Carbon Emissions and Air Pollution – Implications for Urban Mobility

Posted by on Oct 22, 2019 in Cardiff, News | No Comments

Carbon Emissions and Air Pollution – Implications for Urban Mobility

Debate 4th October 2019

Summary Report of Discussion and Key Learning Points



The expected publication of a White Paper on future transport plans for Cardiff by the City Council in Autumn 2019 follows a council Green Paper and consultation in 2018 and initial transport changes to resolve the worst air pollution hotspots in the city due to start immediately. Cardiff Civic Society (CCS) has been encouraged by the council to run this debate to provide guidance on best practice and trends to inform the White Paper. This debate is a joint event by CCS and Cardiff University School of Geography and Planning.

What follows is a brief outline of the proceedings and extraction of key learning points and conditions for successful application of schemes designed to maximise mobility around the city and make a substantial contribution to both CO2 emission reductions and air quality. High levels of CO2 and air pollutants are an inconvenient consequence of our creation of a car society over 50 years that have shaped our cities to accommodate cars rather than people.

The views expressed below are CCS views, not necessarily those of the university.


The agenda can be viewed here – Climate Change and air pollution




Dr. Porter’s Presentation can be viewed here – Tom Porter Moving Forwards Healthy Travel for all


This presentation underlined the diminishing use of buses (42% to 5%) and cycles (11% to1%), and corresponding increase of car usage (27% to 83%) over the last 50 years and our progressive shaping of communities to car use rather than people. It is no accident that obesity, road deaths of children and respiratory illnesses leading to premature death are increasing dramatically, and road design and traffic is causing social isolation. There are no safe levels of air pollution, current efforts are aimed at the limited objective of avoiding legal challenge due to exceeding maximum WHO levels. Cardiff is reported as having the worst air quality outside of London.

The rate of decline in CO2 emissions is not consistent with achieving net zero emissions by 2050 and needs something like a 10-fold acceleration. Transport is associated with some 25% of emissions and has had less improvement than the energy sector. This suggests that it is the transport sector that must shoulder much of the effort for the next phase of reduction.

The move towards electric vehicles (EV) is necessary but not a panacea, lifecycle CO2 emissions are only better than conventional cars if the grid is 100% renewable. The battery manufacturing process is a big CO2 emitter, and requires both longer battery life and effective battery recycling. In addition, we can expect no improvement in road casualties and little improvement in particle emissions as a result of EV.

The current actions in Cardiff including an increase in cycle use, Next bikes, NOX reduction zones, 20mph zones and planned adoption of a Metro style network will improve both CO2 and air quality but not at the rate needed to support the 2050 targets or widespread air quality consistent with a liveable city.

In response to questions, the need for Metro and restrictions to car access to the city were cited. Future development must be supported by public transport; behaviours are established at the start of new communities and s106 monies can be applied in support of sustainable travel. Planning guidelines are not strong enough to make this effective.


  In summary, Transport networks need to contribute massively to CO2 reductions and air quality improvement in the future if 2050 commitments are to be supported, and the crisis in premature death (especially amongst the youngest generation) caused by poor air quality is to be improved.




Prof. Whitmarsh’s presentation can be viewed here – Lorraine Whitmarsh Behaviour change and low-carbon transport


In a world where activities that generate high levels of CO2 are deeply ingrained and sustained over decades, behaviour change is needed. Car use has been broadly stable since 1995, while rail use has declined. Recent trends associated with digital working and localisation of supply chains are helpful but data showed that some 75% of us use the car for around two thirds of our travel despite widespread understanding of the issues.

The hierarchy and priority of ways to reduce CO2 are :-

  1. avoid the need to travel
  2. shift to less damaging modes of travel, and
  3. improve travel technology.

The opportunity to change behaviour is at maximum at the time of disruption to daily routine, such as house move, job change, route closure. The use of incentives to establish (more) sustainable travel can be by both ‘sticks’ and ‘carrots’ and by experimental urban planning initiatives such as road closure (by accident or design) but this needs to be sustained for up to 3 months to make change durable. Habits are the biggest barrier to behaviour change and lead to ‘tunnel vision’.

Methods to encourage behaviour change should be both downstream (information and advertising) and upstream ((economic measures, changes to available products and services and to the built environment). Measures that could be used include restricting vehicle access, road user charging, car share lanes, priority parking, flexitime and teleconferencing targeted at individuals, groups and organisations for maximum effect.

In questions, many felt trapped as a car user due to lack of alternatives. A commonly expressed view was that we need infrastructure/transport capacity to be put in place first, with early public involvement to galvanise support. Examples such a smoking and litter suggest that advertising, cost increases and law change are effective but restrictive measures need to be balanced by positive support towards a vision that has widespread support. The 2018 Green Paper consultation suggests there is such support. Examples of accidental road closures such as ER, big events and roadworks can change habits if the alternatives are effective.


In summary, behaviour change needs a disruptive event and effective alternatives over a sustained period to become ingrained.




