DECEMBER 2023
TECHNICAL NOTE
Evaluation of real-world vehicle emissions
in Abu Dhabi
Authors: Rohit Nepali, Yoann Bernard, and Kaylin Lee
INTRODUCTION
In 2021, the Emirate of Abu Dhabi had average air concentrations
of fine particles (PM
2.5
) and nitrogen dioxide (NO
2
) that were
around eight times higher and over three times higher, respectively,
than the latest World Health Organization (WHO) Air Quality
Guidelines.
1
Vehicle emissions from the road transport sector
are a major contributor to urban air pollution and resulting health
problems in many regions, including Abu Dhabi. According to the
2018 air emissions inventory conducted by the Environmental
Agency of Abu Dhabi (EAD), road transport was the source of 34%
of nitrogen oxides (NO
X
) emissions, 17% of PM
2.5
emissions, and
74% of carbon monoxide (CO) emissions in 2015.
2
Recognizing the significant contribution of road transport to
air pollution, the United Arab Emirates (UAE) has introduced a
range of federal policies to reduce emissions from the sector.
Euro 4 was introduced as a minimum emission standard
requirement for new cars, trucks, and buses sold from 2018
onward.
3
Additionally, in 2021, the government introduced a
new fuel standard to ensure that petrol fuel sold within the
country has no more than 10 ppm sulfur content, and this
1 Environmental Agency of Abu Dhabi, “Air Quality Annual Summary Report Abu
Dhabi 2021,” (2021), https://www.ead.gov.ae/-/media/Project/EAD/EAD/
Documents/Resources/AIR-QUALITY-ANNUAL-2021-ENG.pdf, p. 7 and p. 9. The
average annual concentration of PM
2.5
in Abu Dhabi was of 38.5 μg /m
3
against the
5 μg /m
3
WHO guideline. The average annual concentration of NO
2
in Abu Dhabi
was of 33 μg /m
3
against the 10 μg /m
3
WHO guideline.
2 NO
X
here includes nitric oxide (NO) and nitrogen dioxide (NO
2
). NO reacts with
oxygen or ozone in the air to form NO
2
; Environmental Agency of Abu Dhabi,
“Abu Dhabi Air Emissions Inventory 2018,” (2018), https://www.ead.gov.ae/-/
media/Project/EAD/EAD/Documents/Resources/Abu-Dhabi-Air-Emission-
Inventory-2018.pdf, p. 20.
3 Neha Bhatia, “Higher Emission Standards Reshaping UAE Vehicle Fleets,”
Construction Week Online, May 4, 2018, https://www.constructionweekonline.
com/news/article-49209-higher-emission-standards-reshaping-uae-vehicle-fleets.
complemented the existing low-sulfur standard for diesel fuel.
4
The availability of low-sulfur fuels has reduced the pollutant
emissions from the existing fleet and marked a crucial step
necessary to introduce the most advanced emission control
technologies, such as Euro 6.
5
In early 2023, the EAD partnered with emissions remote
sensing system provider Hager Environmental and Atmospheric
Technologies (HEAT), 4 Earth Intelligence (4EI), and the
International Council on Clean Transportation (ICCT) under The
Real Urban Emissions (TRUE) Initiative to conduct an emissions
testing campaign in Abu Dhabi. Emission data collected with
remote sensing technology provide insight into the real-world
performance of a city’s fleet because vehicles are measured in
real driving conditions.
This technical note assesses real-world NO
X
and particulate
matter (PM) emissions from light-duty and heavy-duty vehicles,
including taxis and city buses, operating in Abu Dhabi.
6
It also
compares the emission levels of these vehicles with similar
data collected in Europe. The note concludes with policy
recommendations to curb vehicle emissions in Abu Dhabi.
4 Anas Abdoun,“The Middle East Continues to Anticipate Implementation of
Low-Sulfur Fuels through 2025 | Stratas Advisors,”Stratas Advisors,March 30,
2023,https://www.stratasadvisors.com/insights/the-middle-east-continues-
to-anticipate-implementation-of-low-sulfur-fuels-through-2025/2023-03-
30t151600-0400;“Cleaner Fuels,” Government of the UAE,accessed October
24, 2023, https://u.ae/en/information-and-services/environment-and-energy/
the-green-economy-initiative/eorts-to-achieve-green-economy-/cleaner-fuels.
5 Katherine Blumberg, Michael Walsh, and Charlotte Pera, “Low-Sulfur Gasoline
and Diesel: The Key to Lower Vehicle Emissions,” (Washington, D.C.: International
Council on Clean Transportation, 2003), https://theicct.org/publication/low-
sulfur-gasoline-and-diesel-the-key-to-lower-vehicle-emissions/.
