMPS) for scanning particle sizes between 10 and
700 nm, while tower PN2 carried three SMPS. Optical
particle counters (OPC) measuring particles sizes in 15
classes between 0.3 and 20 mm were installed at one level
and temporarely mounted in the elevators during the
SOPs. In the lee side elevator, an electrostatic lowpressure impactor (ELPI, detection range 0.03 –10 mm)
and a diffusion charger (DC) were in use during the
SOPs. Highly resolved vertical size distributions of PM
were measured by the ELPI, which clearly indicate the
plume height. In the PS2 and PN2 basements, the mass
of particles below 1 mm diameter was detected by PM1
and below 10 mm by PM10 instruments and averaged
over 30 min. Black carbon (BC, averaged over 5 min), in
particular soot, was recorded by aethalometers at the
same place. The particle number, particle size distribution, particle mass, and composition of particles were
detected by OPC, EC/OC, aerodynamic particle sizer
(APS, size range 0.2–10 mm), PARTISOL (PM 2.5 and
PM 10), and TEOM (PM 2.5 and PM 10) instruments at
the PN2 basement. Elemental and organic carbon (EC/
OC) was measured at PS1. In addition, particulate
matter PM10 was retained in filters of the low-volume
sampler (LVS) at PS2, PS1, and PN2. The filters were
replaced after 24 h and analyzed at the laboratory. As
the plume height and differences in particle mass and
size distribution could be detected between the windward and lee sides, particle emission by traffic could be
estimated (Imhof et al., 2005; Rosenbohm et al., 2005).
3.3. Quality assurance, traffic census, and emission model
The BAB II QA program for gas and aerosol
measurements, including measurement of certified calibration gases and ambient air measurements, was
implemented by an independent group from the University of Stuttgart, according to procedures given in
Kanter et al. (2002). The concentrations of the calibration gases were checked at certified laboratories.
Correction coefficients and equations were calculated
ARTICLE IN PRESS
U. Corsmeier et al. / Atmospheric Environment ] (]]]]) ]]]–]]]
9
Fig. 7. Instrumentation measuring PM: at the towers SMPS and OPC; in the elevators an ELPI and a DC at the lee side as well as
OPCs at both sides. EC/OC was measured at PS1. At the tower basements particle number, particle size distribution, particle mass, and
kind of particles were detected by OPC, EC/OC, PM1, PM10, BC, APS, SMPS, PARTISOL, and TEOM instruments. LVSs for PM10
were operated at PS2, PS1, and PN2. For details see text and Imhof et al. (2005) and Rosenbohm et al. (2005).
for the instruments and applied to the data. Details of
the QA procedures, the harmonization of the instruments and the remaining measurement uncertainties are
given in Vogt et al. (2005).
Traffic characteristics were recorded during most of
the SOP time and during additional intervals at the
measurement lines and at the automatic traffic test port
at a motorway exit northwest of the measurement lines.
The traffic samples taken during the SOPs could be used
to update the data collected at the automatic test port,
getting representative traffic data for the whole BAB II
period. License plate numbers, recorded with a video
camera, were compared with the central vehicle register
of the German Kraftfahrtbundesamt (Federal Traffic
Agency) that provided vehicle-specific data in anonymous form. The information about vehicle category,
engine type, cubic capacity, and date of registration
allowed to assign the registered vehicles to 82 vehicle
layers as defined in the emission factor handbook (UBA,
1999). For traffic census results see Kühlwein and
Friedrich (2005).
Different sets of emission data were calculated using
the model of John (1999) and applying the three stages
of model improvements by Kühlwein and Friedrich
(2005) based on BAB II data. The model is based on
high-resolution input parameters. The degree of resolution in calculating emissions from road transport is
determined by the degree of disaggregation of the
emission factors available. The best emission factors
available are disaggregated in vehicle layers and typical
driving patterns. Correction factors exist for cold-start
surcharges, road grade, and vehicle loadings (UBA,
1999). Normally, the essential traffic parameters cannot
be obtained by measurements. Hence, statistical data of
traffic volume, car fleet composition, and mean driving
pattern distributions are taken for emission modeling.
