Dec 08 2014

1 The Environmental Audit Committee Evidence that is NOT in the Report



Further written evidence submitted by David Davies


(A)   Ref to: PEMS (Portable Emissions Measurement System) bus testing in Brighton, which may be helpful to the EAC for its current Air Quality Inquiry


This the most up to date and comprehensive testing on buses that has been carried out yet and could be extremely useful when considering strategy going forward.


This report confirms many of the things that I have been saying for a long time and perhaps they should now be given full and proper consideration


1/ That it is crucial to improve traffic flow; it seems that approx 90% of pollution is created in less than 10% of the drive cycle i.e. when the vehicle is pulling away from a stop at traffic lights or traffic congestion  or from slowing significantly. The testing that has been carried out clearly shows that the stopping of a bus at traffic lights causes a huge amount of emissions (see page 14 of the test report)

This is also true of any vehicle stop starting or slowing down due to traffic congestion and obstruction.


There are some simple solutions which could make a massive difference.

a/ A ban on peak time deliveries-HGVs are some or the worse polluting vehicles on the road and they cause the most pollution when they are stop starting in traffic. If they are banned at peak times this means that they will then be operating at a period when they will be stop starting much less and therefore the most polluting vehicles  will be polluting much less.

It also means that the remaining traffic (including buses and taxis) will flow more freely and therefore also cause less pollution.


b/ Improved enforcement of Red Routes- there are restrictions already in place which should stop vehicles stopping on a red route. However these restrictions are not rigidly enforced which means that delivery vans and trucks and also individuals often park with hazards on blocking traffic. This is inexcusable and severe enforcement needs to be implemented; perhaps an increased fine of £1000 for anyone caught obstructing traffic in this way and motorcycle enforcement teams co-ordinated by CCTV Operators to enable rapid response (most drivers do this knowing that if they are parked for 10 or 20 minutes the chances of being caught are slim ).


c/ Improvement of Traffic Light Signalling. Pedestrian crossings do not function properly so there needs to be an improvement in pedestrian traffic light signalling.

One solution for which the technology already exists would be to fit buses with transponders so that as they approach traffic lights the signal remains green.

It is quite often the case that a pedestrian will push the button to cross the road and then cross when there is a break in the traffic , which means that traffic then has to stop needlessly when the lights subsequently change.

A simple solution for this problem would be to change how pedestrian crossing traffic lights operate. Instead of the lights changing to red when the button is pushed a better option may be that the lights flash on amber for 30 seconds or a minute. It could be stipulated to drivers that if they see the amber lights flashing and there is a pedestrian waiting to cross they are obliged to stop allowing the pedestrian to cross, in much the same way that a Pelican or Belisha crossing works already. If the amber lights are flashing and there is no pedestrian then drivers can proceed at a slower rate with caution which will mena that they do not come to a stop and would reduce their emissions significantly. A separate operation of the button (perhaps holding the button for several seconds) could allow the lights to change to red for pedestrians with disabilities, the elderly or children.


d/The addition of footbridges and elevated walkways at high footfall crossing points- It could improve traffic flow significantly if pedestrian footbridges were installed at locations where very high footfall happens .

The configuration of these footbridges could vary at different locations. In Oxford Street in London for example perhaps an elevated pedestrian walkway could be constructed each side of the street with crossing points at intervals. This could create another level of store entrances for shopkeepers in much the same way that happens in a shopping mall. It could also free up  space at ground level which may enable cycle routes without further restricting traffic flow. Existing traffic lights could be left in place to enable crossing for those with disabilities. Advertising on bridges and walkways could fund the cost of building them


e/ Better management of Road Works. It is quite often the case that when road works occur they are not carried out around the clock. A better method for road works could be implemented by making sure that road works are carried out in a way which allows traffic to still flow at peak times. This could be achieved by temporary steel road panels being used at peak times and then lifted out of place to allow for road works to continue at off peak times. It could also be a requirement that debris from road works  which is often left in place (because it is needed to backfill) could be loaded into skips and positioned so that it does not restrict traffic flow.


2/ The report also confirms that the Euro standards CAN NOT be used as an indicator of the true emissions of a vehicle in real life drive cycles. The report shows that the Euro 4 bus creates less pollution than the Euro 5 bus. This has previously be confirmed in reports of testing carried out by the Environmental Research Group at Kings College London. This is probably caused by the fact that the OEM engine management system does not map the urban drive cycle in an effective way to allow EGR and SCR to function properly in an urban drive cycle. It should therefore be acknowledge that the concept that older vehicles are more polluting is false and that retrofit of older vehicles could be a much better strategy than replacement of fleets. It is also the case that the cost of retrofit is much less than vehicle replacement. It seem that the Flywheel /Gyro Drive technology is an excellent way of reducing emissions and improving fuel efficiency and for the same cost of a bus replacement perhaps 10 or more of these systems could be fitted.


3/ The technologies of Exhaust Gas Recirculation and Selective Catalytic Reduction are not achieving the reductions in emissions in real life drive cycles that have been demonstrated in lab tests.