6 PM emissions include both PM
2.5
and PM
10
emissions. PM emissions from the
HEAT remote sensing device are derived using a light absorption technique. The
absolute levels might not reflect the mass that other laboratory techniques may
produce and are here used to reveal relative trends.
Acknowledgments: The authors are grateful for the significant contributions from project Lead Hussein I. Hamed, and reviewers Meera
M. Harara, Rashed M. Ekaabi, Hazem H. Qawasmeh and Ruqaya M. Mohamed of the Environmental Agency of Abu Dhabi, Yolla Hager
from Hager Environmental and Atmospheric Technologies, and Francisco Posada and Ana Beatriz Rebouças from the International
Council on Clean Transportation.
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EVALUATION OF REAL-WORLD VEHICLE EMISSIONS IN ABU DHABI
|
DECEMBER 2023
DATA COLLECTION AND PROCESSING
The emissions testing campaign was conducted from January 24
to February 6, 2023 in six sites in Abu Dhabi emirate: five in the
city of Abu Dhabi and one in the city of Al Ain.
7
Figure 1 shows
one of the measurement sites and demonstrates how HEAT’s
Emission Detecting and Reporting (EDAR) remote sensing device
measured the exhaust emissions from vehicles in Abu Dhabi.
HEAT’s technology uses laser sources and detectors that are
placed above a roadway and exhaust emissions are measured
via spectroscopy as vehicles pass by the measurement location.
Vehicle speed and acceleration are measured at the same time,
and a camera captures an image of the vehicle’s number plate to
obtain its (non-personal) information.
8
During the 15 days of testing, 108,957 measurements with valid
emissions and license plate readings were collected.
9
After data
processing and validation following methods described in prior
TRUE Initiative publications, 82,797 usable measurements were
7 Emirates News Agency, “Environment Agency - Abu Dhabi to remotely measure
vehicle emissions in Abu Dhabi,” February 2, 2023, https://wam.ae/en/
details/1395303124586.
8 The vehicle number plate measured during the emissions testing campaign
was shared by HEAT with the Abu Dhabi police to get access to vehicles
characteristics such as type, fuel, engine power, curb weight, make, model, model
year, and date of registration. No personal information was shared.
9 HEAT, internal report on EAD’s remote sensing campaign (October 30, 2023),
shared with the authors.
retrieved.
10
Vehicle specification data from the Abu Dhabi police
were used to distinguish vehicles’ essential attributes such as
their type (e.g., bus or passenger car), fuel, and model year.
This technical note focuses on the most common vehicle types in
the dataset: light-duty vehicles, taxis, and buses. Others, such as
two-wheelers and trucks, were underrepresented in the dataset
and were therefore not included in the analysis. Real-world
emissions from Abu Dhabi vehicles are compared with average
real-world emissions data collected in various European cities for
similar vehicles running on the same fuel.
11
EMISSIONS RESULTS
LIGHT-DUTY VEHICLES (LDVs)
The LDV data consisted of passenger cars and light commercial
vehicles measured in Abu Dhabi emirate. Figure 2 illustrates
the average mass of NO
X
emitted per kilogram of fuel burned
by diesel and petrol vehicles by model year, and the timeline in
which dierent emission standards were introduced in the UAE
and Europe. Recall that the UAE introduced a minimum emission
10 Duplicate vehicle specifications associated with unique plates in police data were
also removed after the police confirmed that vehicles of dierent types (e.g.,
motorcycles and trailers) can use the same plate number. Vehicles registered in
the police database after the campaign took place were also discarded. On data
processing and validation methods, see Yoann Bernard et al., “Determination of
Real-World Emissions from Passenger Vehicles Using Remote Sensing Data,”
(Washington, D.C.: International Council on Clean Transportation, 2018),
https://theicct.org/publication/determination-of-real-world-emissions-from-
passenger-vehicles-using-remote-sensing-data/.
11 The TRUE European dataset used for comparison includes Belgium, Czech Republic,
France, Italy, Poland, Spain, Sweden, Switzerland, and the United Kingdom. A direct
comparison of the Abu Dhabi results with previous TRUE European studies could
be complicated by a number of factors, such as dierences in instrumentation, site
conditions, data quality, and date of measurements.
Figure 1. HEAT EDAR remote sensing device measuring emissions from passing vehicles in Abu Dhabi. Source: Oriol Teixidó, former project lead at EAD.
3
EVALUATION OF REAL-WORLD VEHICLE EMISSIONS IN ABU DHABI
|
DECEMBER 2023
standard requirement of Euro 4 for new cars in 2018. The notable
decrease in the average fuel-specific NO
X
emissions for both
diesel and petrol vehicles of the 2018 model year seen in Figure 2
can be attributed to the adoption of the Euro 4 emission standard.