Based on such data, first a pre-calculation of emissions
was made, while finally the actual traffic census data
were used to update the emission calculations and to
compare measured and calculated emissions (Corsmeier
et al., 2005).
4. The BAB II field phase
The crucial point in calculating source intensities from
measurements of real-world emissions is the validity of
the meteorological requirements for the method, i.e.
wind blowing perpendicular to the motorway and
stationary and homogeneous conditions. This is documented by Fig. 8 which shows wind speed and wind
direction during the field phase. Because of the
variability of the wind direction, sectors of 7451 with
respect to the perpendicular approaching flow were
tolerated. The motorway is directed from 1351 to 3151.
Thus, differences of vertical trace gas and particle
concentration profiles can be calculated if the wind
ARTICLE IN PRESS
U. Corsmeier et al. / Atmospheric Environment ] (]]]]) ]]]–]]]
10
315
8
270
7
225
6
180
5
135
4
3
90
2
45
1
0
3
4
5
6
7
8
9
360
12
11
10
9
8
7
6
5
4
3
2
1
0
315
270
225
180
135
90
45
0
9
WS in ms-1
2
WD in degrees
WS in ms-1
1
10
11
12
13
14
15
16
17
12
11
10
9
8
7
6
5
4
3
2
1
0
360
315
270
225
180
135
WD in degrees
WS in ms-1
9
WD in degrees
360
10
90
45
0
17
18
19
20
21
22
23
24
25
May 2001
Fig. 8. Time series of wind speed (WS, solid line) and wind direction (WD, dotted line) from 1 to 25 May 2001. Horizontally shaded
areas indicate wind directions approximately perpendicular to the motorway (01–901 and 1801–2701), while dark shaded areas indicate
predominantly valid wind directions during SOPs.
comes from the sectors of 01–901 and 1801–2701. These
sectors are horizontally shaded in Fig. 8. Beginning and
end of the SOPs are marked by vertical lines, indicating
the intervals of elevator operation at the towers. The
wind speed on 2, 8, 9, 14, and 24 May was mostly below
4 m s1. During these SOPs, high-pressure situations
over Europe with few cumulus clouds, high incoming
radiation, and mixing conditions during the day as well
as stable stratification at night prevailed. In the SOPs on
17 and 18 May a stronger southwesterly flow in front of
a western European trough accompanied by overcast
sky and some rain was observed when a cold front
passed the area.
Table 3 summarizes the BAB II periods with
the conditions for estimating source intensities using
lee–windward differences being fulfilled. Time periods
ARTICLE IN PRESS
U. Corsmeier et al. / Atmospheric Environment ] (]]]]) ]]]–]]]
11
Table 3
BAB II periods with the conditions for estimating source intensities being fulfilled: wind from sectors 01–901 or 1801–2701 and CO
concentration differences 420 ppb between the lowest and uppermost measuring level on the lee side and NOx differences 45 ppb,
respectively, traffic density 41000 vehicles per hour, minimum interval length 3 h during SOPs and 4 h during other times
Wind direction
Day
Begin CEST
End CEST
Duration
South
South
South
South
South
South
South
South
North
North
North
North
North
North
North
North
North
North
North
North
Thursday
Friday
Tuesday
Monday
Tuesday
Wednesday
Thursday
Friday
Wednesday
Wednesday
Saturday
Sunday
Monday
Tuesday
Thursday
Friday
Monday
Tuesday
Wednesday
Friday
03
04
08
14
15
16
17
18
02
02
05
06
07
08
10
11
21
22
23
25
03
04
08
14
15
16
18
19
02
02
05
06
07
08
10
12
21
22
23
25
13
6
4
14
14
4
14
14
2
3
14
8
14
4
6
11
13
14
5
4
May
May
May
May
May
May
May
May
May
May
May
May
May
May
May
May
May
May
May
May
07:00
06:00
16:00
06:00
06:00
06:00
06:00
06:00
06:00
16:00
06:00
12:00
06:00
06:00
06:00
09:00
06:00
06:00
06:00
06:00
May
May
May
May
May
May
May
May
May
May
May
May
May
May
May
May
May
May
May
May
20:00
12:00
20:00
20:00
20:00
10:00
20:00
20:00
08:00
19:00
20:00
20:00
20:00
10:00
12:00
20:00
19:00
20:00
11:00
10:00
Precipitation
O
O
O
Intervals within SOPs are in bold. Nighttime intervals between 20 and 06 CEST are excluded due to stable stratification of the PBL.
