| Topic: | Official version of leaked draft report now issued by Defra | |
| Posted by: | Tim Henderson | |
| Date/Time: | 20/05/13 22:33:00 |
| The proper version of the real world emissions report from the 2012 monitoring in the City and Ealing has now been released at http://uk-air.defra.gov.uk/reports/cat05/1305201434_130514_DefraRemoteSensingReport_Final.pdf It clarifies the comments on how apparently poor the SCR system was on the tested buses by noting that TfL are now changing from the original equipment manufacturer devices to units optimised for London conditions. The optimised buses didn't go past the sensors last summer. It is hoped that the similar information from the Putney trials will show improvement..... " d The survey results presented in this report include TfL buses fitted with Selective Catalytic Reduction (SCR) systems which are all OEM (Original Equipment Manufacturer) systems. OEM SCR systems have been designed to pass Euro emission standards rather than being optimised for urban-type (i.e. low speed and low engine temperature) conditions. There is little evidence that OEM SCR fitted to buses, including hybrid buses, appreciably reduces total NOx during urban driving. TfL has a programme of retrofitting SCR systems and purchasing new buses where the SCR systems will be optimised for urban NOx reduction and where substantial reduction in NOx (up to 88%) is expected. No TfL buses with retrofit SCR were assessed in this report." and " In case of the OEM SCR systems used to ensure TfL buses meet the relevant Euro standard, the limited reduction in total emissions of NOx and the wide (but consistent) variation in emissions of NO2 needs to be better understood given the important future impact these technologies could have on emissions from vehicles more generally. However, the systems tested were not optimised for urban NOx reduction. Recent initiatives by TfL such as the development of an optimised SCR system for retrofitting 900 buses will be important to evaluate under in-use conditions. For example, the analysis of the impact the targeted used of these vehicles at locations such as Putney High Street (Wandsworth) would help confirm the emission characteristics of these vehicles." |