Despite the improvement in emission performance that Euro 4
vehicles demonstrated compared with vehicles of earlier model
years, diesel Euro 4 vehicles in Abu Dhabi still showed high
real-world NO
X
emissions. Such levels are in line with extensive
evidence from Europe showing that diesel Euro 4 vehicles emit
NO
X
at levels multiple times above the regulatory limit in real
driving conditions.
12
In addition, compared with diesel vehicles of the most recent
(post-2019) model years in Europe, diesel vehicles’ average NO
X
emissions in Abu Dhabi were 10 to 15 times higher. In Europe,
NO
X
emissions from diesel vehicles have steadily decreased over
the last decade, mainly due to the development of the Euro 6
regulation, which was introduced in late 2014.
13
Starting in late
2017, the Euro 6 regulation was further supplemented with on-
12 International Council on Clean Transportation, “New ICCT Study Shows Real-
World Exhaust Emissions From Modern Diesel Cars Seven Times Higher Than EU,
US Regulatory Limits,” October 11, 2014, https://theicct.org/press-release-new-
icct-study-shows-real-world-exhaust-emissions-from-modern-diesel-cars-seven-
times-higher-than-eu-us-regulatory-limits/.
13 The Euro 6 emission standard drove the use of NO
X
aftertreatment technologies
for diesel light-duty vehicles.
road type-approval testing requirements; such testing was fully
phased in with the Euro 6d standard in 2020, and it led to further
NO
X
reductions in real-world driving conditions.
Euro 4 petrol vehicles in Abu Dhabi, however, showed real-world
NO
X
emissions 44% lower than European vehicles certified to
the same standard; their emissions were more comparable with
those from European petrol vehicles certified to Euro 5. Emission
measurements from European vehicles used for comparison likely
show higher levels of NO
X
emissions because of deterioration
after more than 10 years of use.
14
This suggests that Euro 4
petrol vehicles in Abu Dhabi may also be prone to emission
deterioration. Additional measures would be necessary to help
ensure that new petrol cars introduced in Abu Dhabi are less
vulnerable to emission degradation (e.g., by mandating the Euro 6
standard for new vehicles).
The data further demonstrate that the introduction of Euro 4 led
to a substantial decrease in average PM emissions from diesel
vehicles.
15
As shown in Figure 3, the introduction of Euro 4 in
14 Jack Davison et al., “Gasoline and Diesel Passenger Car Emissions Deterioration
Using On-Road Emission Measurements and Measured Mileage,” Atmospheric
Environment: X, no. 14 (April 2022): 100162, https://doi.org/10.1016/j.
aeaoa.2022.100162.
15 PM emissions from petrol vehicles were below the detectable range of the remote
sensing units and hence were excluded from the analysis.
Diesel Petrol
0
10
20
30
40
50
Model year
Mean fuel−specific NO
X
emissions (g/kg)
Remote sensing
data source
Abu Dhabi
TRUE Europe
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
Euro 4
Euro 4
Euro 3
Euro 3
Euro 2
Euro 2
Euro 4
Euro 4
Euro 3
Euro 3
Euro 5
Euro 6
Euro 5
Euro 6
Euro 6d
Euro 6d
Figure 2. Average fuel-specific NO
x
emissions of light-duty vehicles by fuel type and model year in Abu Dhabi and Europe. Whiskers indicate the 95%
confidence interval of the mean. Blue and red labels represent the introduction of new emission standards in the European Union and Abu Dhabi, respectively.
Only results with at least 30 measurements are shown; measurements do not include taxis.
4
EVALUATION OF REAL-WORLD VEHICLE EMISSIONS IN ABU DHABI
|
DECEMBER 2023
2018 brought down PM emissions from diesel LDVs by between
61% and 82% relative to Euro 3 LDVs of 2011–2017 model years.
The resulting emission levels were in line with average PM
emissions of Euro 4 diesel vehicles measured in Europe. Those
levels are, however, still two to six times higher than those from
Euro 5 and eight to 10 times higher than those from Euro 6 LDVs
in Europe. Europe’s large improvement in PM performance is
attributable to diesel particular filters, which became compulsory
for all diesel vehicles to meet the Euro 5 limit from 2009 onward.
The comparison with the European fleet indicates that while
introducing the Euro 5 standard in Abu Dhabi would be expected
to reduce PM emissions from new vehicles, it would fall short
of curbing real-world NO
X
emissions. Leapfrogging to the Euro
6 standard for new LDVs would be expected to bring emission
benefits in terms of both PM and NO
X
.