with less than 1000 vehicles per hour passing the
measuring line were excluded. In most cases, such
periods occurred between midnight and 06 CEST on
working days and between 00 and 08 CEST on Sundays.
Additionally, only those vertical profiles of continuous
gas measurements were taken into account, where CO
concentration differences were 420 ppb between the
lowest and uppermost measuring level at the lee side and
NOx differences were 45 ppb for a time period of at
least 3 h. The model-based source intensity calculations
were performed between 06 and 20 CEST. Altogether,
181 vertical CO and NOx profiles, each averaged over
1 h, are available.
In mid-May 2001, sunrise was at about 05:45 CEST
and sunset took place at 21:00 CEST in the area. Mixing
started not later than 09 CEST and in most cases ended
after 17 CEST. To ensure development of a well-mixed
layer up to the height of the towers at least, as verified by
the backscatter signal of the SODAR, only measurements within this interval were taken to calculate source
intensities of CO and NOx. As a result of this criterion,
the number of 1 h profiles was reduced to 126.
Examples of potential temperature, wind speed, and
humidity profiles as well as the corresponding CO and
NOx profiles on both sides of the motorway are given in
Fig. 9. The profiles were recorded during SOP 4 on 14
May, a situation with southerly wind turning to south-
west during the day. Hence, the north tower was the lee
tower. One-hour mean profiles taken between 08 and 11
CEST are presented. Prandtl layer wind profiles were
found. Wind speed calmed down from 3.5 m s1 to
about 2.0 m s1 within the selected time. The temperature increased by about 3 1C and the stability in the
lower 18 m changed from stable at 08 CEST to unstable
at 11 CEST due to mixing starting at 08 CEST. The
humidity decreased with height. The number of vehicles
passing the measurement line between 07 and 08 CEST
increased from 2800 to 5500 per hour. The windward
profiles in Fig. 9 are constant with height, while the lee
profiles of both species are characterized by increased
concentrations at lower levels. The plume height is
between 15 and 30 m and the highest differences between
windward and lee side, 160 ppb for CO and 20 ppb for
NOx, respectively, are measured at 08 CEST when the
traffic reached its maximum and stratification was still
stable in the layer up to 18 m. The subsequent profiles
show a less-developed plume due to enhanced mixing
and reduced traffic density. It is important that the
individual signatures of the corresponding CO and NOx
profiles on the lee side are very similar. This indicates
that the measurement principle and its technical
implementation worked well.
The vertical profile of particle size distribution is very
similar to the concentration profiles of the exhaust gases.
ARTICLE IN PRESS
U. Corsmeier et al. / Atmospheric Environment ] (]]]]) ]]]–]]]
12
60
height in m agl
50
40
30
20
10
0
0
2
4
v in m s-1
292
294
7
Θ in K
8
9
q in g kg-1
60
CO 8:00
CO 9:00
200 300 400
200 300 400
CO 10:00
CO 11:00
200 300 400
200 300 400
height in m agl
50
40
30
20
10
0
ppb
60
NOX 8:00
NOX 9:00
NOX 10:00
NOX 11:00
height in m agl
50
40
30
20
10
0
0
20
40
0
20
8
40
9
0
ppb
10
20
40
0
20
40
11 CEST
Fig. 9. One hourly mean vertical profiles of wind speed WS, potential temperature Y; specific humidity q (upper diagrams), CO
(middle diagrams), and NOx (lower diagrams) measured at both towers on 14 May 2001 between 08 and 11 CEST. Mean wind
direction was about 1801. In the middle and lower diagrams the windward profiles (south tower, thin line) and lee profiles (north tower,
bold line) are given.
