Transport & Air Quality

Today, more than half the world’s population live in urban areas and this number is expected to increase to more than two thirds by 2050 according to United Nations. Therefore, sustainable development challenges will primarily arise in these regions. Cities account for more than 80 % of global Gross Domestic Product (GDP), they consume two-thirds of total primary energy and produce over 70 % of global energy-related CO2 emissions according to the World Bank and the International Energy Agency.

As the world is urbanizing the need for a sustainable development pattern and a shift to more compact urban growth, connected infrastructure, and coordinated governance is essential as stated in the New Climate Economy Report. Most of the urban development around the world has taken place in an unsustainable manner exacerbating problems as air pollution and traffic congestion.


Air Quality

Air quality is measured in terms of the pollutants present that are known to be harmful to human health. The main four pollutants that may be easily modelled are: Nitrogen Dioxide, Ozone, PM10 and PM2.5 particulates. PM10 and PM2.5 are given different names due to the size of the particles, PM2.5 are less than 2.5 micrometers in diameter and can be breathed into the deepest part of the lung causing the most harm.

The current EU air quality standards are:

Pollutant Concentration Limit Averaging Period
PM2.5 25 µg/m3*** 1 year
PM10 50 µg/m3 24 hours
  40 µg/m3 1 year
Nitrogen Dioxide 200 µg/m3 1 hour
  40 µg/m3 1 year
Ozone 120 µg/m3 Maximum mean over 8 hour period

The PM2.5 values around the world are seen below from data collected by the world bank:

Screen Shot 2016-02-01 at 22.16.25



As indicated in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change the transport sector was responsible for approximately 23 % of total energy-related CO2 emissions (6.7 GtCO2) in 2010. Reducing global transport greenhouse gas (GHG) emissions will be challenging but some important efforts to promote mitigation actions in the transport sector and to change urban mobility are already taking place in cities around the world:

Sustainable Transport Adoption Curves














Source: Embarq, 2013


Sustainable Urban Mobility in London

Transport is an important contributor to London’s GHG emissions, for this reason the city aims to reduce CO2 emissions by 60 % in 2025 (from 1990 levels).

CO2 emissions in Greater London

CO2 emissions in Greater London.jpg











Source: London Atmospheric Emissions Inventory, 2010


In order to achieve this target and promote sustainable urban mobility the city government is introducing the following top ten measures:

1) Implementing an Ultra Low Emission Zone (ULEZ) in central London

2) Tightening the Low Emission Zone

3) Making traffic management and regulation smarter

4) Helping Londoners tackle air pollution and climate change

5) Driving the uptake of Low Emission Vehicles

6) Cleaning up electricity for London’s transport

7) Transforming London’s bus fleet

8) Delivering zero emissions taxi and private hire fleets

9) Transforming London’s public and commercial fleets

10) Developing Low Emission Neighbourhoods


Source: Transport Emissions Roadmap, 2014