EMISSIONS FROM PRIVATE LDVs, PUBLIC LDVs,
AND TAXIS
LDVs were further broken down into private, public, and taxis
based on vehicle specifications. In Abu Dhabi, private LDVs are
privately owned vehicles and public LDVs include vehicles used
for garbage pickup, food transport, and fuel transport. Figure 4
compares the fleet average NO
X
emissions from private, public,
and taxi LDVs.
For private and public LDVs, diesel vehicles were the oldest and
highest-emitting vehicles, emitting two to three times higher
average NO
X
emissions than their petrol counterparts. Hybrid
LDVs used for private and taxi purposes had the lowest average
age and the lowest average NO
X
emissions among all fuels, with
NO
X
emissions 90% lower than those from diesel LDVs.
Petrol-powered public LDVs showed 50% higher average NO
X
emissions than their petrol-powered private LDV counterparts,
despite similar average age. Petrol taxis, by contrast, showed
average NO
X
emissions similar to those of petrol-powered private
vehicles, despite being significantly younger. The emission gaps
seen in petrol vehicles across dierent ownership types may be
attributable to dierences in mileage, as public LDVs and taxis
are likely driven more per year than private LDVs.
16
Consistent
with findings of past studies, higher NO
X
emissions may reflect
a deterioration of vehicle emissions control systems in higher-
mileage vehicles.
17
16 Environmental Agency of Abu Dhabi, “Abu Dhabi Air Emissions Inventory 2018,”
p. 90.
17 Jens Borken-Kleefeld and Yuche Chen, “New Emission Deterioration Rates for
Gasoline Cars – Results from Long-Term Measurements,” Atmospheric Environment
vol. 101 (January 2015): 58–64, https://doi.org/10.1016/j. atmosenv.2014.11.013;
Yoann Bernard et al., “TRUE U.S. Database Case Study: Emissions Deterioration
of U.S. Gasoline Light-Duty Vehicles and Trucks,” (Washington, D.C.: International
Council on Clean Transportation, 2020), https://theicct.org/sites/default/files/
publications/US-TRUE-emissions-deterioration-oct2020.pdf; Kaylin Lee et al.,
“Evaluation of Real-World Vehicle Emissions in Warsaw,” (Washington, D.C.:
International Council on Clean Transportation, 2022), https://www.trueinitiative.
org/data/publications/evaluation-of-real-world-vehicle-emissions-in-warsaw.
Euro 3
Euro 4
Euro 5
Euro 6
Euro 6d
Diesel
0.0
0.5
1.5
1.0
2.0
2.5
4.0
3.5
3.0
5.0
4.5
Model year
Mean fuel−specific PM emissions (g/kg)
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
Remote sensing
data source
Abu Dhabi
TRUE Europe
Euro 2 Euro 3
Euro 4
Figure 3. Average fuel-specific PM emissions of light-duty vehicles for diesel fuel type by model year in Abu Dhabi and Europe. Whiskers indicate the 95%
confidence interval of the mean. Blue and red labels represent the introduction of new emission standards in the European Union and Abu Dhabi, respectively.
Only results with at least 30 measurements are shown; measurements do not include taxis.
5
EVALUATION OF REAL-WORLD VEHICLE EMISSIONS IN ABU DHABI
|
DECEMBER 2023
TAXI EMISSIONS
Taxis made up 12% of the valid measurements recorded during
the remote sensing campaign, and this highlights the significant
share of taxis in the city’s vehicle activities. Taxis in Abu Dhabi
cover extensive distances, with an average annual mileage of
around 150,000 km. Due to their higher mileage, the lifetime of
taxis is typically shorter than other LDVs, which have average
annual mileages of around 15,000 to 40,000 km per year.
18
Taxis running on compressed natural gas (CNG) represented 36%
of the taxi measurements. The government has promoted the
conversion of petrol vehicles to CNG since 2012.
19
By fuel type,
CNG taxis exhibited the highest level of NO
X
emissions, two and
a half times higher than petrol-powered taxis and 15 times higher
than hybrids (Figure 4). This aligns with the findings of a study
conducted in European cities which found that passenger cars
powered by natural gas had higher average NO
X
emissions than
those powered by petrol.
20
Given that most of these CNG vehicles
are likely converted from petrol vehicles, this raises concerns
about a potential lack of NO
X
emission verification at the time
of the CNG conversion for vehicles that showed elevated NO
X
emission levels. The dierence may also be partially explained
by the higher average age, and therefore likely higher mileage, of
18 Environmental Agency of Abu Dhabi, “Abu Dhabi Air Emissions Inventory 2018,”
p. 90.