The particle plume height often varies between 10 and
30 m. The size distribution in the plume is characterized
by a double-peak structure: There are up to 70,000 very
small particles per cm3 (o 0.1 mm) and very few big
particles (41 mm). The small particles are supposed to
be primary soot emissions from the vehicles and
condensed sulfur particles. The greater ones are dust
particles dispersed by the cars, abrasion from tyres, and
coalesced soot particles (Imhof et al., 2005; Rosenbohm
et al., 2005).
ARTICLE IN PRESS
U. Corsmeier et al. / Atmospheric Environment ] (]]]]) ]]]–]]]
5. Summarizing remarks
It was shown that in cases of wind directions
perpendicular to the motorway, significant differences
in exhaust gas concentrations and particle concentrations can be measured between the windward side and
the lee of the motorway. In case of an appropriate traffic
census and a stringent quality control for the instruments, the method for determining real-world vehicle
emissions by calculating concentration differences works
quite well, as will be shown in the subsequent papers of
this issue, if essential prerequisites are fulfilled. These are
wind perpendicular to the motorway;
flat motorway and flat surrounding terrain, no flow
obstacles;
high and constant traffic density on the motorway;
no secondary emission sources nearby;
field measurements of sufficient time length;
highly developed emission calculation model, including details of the traffic census.
Gaseous and PM emissions measured by different
techniques as well as the calculated source intensities will
be reported in detail in the following papers. The
measured emissions and emissions calculated by a model
will then be compared in the final paper. The major
insights of BAB II, which will be explained in the
individual papers, are as follows:
In
comparison to tunnel studies, BAB II is much
more elaborate. The circumstances under which the
emissions are calculated are more realistic than in a
tunnel. On the other hand, the uncertainties of the
measurements may be greater in case of an open
motorway, if the prerequisites for the method are not
exactly fulfilled.
A pronounced double-peak structure with a lot of
very small particles emitted by the vehicles was
detected in the particle size distributions measured
close to the motorway.
Atmospheric turbulence induced by the vehicles is an
important factor when determining the exhaust gas
and particle distribution near the motorway by
numerical models (Bäumer et al., 2005).
The range of influence of motorway or vehicleinduced turbulence is restricted to the area near the
ground up to a maximum distance of 50 m in the lee
of the motorway. The turbulent kinetic energy,
correlating mainly with HDV density, measured at
a distance of 2.5 m in the lee is about 70% higher
than on the windward side and therefore should not
be neglected in turbulence parameterizations schemes
of diffusion models (Kalthoff et al., 2005).
13
Evaluated numerical emission models represent sensitive tools for sophisticated emission calculations and
forecasts. Among others, the efficiency of future
emission reduction strategies can be determined, the
consequences of new traffic routes for the residents can
be calculated, and ozone predictions can be made.
Acknowledgments
The authors gratefully acknowledge the commitment
and assistance of G. Emmert and D. Wacker, land
owners of the fields where the BAB II equipment was
installed. Thanks also go to the authorities of the City of
Heidelberg for their cooperation in granting the permits
to build up the measuring lines on public and private
ground. The BAB II project was partly funded by the
Umweltbundesamt (UBA), Berlin, Germany, under
contract number 299-42-250.
BAB II was coordinated and mainly funded by the
Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung (IMK). External participants
were the universities of Copenhagen, Stuttgart, Wuppertal, Heidelberg, Frankfurt, and Karlsruhe, the Paul
Scherrer Institut (PSI), (Switzerland), the Umweltbundesamt (UBA), Berlin and industry (BASF AG and
Ford Forschungszentrum).