The recent testing by the Environmental Research Group and the testing in Brighton showed that the real life reductions were at the very best half of that that had been achieved in a lab test. In fact there has been no consideration given to the much slower urban drive cycle (which means lower exhaust temperatures) and ambient conditions i.e. temperature and weather conditions. It has been shown in the report attached that the exhaust temperature is critical to the effectiveness of the SCR technology. If a bus is operating in the middle of winter and the air temperature is extremely low or there is water vapour in the air due to rainfall or snow then the Catalytic converter will never achieve a temperature at which it can operate.

This is proven by the increase in NO2 in air quality measurements during the winter period.


4/ Failure of Diesel Particulate Filters -. When Diesel Particulate Filters were introduced it was claimed that they had successfully reduced PM10 by a significant margin. This was true but what wasn’t known was the  PM10 had not magically disappeared. It had been broken down  in to PM2.5 which is actually MORE harmful than the PM10  because it is suspended in the air for longer and therefore over a wider area and is more harmful because it can be absorbed through the skin and lung lining. The Diesel Particulate Filters also created MORE NO2. When FULL FLOW DPF filters block they create back pressure which creates MORE pollution. This is why Full Flow Filters are removed; because they do not work in an urban drive cycle. Those who are campaigning to stop DPFs being removed need to understand the technical evidence and realise that the removal of FULL FLOW DPFs may actually reduce emissions


5/ Dangers of Unknown Emissions- We need to learn from history and make sure that technologies that are implemented are effective and that the ENTIRE situation is understood . The reason that the failure of DPFs was not understood was because initially the PM2.5s were not taken into consideration and measured. In exactly the same way the full consequences of Selective Catalytic Reduction have not been considered.

The process of SCR uses various catalytic coatings on the substrate. Testing in the US has shown that some types of coating and different types of diesel fuel can cause complicated chemical reactions which result in Dioxins and Toxins being created.

It is also acknowledged that ammonia slip can occur where unreacted ammonia based reductant  is emitted in the exhaust.

It is unknown exactly what and how much dioxins, toxins and ammonia is emitted and it is therefore impossible to measure.

What is known is that they exist and that is very small qualities they can be extremely harmful, in fact they could be more harmful that the NO2 that SCR is supposed to reduce.



It would seem that the best strategy going forward is a simple common sense approach. Post combustion technologies have been shown to be ineffective at achieving the reduction in pollution that is urgently required. Improved traffic management, cleaner fuel (as used in Sweden and detailed previously) and the rapid and extensive retrofit of technologies like the Flywheel/ Gyro Drive system will offer the best reductions in pollution.




1/The evidence of the ground breaking testing of buses carried out in Brighton highlights the need for a centralised office or department for air quality testing and policies.

The testing that has been carried out in Brighton would have cost tens of thousands of pounds and provides an excellent insight as to what direction policies and strategies need to take in order to effectively reduce pollution.

However there is currently no method of this information being expertly assessed or shared with local authorities throughout the country, and this valuable evidence would not be freely available elsewhere unless it is informally forwarded (as has been the case in this situation)

It may be a positive step if the Government or the Environmental Audit Committee were to set up a National Office or Committee which would collect technical and scientific information and then scrutinize it and formulate government approved strategies which local authorities could then use. This  national office or committee could be made up of experts who have conducted the testing , for example Professor David Carslaw of the Environmental Research Group at Kings or Sam Rouse, the senior scientist at the Air Quality team at Brighton Council and senior politicians who have experience in environmental issues.

At the moment most Local Authorities do not have the financial or technical resource to initiate and approve their own Air Quality strategies in an effective way which can lead to failures in air quality targets.

There is also a disconnect between the relevant Government Departments. The Department of Transport , DEFRA and the Planning Directorate often have situations where one, some or all of them may have jurisdiction over issues related to Air Quality. However there is no formal mechanism to establish which department has overall responsibility, especially in situations where there may be an overlap.

A centralised National Office or Department or Committee would enable a proper process which would make the best use of research that has been carried out across the country on many Air Quality subjects, instead of the current disconnected system which exists.

Once effective and viable strategies have been approved at a national level it will make it much easier for Local Authorities to implement successful Air Quality strategies and meet the required targets.



2/ A further piece of evidence which has come to light is the information below which shows that the volume of traffic in Central London has decreased by approx 23% in the 12 years since 2000.

It has been established by Air Quality measurements in London that there has been little or no reduction in pollution.

However because there has been a reduction in the volume of traffic by 23% this means that the pollution per vehicle has actually INCREASED by a similar margin.

This is further proven by the technical evidence and real world testing which showed that the newer Euro 5 vehicles created MORE NO2 than the 15 year old vehicles.

Since the Mayor of London improperly scrapped thousands of 15 year old taxis it should be of no surprise that the pollution has effectively INCREAED


This means that the current Mayor has not only failed to reduce pollution , he has actually made it worse because there are less vehicle which are creating about the same amount of pollution.

This is a direct result of his failed emissions strategies. The Taxi Age limit has scrapped older taxis and replaced them with newer MORE polluting taxis (as confirmed by the Mayors own evidence)

He has now proposed a 10 year taxi age limit. He has already made the pollution worse by implementing a 15 year age limit and now wants to make it worse still by scrapping even more of the less polluting older taxis.


The graph shows that the traffic in Central London has effectively reduced by about 23% in the period from 2000-2012 (the chart below shows a reduction from 100% in 2000 to about 77% in 2012) due to improvements in Public Transport by the previous Mayor



3 November 2014