19 Anwar Ahmad, “Capital Switching to CNG Gradually,” Khaleej Times, updated April
7, 2015, https://www.khaleejtimes.com/article/capital-switching-to-cng-gradually.
20 City Air Remote Emission Sensing (CARES), “Summary Report on Partner Cities’
Measurement Campaigns,” (April 2023), https://cares-project.eu/wp-content/
uploads/2023/06/CARES-814966-D3.4-Summary-report-on-partner-cities-
measurement-campaigns.pdf.
taxis running on natural gas, which are 1.5 and 2 years older than
average hybrid and petrol taxis, respectively.
Toyota Camrys constituted 94% of the taxis measured and were
therefore chosen for a more in-depth analysis. The methodology
from a previous ICCT study was employed to combine real-
world fuel economy estimates with fuel-specific NO
X
emission
values of Toyota Camry taxis to derive distance-specific
emissions (g/km) for dierent fuel types.
21
The method was
not applicable at the fleet level due to the lack of information on
real-world fuel economy.
An assessment of mean NO
X
emissions from taxis of dierent
model years and fuel types is presented in Figure 5. The results
show that petrol and natural gas taxis are largely responsible for
NO
X
emissions. A large share of petrol and CNG taxis are Euro 3
vehicles, or those of model years 2016–2017, and those vehicles
21 Bernard et al., “Determination of Real-World Emissions from Passenger Vehicles”;
Yoann Bernard, Jan Dorno, and David C. Carslaw, “Can Accurate Distance-
Specific Emissions of Nitrogen Oxide Emissions from Cars Be Determined
Using Remote Sensing without Measuring Exhaust Flowrate?,” Science of
The Total Environment vol. 816 (2022): 151500, https://doi.org/10.1016/j.
scitotenv.2021.151500. Average fuel-economy was estimated based on type-
approval information of the latest Euro 4 Toyota Camry models in Abu Dhabi
and estimates of the gap between real-world and laboratory performance were
based on studies from Europe on Euro 4 vehicles between 2005 and 2009. The
approach assumes conservatively low fuel consumption that leads to conservative
NO
X
emission estimates, although the gap seen in Europe grew when Euro 5 and
6 were introduced. On the gap between real-world and laboratory performance,
see Jan Dorno et al., “On the Way to ‘Real-World’ CO
2
Values: The European
Passenger Car Market in its First Year After Introducing the WLTP,” (Washington,
D.C.: International Council on Clean Transportation, 2020), https://theicct.org/
publication/on-the-way-to-real-world-co2-values-the-european-passenger-car-
market-in-its-first-year-after-introducing-the-wltp/. The following values for the
fuel economy of Toyota Camry vehicles were considered: petrol: 8.0 L/100 km;
hybrid: 4.6 L/100 km; and CNG, 5.5 kg/100 km. The lower fuel consumption
of hybrid vehicles allows us to factor in the share in electric mode driving when
converting the NO
X
-to-fuel ratio per kilometer driven.
8 yr
7 yr
7.8 yr
10.5 yr
6.6 yr
2.5 yr
4.5 yr
2.4 yr
3 yr
3k 1963854k 2k 1k 3k4k4k
0
10
20
30
Private
Diesel
Petrol
Natural gas
Hybrid
Fuel type
Public
Light-duty vehicle type
Taxi
Mean fuel−specific NO
X
emissions (g/kg)
Figure 4. Average fuel-specific NO
x
emissions of light-duty vehicles by plate and fuel type for dierent model years in Abu Dhabi. Whiskers indicate the 95%
confidence interval of the mean. The number below each bar shows the number of measurements; the number above each bar indicates the average age of
the vehicles assessed in each category. Only results with at least 30 measurements are shown.
6
EVALUATION OF REAL-WORLD VEHICLE EMISSIONS IN ABU DHABI
|
DECEMBER 2023
showed the highest NO
X
emissions among taxis. Also, petrol and
CNG taxis of model years 2018–2020 had real-world emissions
eight to 19 times higher than their hybrid counterparts and three
to 12 times higher than regulatory limits.
Newer Toyota Camry petrol taxis of 2021, 2022, and 2023
model years showed a notably improved emission performance
and exhibited average NO
X
emissions similar to their hybrid
counterparts. All hybrid taxis showed real-world mean NO
X
emissions in line with the regulatory limit.
The results further highlight that age and mileage could be key
influencing factors for elevated NO
X
emissions from non-hybrid
taxis. Many taxis in Abu Dhabi emirate have likely accrued
mileages beyond vehicle manufacturer emission durability
requirements (e.g., 100,000 km for Euro 4 vehicles) in their
first years of operation. Although Euro 4 brought a significant
improvement in the emission performance of petrol and CNG
taxis, vehicles of model years 2016–2020, which likely do not
meet durability requirements, all showed NO
X
emissions three to
15 times regulatory limits.