References
Bäumer, D., Vogel, B., Fiedler, F., 2005. A new parameterisation of motorway induced turbulence and its application in
a numerical model. Atmospheric Environment, this issue.
Chock, D.P., 1980. General motors sulfate dispersion experiment. An analysis of the wind field near a road. BoundaryLayer Meteorology 18, 431–451.
Corsmeier, U., Kühlwein, J., Vogel, B., Kohler, M., Vogel, H.,
2005. Comparison of measured and model calculated real
world traffic emissions. Atmospheric Environment, this
issue.
De Vlieger, I., 1997. On-board emission and fuel consumption
measurement campaign on petrol driven passenger cars.
Atmospheric Environment 31, 3753–3761.
Eskridge, R.E., Rao, S.T., 1983. Measurement and prediction
of traffic induced turbulence and velocity fields near
roadways. Journal of Applied Meteorology 22, 1431–1443.
Eskridge, R.E., Thomson, R.S., 1982. Experimental and
theoretical study of the wake of a block-shaped vehicle in
a shear-free boundary flow. Atmospheric Environment 16,
2821–2836.
Friedeburg, Ch.V., Pundt, I., Mettendorf, K.-U., Wagner, Th.,
Platt, U., 2005. Multi-axis (MAX) DOAS measurements of
NO2 during the BAB II motorway emission campaign
Atmospheric Environment, forthcoming.
Gomes, J.A.G., Kurtenbach, R., Lörzer, J.C., Wiesen, P., 2005.
Emission factors of nonmethane hydrocarbons and nitrogen
oxides measured in a German road traffic tunnel—the effect
ARTICLE IN PRESS
14
U. Corsmeier et al. / Atmospheric Environment ] (]]]]) ]]]–]]]
of catalyst-equipped vehicles. Journal of Environmental
Monitoring, in preparation.
Heeb, N.V., Forss, A.M., Bach, Ch., Mattrel, P., 2000.
Velocity-dependent emission factors of benzene, toluene
and C2-benzenes of a passenger car equipped with and
without a regulated 3-way catalyst. Atmospheric Environment 34, 1123–1137.
Imhof, D. Weingartner, E. Baltensperger, U. Vogt, R.
Dreiseidler, A. Rosenbohm, E. Scheer, V. Kurtenbach, R.
Corsmeier, U. Kohler, M. 2004. Vertical distribution of
aerosol particles and NOx close to a motorway. Atmospheric Environment, this issue.
John, C., 1999. Emissionen von Luftverunreinigungen aus dem
StraXenverkehr in hoher räumlicher und zeitlicher Auflösung. Untersuchung von Emissionsszenarien am Beispiel
Baden-Württembergs. Institut für Energiewirtschaft und
Rationelle Energieanwendung (IER), Universität Stuttgart,
Forschungsberichte Bd. 58.
Kalthoff, N., Corsmeier, U., Fiedler, F., 1991. Modification of
turbulent fluxes and temperature fields in an atmospheric
surface layer over two adjacent agricultural areas: a case
study. Annals of Geophysics 9, 521–533.
Kalthoff, N., Corsmeier, U., Schmidt, K., Kottmeier, Ch.,
Fiedler, F., Habram, M., Slemr, F., 2002. Emissions of the
city of Augsburg determined using the mass balance
method. Atmospheric Environment 36 (Suppl. 1), S19–S31.
Kalthoff, N. Bäumer, D. Corsmeier, U. Kohler, M. Vogel, B.
Fiedler, F. 2005. Vehicle-induced turbulence near a motorway. Atmospheric Environment, this issue.
Kanter, H.-J., Mohnen, V.A., Volz-Thomas, A., Junkermann,
W., Glaser, K., Weitkamp, C., Slemr, F., 2002. Quality
assurance in TFS for inorganic compounds. Journal of
Atmospheric Chemistry 42, 235–253.