Dr. Georgina Santos’s presentation can be viewed here – Georgina Santos Air pollution


The encouragement of diesel cars well over a decade ago was based on expected fuel efficiency improvement of 16%. However, diesel CO2 emissions are only 6% lower than petrol, and the air pollution consequences of an increase of 111% in particle emissions was not understood until 2012 when WHO identified diesel particulate emissions as carcinogenic. Diesel is still, generally, encouraged around the world by lower or equal excise duty and fuel taxes.

Particle emissions are now assessed to be 31% from the tailpipe (zero from EV) 45% from tyres and brakes, and 24% from road abrasion. CO2 emissions per km (expressed as a % of petrol engine vehicles) during operation is judged to be 80% for diesel, 76% for hybrids, 39% for plug-ins and zero for EV. The purchase cost of EV cars is significantly higher than for conventionally powered cars and would need to be subsidised by £5500 (at todays’ situation) to make lifecycle costs better than conventional cars. This is unlikely to be adopted so other means of improving CO2 and air quality must be found.

Road access pricing (congestion charging or CC) is widespread, with Singapore, London, Stockholm, Milan and Gothenburg leading. The example of London showed it was not a vote loser in mayoral elections, but the conditions for success were :

  1. an existing public transport network already used by 90% of the population and capable of carrying an extra load
  2. increased Public Transport services on day 1 of application, and
  3. a consistent high level of congestion throughout the day with a high level (40% in London) of trips inside the CC zone being associated with business travel.

These conditions for successful implementation of CC are not, however, present in Cardiff.

Workplace parking levies (WPL) are applied in Nottingham from 2011 at £387 car place per year (>10 spaces) with revenues hypothecated to public transport.

Mobility as a service (MAAS) is wrongly regarded as the solution and can do more harm than good. Cheap unregulated ride hailing companies are drawing use from public transport and more km are being driven. Regulation of this new industry is urgently needed.

Options for Cardiff to consider are :- WPL, increased public transport to be the backbone of the network, diesel bans from selected areas, clean air zones. However, the conditions for introducing CC are not present in Cardiff.

In questions, the ability of the bus network to raise its utilisation high enough to make a difference was in doubt, and light rail is regarded as the only realistic option as the backbone of the system. It was noted that charging does not deter high salaried individuals, the rest of us need a viable alternative!


   In summary, a public transport network (based on light rail in preference) must be capable of delivering up to 90% of trips, creating an efficient and effective alternative to car use if CO2 and air quality are to be improved at the rate needed. Given this, restrictions to car access can be applied.




James Ingram’s presentation can be viewed here – James Ingram Reducing transport emissions in London


The London transport network operates through a variety of modes and is partly owned, licenced and franchised, but is managed centrally. A 25 year horizon plan to improve service, support new homes and jobs and improve public health exists. TfL are now focussing on zero net CO2 by 2050 and achieving WHO pollutant levels by 2030 by increasing use of public transport, walking and cycling from 63% to 80% of trips by 2041.

Most of London today has high and illegal levels of NOX, especially when measured at the roadside, 50% originates from transport. CO2 from transport is not reducing sufficiently to ensure 2050 goals are met.

The Low Emission Zone (LEZ) with congestion charging (CC) using ANPR is small, covering the West End and City, but has had a big and immediate impact because it was accompanied by a simultaneous increase in public transport. Car use has declined, cycling increased and total traffic reduced by 50%, although the effect is less marked today. Non-compliant vehicles must either pay or divert to avoid the CC zone or avoid the trip altogether.

Expansion of the LEZ to the whole Greater London area for HGV and vans with a CC of £200 and £100 respectively if not compliant has had dramatic impact. Compliance levels increased quickly and pollution decreased to legal maxima; note that as compliance improves revenue will decrease! NOX levels will be reduced  to legal levels by 2020 by increasing the CC for cars by £10, introducing an Ultra LEZ with CC by vehicle type and age, and  retro fitting part of the bus fleet to EV Euro 6 level and introducing new conditions for taxi licence renewal ( compliance of taxis is only 12% at present) aimed at increasing overall compliance from 65% to 79%. Further enlargement (by a factor of 18!) of the ULEZ in 2021 to North and South Circular routes is being enabled now for 2021. However, even this is not expected to be enough to reduce pollution to below legal levels everywhere, further retro fitting of buses (9000!) and new methods of CC that vary by time of day, location and congestion are under review.

Local schemes, customised by borough and congestion based, exist for WPL, small scale LEZ and both partially and fully restricted areas for non-compliant vehicles, with pedestrian only zones in the Barbican and Hackney areas referred to.


In summary, the public transport network is being expanded and cleaned up to support further road access restrictions and CC. Despite this, achievement of 2050 CO2 and NOX targets remains a challenge.




The presentations from ARUP can be viewed here – Delivering clean air while meeting transport needs


Examples were shown of several UK locations. These involve extensive cross functional work to optimise networks.