22
These high levels of NO
X
emissions
could also be attributable to unreported cases of petrol vehicles
converted to CNG. That petrol taxis of model years 2021–2023
complied with the emission limits lends weight to this. There are
22 There were fewer private Toyota Camry LDV cars running on petrol fuel than taxis.
Model year 2019 had the highest number of measurements across all other model
years and showed 10 times lower NO
x
emissions than 2019 Toyota Camry petrol taxis.
fewer economic incentives for hybrid taxi owners to convert to
CNG relative to petrol taxi owners, and that could explain why
older hybrid models seem relatively unaected.
Pre-2018 Toyota Camry taxis were responsible for 55% of total
NO
X
emissions from the taxi fleet, although they accounted for
around 17% of taxi measurements recorded during the Abu
Dhabi campaign.
23
Abu Dhabi has set a 5-year age limit for taxis,
but measurements from pre-2018 models indicated that around
17% of taxis exceeded that age. Abu Dhabi emirate’s Integrated
Transport Center (ITC), which oversees taxi licensing, indicated
that its agreement with franchise companies provides an option
to extend the use of taxis awaiting franchise renewal. These
results further highlight the emission benefits that would be
expected from stricter application of the age limit.
BUS EMISSIONS
Multiple bus service lines operate in Abu Dhabi. Public city
and intercity buses are operated mainly by ITC, while Emirates
Transport, a federal government-owned entity, runs school buses
throughout Abu Dhabi and surrounding emirates. Several private
bus operators also run coaches to serve commuters in the region.
23 The share of remote sensing measurements is considered a crude proxy of vehicle-
kilometers traveled by each group of vehicles, such as pre- and post-2018 models.
The share of emissions is then calculated within each group as the product of the
share of measurement by their estimated distance-specific emissions.
NO
X
limit
NO
X
limit
NO
X
limit
0.0
0.5
1.0
1.5
2.0
2.5
Model year
Mean distance−specific NO
X
emissions (g/km)
Toyota Camry
Petrol
Toyota Camry
Natural gas
Toyota Camry
Hybrid
135 367309 216 598 442 777 331
2016 20192017 2018 2020
289 999958951 734 593 7451K 377 183
2021 2022 2023 2016 20192017 2018 2020 2021 2022 2023 2016 20192017 2018 2020 2021 2022 2023
Emission standard
Euro 4
Euro 3
Figure 5. The estimated average distance-specific NO
x
emissions of Toyota Camry taxis running in Abu Dhabi by fuel type for dierent model years and
minimum emission standards. Whiskers indicate the 95% confidence interval of the mean. The number below each bar shows the number of measurements.
Only results with at least 100 measurements are shown. Dotted lines represent the type-approval limit for the respective emission standards.
7
EVALUATION OF REAL-WORLD VEHICLE EMISSIONS IN ABU DHABI
|
DECEMBER 2023
0
10
20
30
40
Model year
Mean fuel−specific NO
X
emissions (g/kg)
102 399149 319 59 244672 80 183 215 208 266264 101 144 393 969 925341 66 256 321 180 20065 27683882k 384517
2006 20092007 2008 2010 2014 20172015 2016 2018 2019 20222020 20212011 2012 2013
Remote sensing
data source
Abu Dhabi
TRUE Europe
Diesel
Euro IV
Euro IV
Euro VI-D
Euro VI
Euro VI
Mean fuel−specific
NO
X
emissions (g/kg)
Mercedes−Benz CitaroVolvo B11 R
2020 2021 2020 2021
Model year
5
4
3
2
1
0
Figure 6. Average fuel-specific NO
X
emissions of diesel buses by model year in Abu Dhabi. Whiskers indicate the 95% confidence interval of the mean. The
number below each bar shows the number of measurements. Blue and red labels in the main figure represent the introduction of new emission standards in
the European Union and Abu Dhabi, respectively. Only results with at least 50 measurements are shown. The right-hand figure shows the average fuel-
specific NO
x
emissions of new Euro VI buses operated by ITC in Abu Dhabi by model year.