Kohler, M., Corsmeier, U., Kalthoff, N., Vogel, B., Baumbach,
G., Vogt, U., Vogt, R., Scherer, V., Rosenbohm, E.,
Kurtenbach, R., Petrea, M., Bär, M., Flocken, R., Pundt,
I., Jaeschke, W., Fuchs, J., 2005. Estimation of real world
traffic emissions downstream a motorway. Atmospheric
Environment, this issue.
Kühlwein, J., Friedrich, R., 2005. Traffic measurements and
high performance modeling of motorway. emission rates
Atmospheric Environment, this issue.
Kühlwein, J., Friedrich, R., Kalthoff, N., Corsmeier, U., Slemr,
F., Habram, M., Möllmann-Coers, M., 2002. Comparison
of modelled and measured total CO and NOx emission
rates. Atmospheric Environment 36 (Suppl. 1), S53–S60.
Lazaridis, M., Semb, A., Pacyna, J., Hov, Ø., Schaug, J.,
Larssen, S., Tarrason, L., Tsyro, S., Simpson, D., Olendrzynski, K., Andersson-Sköld, Y., 2000. Status report with
respect to measurements, modelling and emissions of
particulate matter in EMEP: an integrated approach.
EMEP Report 5/2000 (pdf, 1.6MB).
Leisen, P., Mülle, W.-R., Heich, H.-J., Hasselbach, W., Müller,
J., Waldeyer, H., 1992. Entwicklung der Abgasbelastung an
Autobahnen. Umweltbundesamt, Berlin, (UFOPLAN-Nr.
104 02 585).
Memmesheimer, M., Lehnhardt, A.L., Oberreuter, A., Jakobs,
H.J., Hass, H., Piekorz, G., Bock, H.J., Beck, J., Friedrich,
R., 1996. Impact of changes in VOC- and NOx-emissions on
photo-oxidant concentration over Europe as calculated with
the EURAD model. In: Borell, P.A. (Ed.), Proceedings of
the EUROTAC Symposium ’96. Computational Mechanics
Publications, Southampton, pp. 589–594.
Obermeier, A., Friedrich, R., John, C., Seier, J., Vogel, H.,
Fiedler, F., Vogel, B., 1995. Photosmog—Möglichkeiten
und Strategien zur Verminderung des bodennahen Ozons.
Ecomed Verlagsgesellschaft, Landsberg.
Olivier, J.G.J., Berdowski, J.J.M., 2001. Global emissions
sources and sinks. In: Berdowski, J., Guicherit, R., Heij,
B.J. (Eds.), The Climate System. A.A. Balkema Publishers/
Swets & Zeitlinger Publishers, Lisse, The Netherlands, pp.
33–78.
Petrea, M., Kurtenbach, R., Wiesen, P., Vogt, U., Baumbach,
G., Fuchs, J., Jaeschke, W., 2005. NMVOC measurements
of motorway. emissions during the BAB II campaign
Atmospheric Environment, this issue.
Pierson, W.R., Gertler, A.W., Robinson, N.F., Sagebiel, J.C.,
Zielinska, B., Bishop, G.A., Stedman, D.H., Zweidinger,
R.B., Ray, W.D., 1996. Real-world automotive emissions—
summary of studies in the Fort McHenry and Tuscarora
mountain tunnels. Atmospheric Environment 30,
2233–2256.
Pundt, I., Mettendorf, K.-U., Laepple, T., Knab, V., Xie, P.,
Lösch, J., v. Friedeburg, Ch., Platt, U., Wagner, T., 2005.
Measurements of trace gas distributions by long-path
DOAS tomography: 2D mapping of NO2 during the
motorway campaign BAB II. Atmospheric Environment,
forthcoming.
Rao, K.S., Gunter, R.L., White, J.R., Hosker, R.P., 2002.
Turbulence and dispersion modeling near highways. Atmospheric Environment 36, 4337–4346.