The new housing development in York close to rail connections can achieve 30-40% fewer trips, enabled by developer funding to support new infrastructure, charging points and EV buses justified by a jointly agreed assessment of ‘damage cost estimates’ for the new development netting £3m over the s106 levels for a development of 2500 homes.

UK ports have a drive to improve CO2 and air pollution by improving power sources and vehicle route management on and off port land including rail use. Concerns over competitiveness are difficult to overcome.

Urban delivery studies of this low margin, low price per delivery mode are constrained by unavailability of suitable high capacity EV models. However, the risk of additional KM as a consequence of parcel consolidation cannot be ignored.

The Mobility Mosaic system to analyse traffic using GPS phone signals was described. Understanding how and where people travel in Victoria, Australia is the basis for infrastructure interventions. Changes to traffic routes can be initiated and adjusted quickly to disrupt existing flows and understand the short and long term implications, the Barcelona Super Blocks were referenced.

The trial of a free public transport service in Dunkirk was explained. Results were mixed, less walking and cycling and poor utilization on some routes were difficult to resolve. A move to a ‘competitive’ pricing model sustains revenues and provide sufficient motivation to change mode. Luxemburg will soon become the first country to introduce a free public transport network.


In summary, transport orientated development can create transport choice habits that will support 30-40% improvement in CO2 and air pollution. Commercial operations are plagued by competitiveness concerns if sustainable transport is not universal and enabled by widely available EV vehicles of all types. Models exist to evaluate the impact of interventions to improve traffic flows and design sustainable alternatives.




Points made during the open debate were:-

  1. Nudge is not enough. Regulation needs to be calibrated for effect, both restrictions and viable alternatives are needed.
  2. Increase fuel taxes to reflect environmental cost and encourage sustainable travel modes.
  3. Infrastructure and public transport options must precede development.
  4. EV is not enough.
  5. Nothing replaces a clear vision of what is required and a focus on achieving environmental improvement metrics.
  6. The existing real estate in the city is not able to support 2050 goals, this must be the job of new development and transport infrastructure.
  7. New development must be designed to change habits, once established new entrants will follow suit.
  8. Use estate agents to sell the public transport solution.
  9. Cllr. Caro Wild promised that ambitious plans would be published within weeks to combat what he acknowledged was a crisis.
  10. Cllr. Wild also was open to any suggestions for further work with the university. Prof. Morgan expressed the hope that all the city’s universities would be willing to contribute.


The outputs from three student focus groups analysing the debate can be viewed here – Output from student focus groups




  1. Car use has tripled over the last 50 years, we have created a car society.
  2. Poor air quality is responsible for a large rise in premature deaths from a wide variety of ailments particularly affecting the young and the old.
  3. Cardiff has the worst air quality in the UK outside London.
  4. There is no safe level of air pollution.
  5. CO2 reduction will not achieve 2050 goals unless the rate of reduction increases tenfold. Transport lags behind other sources.
  6. EV have zero NOX
  7. EV CO2 emissions are zero whilst in operation but lifetime emissions are handicapped by manufacturing methods and limited battery recycling.
  8. Habits are the biggest barrier to behavioural change in mode of transport.
  9. Disruption to habitual travel choice over a period can change modes of travel permanently.
  10. Cross city routes that avoid the city centre should be developed and prioritised.
  11. Diesel and petrol are not sufficiently discouraged. Price can alter choice, as shown by smoking, litter, sugar and alcohol campaigns.
  12. EV cars are expensive to purchase, have low range, are too slow to charge and lack a charging network. These disadvantages need to be overcome.
  13. Congestion charging and road access charging does reduce traffic levels significantly and quickly but does not deter those road users who can afford to pay.
  14. Conditions for success of road access charging are a public transport network with the ability to handle the extra load and a high and consistent level of congestion throughout the day. These conditions do not exist in Cardiff.
  15. Workplace parking charging is a viable
  16. Despite congestion charging, London remains above legal NOX levels in most areas.
  17. Expansion of the Low Emission Zone and electrification of the bus and taxi fleets in London will not resolve all the legal issues with air quality.
  18. Small scale, local, restrictions to vehicle access in polluted or critical areas should be developed by local political representatives.
  19. Development close to travel hubs can reduce trips by 30-40%.
  20. Low cost ride-hailing networks detract from public transport use.
  21. Reducing CO2 in commercial operations can lead to competitiveness issues if not applied everywhere.
  22. There is poor choice of electric parcel delivery vehicles and the business model is under strain in congested city centres. Consolidation can add km driven and does not solve the problem.
  23. Models using GPS signals can measure the impact of temporary or trial route restrictions to help plan alternatives.
  24. Free Public Transport is not necessarily viable. Competitive pricing is more effective.
  25. Given the relatively fixed nature of the built environment, and the progress made in energy production, transport must be the major source of future CO2 reduction.



David Eggleton

Cardiff Civic Society

October 2019