Euro IV
Euro IV
Euro VI-D
Euro VI
0.0
2.0
1.5
1.0
0.5
2.5
3.0
3.5
4.0
Model year
Mean fuel−specific PM emissions (g/kg)
73 399149 331 57 244673 78 188 215 229 266264 107150 393 1k 925341 56 154 321 147 20065 25680992k 384517
2006 20092007 2008 2010 2014 20172015 2016 2018 2019 20222020 20212011 2012 2013
Abu Dhabi
TRUE Europe
Diesel
Euro VI
Mercedes−Benz CitaroVolvo B11 R
Mean fuel−specific PM
emissions (g/kg)
2020
1.0
0.8
0.6
0.4
0.2
1.0
2021 2020 2021
Model year
Below detection level
Remote sensing
data source
Figure 7. Average fuel-specific PM emissions of diesel buses by model year in Abu Dhabi. Whiskers indicate the 95% confidence interval of the mean. The
number below each bar shows the number of measurements. Blue and red labels in the main figure represent the introduction of new emission standards in
the European Union and Abu Dhabi, respectively. Only results with at least 50 measurements are shown. The right-hand figure shows the average fuel-
specific PM emissions of new Euro VI buses operated by ITC in Abu Dhabi by model year.
8
EVALUATION OF REAL-WORLD VEHICLE EMISSIONS IN ABU DHABI
|
DECEMBER 2023
Public and private buses were 29% and 71%, respectively, of
buses measured in the Abu Dhabi campaign.
Figure 6 and Figure 7 show that average NO
X
and PM emissions
from diesel buses of model years before 2019 are two to eight
times higher than those from buses of the same model year
operating in Europe. Most of these are Euro II and Euro III buses
without diesel NO
X
exhaust aftertreatment systems. In 2018,
with the introduction of Euro IV, average PM emissions from
diesel buses were reduced by 75%, whereas NO
X
emissions
were unchanged.
We also found that average NO
X
and PM emissions from buses
of model year 2020 fell by 75% compared with those of model
year 2019. The data revealed that 80% of buses of model year
2020 and 37% of buses of model year 2021 were certified to
Euro VI. ITC ordered 168 new Volvo B11 R intercity coaches and
99 new Mercedes-Benz Citaro city buses with Euro VI diesel
engines in 2019 and 2020, respectively.
24
These new buses came
into operation in 2020 and show significantly lower NO
X
and PM
emissions than Euro IV buses.
25
For buses of model years 2021 and
2022, both average NO
X
and PM emissions went up compared
to model year 2020, as buses bought during those years were
presumably certified to Euro IV or Euro V emission standards.
26
POLICY RECOMMENDATIONS
The data collected during the Abu Dhabi vehicle emissions testing
not only oered insight into the real-world emissions of the fleet
currently on the road but also helped to assess the eectiveness of
past and current vehicle policies in the emirate. The study findings
provide evidence to support the following new policy actions that
could help to reduce emissions from on-road vehicles.
ADOPTION OF EURO 6 STANDARDS FOR NEW LDVs
This study showed that the introduction of Euro 4 in 2018
significantly reduced NO
X
and PM emissions from LDVs in Abu
Dhabi, especially diesel-powered ones. Even so, these vehicles
emit 10 to 15 times higher NO
X
and PM emissions than average
vehicles of the same model year in Europe. There is a vast evidence
base from Europe indicating that the Euro 6 standard was able
to ensure improved NO
X
and PM emission performance from
diesel vehicles that Euro 5 did not deliver. For diesel vehicles in
the UAE, we recommend the implementation of the Euro 6 “d”
24 Volvo Buses, “Abu Dhabi Orders 168 Volvo Intercity Coaches,” July 11, 2019,
https://www.volvobuses.com/en/news/2019/jul/abu-dhabi-orders-168-volvo-
intercity-coaches.html; Mercedes-Benz, “99 Mercedes-Benz Citaro City Buses to
Operate in Abu Dhabi’s Public Transport Network,” April 17, 2020, https://www.
mercedes-benz-bus.com/en_CY/brand/news/2020/99-mercedes-benz-citaro-
city-buses-to-operate-inpublic-transport-network-in-abu-dhabi.html.
25 Emirates News Agency, “ITC Operates New Buses, Oers 244 Additional
Daily Trips during Peak Hours,” October 13, 2021, https://www.wam.ae/en/
details/1395302980250.
26 No evidence that other models could be type-approved to Euro VI was found, and
their NO
X
and PM emission performance suggests they would be Euro IV or at
best Euro V.
stage or higher, which would support significantly lower real-world
NO
X
emission levels. In addition, for petrol vehicles, the Euro 6
standard sets higher requirements for emission durability to limit
the deterioration seen from petrol Euro 4 and Euro 5 vehicles in
Europe. By setting the minimum standard for new LDVs as Euro
6, the UAE could achieve a large reduction in pollutant emissions
from new vehicles and set the stage for long-term reductions in
emissions from the future fleet. The cost for manufacturers to
meet the latest Euro 6 standard is expected to be below 1% and
4% of the retail price for petrol and diesel LDVs, respectively.