Rosenbohm, E., Vogt, R., Scheer, V., Nielsen, O.J., Dreiseidler,
A., Baumbach, G., Imhof, D., Baltensperger, U., Fuchs, J.,
Jaeschke, W., 2005. Particulate matter measured at a
motorway during the BAB II campaign near Heidelberg
Atmospheric Environment, this issue.
Schmid, H., Pucher, E., Ellinger, R., Biebl, P., Puxbaum, H.,
2001. Decadal reductions of traffic emissions on a transit
route in Austria—results of the Tauerntunnel experiment
1997. Atmospheric Environment 35, 3585–3593.
Simpson, D., 1992. Long-period modelling of photochemical oxidants in Europe, model calculations for
July
1985.
Atmospheric
Environment
26
(A),
1609–1634.
Slemr, F., Baumbach, G., Blank, P., Corsmeier, U., Fiedler, F.,
Friedrich, R., Habram, M., Kalthoff, N., Klemp, D.,
Kühlwein, J., Mannschreck, K., Möllmann-Coers, M.,
Nester, K., Panitz, H.J., Rabl, P., Slemr, J., Vogt, U.,
Wickert, B., 2002. Evaluation of modeled spatially and
temporarily highly resolved emission inventories of photosmog precursors for the city of Augsburg: the experiment
EVA and its major results. Journal of Atmospheric
Chemistry 42, 207–233.
Staehelin, J., Schlapfer, K., Burgin, T., Steinemann, U.,
Schneider, S., Brunner, D., Bäumle, M., Meier, M., Zahner,
C., Keiser, S., Stahel, W., Keller, C., 1995. Emission factors
from road traffic from a tunnel study (Gubristtunnel,
Switzerland). Part I: concept and first results. Science of
the Total Environment 169, 141–147.
Umweltbundesamt (UBA), 1995. Handbuch für Emissionsfaktoren des StraXenverkehrs—Version 1.1 (published on
CD-ROM). Umweltbundesamt, Berlin.
ARTICLE IN PRESS
U. Corsmeier et al. / Atmospheric Environment ] (]]]]) ]]]–]]]
Umweltbundesamt (UBA), 1997. Daten zur Umwelt—Der
Zustand der Umwelt in Deutschland—Ausgabe 1997.
Umweltbundesamt, Berlin.
Vogel, B., Fiedler, F., Vogel, H., 1995. The influence of biogenic
VOC emissions in the state of Baden-Württemberg on the
ozone concentration during episodes of high air temperatures.
Journal of Geophysical Research 100, 22907–22928.
Vogel, B., Corsmeier, U., Vogel, H., Fiedler, F., Kühlwein, J.,
Friedrich, R., Obermeier, A., Weppner, J., Kalthoff, N.,
Bäumer, D., Bitzer, A., Jay, K., 2000. Comparison of
measured and calculated motorway emission data. Atmospheric Environment 34, 2437–2450.
Vogt, U., Dreiseidler, A., Baumbach, G., Kurtenbach, R.,
Petrea, M., Kohler, M., Corsmeier, U., 2005. Standardised
quality assurance scheme applied to air pollutant measure-
15
ments of the BAB II field experiment. Atmospheric
Environment, this issue.
Weingartner, E., Keller, C., Pfahel, W.A., Burtscher, H.,
Baltensperger, U., 1997. Aerosol emissions in a road tunnel.
Atmospheric Environment 31, 451–462.
Wenzel, A., 1998. Wissenschaftliche Berichte des Instituts für
Meteorologie und Klimaforschung der Universität Karlsruhe Nr 21, 74–95.
Wickert, B., Friedrich, R., Merten, D., 1998. Luftschadstoffemissionen in den neuen Bundesländern. GefahrstoffeReinhaltung der Luft 58, 51–55.
Zhang, Y., Stedman, D.H., Bishop, G.A., Guenther, P.L.,
Beaton, S.P., 1995. Worldwide on-road vehicle exhaust
emissions study by remote sensing. Environmental Science
and Technology 29, 2286–2294.