27
The
UAE government could further consider an import ban on used
or second-hand vehicles certified to below Euro 4 for petrol and
below Euro 6 for diesel vehicles and, to accelerate fleet renewal, a
scrappage program for the oldest vehicles.
PURCHASING BUSES CERTIFIED TO AT MINIMUM EURO
VI OR EQUIVALENT EMISSION STANDARDS
The Euro IV minimum requirement for new buses introduced in
2018 delivered a substantial reduction in PM emissions from Abu
Dhabi’s fleet, but relatively minor NO
X
emission benefits. A small
number of Euro VI buses that Abu Dhabi introduced following
procurement by ITC in 2019 and 2020 showed NO
X
emissions
94% lower and PM emissions 86% lower than other buses in
the emirate certified to the Euro IV minimum. We recommend
that the Abu Dhabi government continue to acquire buses with
minimum Euro VI standards, and preferably of the “D” stage or
higher, because remote sensing data collected in Europe shows
these buses generate around 66% lower NO
X
emissions in urban
conditions than Euro VI pre-D buses. Buses of model year 2017
and earlier, which are likely certified to Euro III and below and
are responsible for a disproportionate share of emissions in Abu
Dhabi, could also be replaced with Euro VI buses or, even better,
electric buses. A study from the ICCT estimated that the cost of
Euro VI for manufacturers would be under 1% of the retail price.
28
STRENGTHENING THE APPLICATION OF THE 5-YEAR
AGE LIMIT FOR TAXIS
This study found that taxis more than 5 years old accounted for a
disproportionate share of emissions: despite comprising around
17% of the taxi fleet in Abu Dhabi, they were responsible for at
least 55% of total NO
X
taxi emissions. Taxis older than 5 years,
driving under a derogation of their franchise awaiting renewal,
were estimated to emit up to 15 times their type-approval limit.
27 Francisco Posada Sanchez, Anup Bandivadekar, and John German, “Estimated
Cost of Emission Reduction Technologies for LDVs,” (Washington, D.C.:
International Council on Clean Transportation, 2012), https://theicct.org/
publication/estimated-cost-of-emission-reduction-technologies-for-ldvs/. Cost
estimate was updated in 2016 and therefore gives a ballpark estimate for 2023
prices. Current prices may be lower, as aftertreatment technology has improved
and decreased in cost. The cost for Euro 6d gasoline is expected to be around
100 USD more than for early phase of the Euro 6 due to the need for a gasoline
particulate filter.
28 Yihao Xie, Francisco Posada, and Arijit Sen, “Soot-Free Road Transport in South
Africa: A Cost-Benefit Analysis of Euro VI Heavy-Duty Vehicle Standards,”
(Washington, D.C.: International Council on Clean Transportation, 2022),
https://theicct.org/publication/africa-me-hvs-soot-south-africa-dec22/.
TRUE—The Real Urban Emissions Initiative FIA Foundation, 60 Trafalgar Square, London WC2N 5DS, United Kingdom
For more information contact: true@fiafoundation.org | @TRUE_Emissions | www.trueinitiative.org
TRUE PARTNERS
LEAD PROJECT PARTNER AND COMMISSIONER
CONSORTIUM PARTNERS
These findings reiterate the importance of an age limit and
potential mileage cap for the taxi fleet. Among other measures,
a stricter application of the rules limiting derogations combined
with stringent enforcement for taxis (e.g., by using automatic
number plate recognition cameras or remote sensing for vehicle
emission monitoring), could significantly reduce this fleet’s
emission impact. Abu Dhabi could further promote the use of
more fuel-ecient taxis, such as hybrid vehicles, which were
shown to provide fuel and greenhouse gas emissions savings and
which exhibited real-world NO
X
emissions consistently below the
limit across dierent model years.
ELECTRIFICATION OF THE VEHICLE FLEET
Electric vehicles emit zero tailpipe pollutant and greenhouse gas
emissions and fleet electrification is the fastest way to reduce
harmful emissions from motor vehicles. We recommend that
Abu Dhabi accelerate the electrification of its public transport,
government, and taxi fleet by setting zero-emission vehicle
targets.
29
At the federal level, policies such as a zero-emission
vehicle mandate or CO
2
standard for new vehicles would foster
the uptake of electric vehicles and help individual emirates align
with federal air quality and climate targets.
29 Based on the taxi fleet measured in this project, we estimate that a policy
targeting an eight-percentage-point increase in new purchases of zero-emission
taxies per year would lead to a fully electrified taxi fleet by 2035 and an increase
in vehicle activity of 7% each year.
For details on the TRUE remote sensing database,
contact Yoann Bernard, y[email protected].
For more information on TRUE, visit www.trueinitiative.org.