The Low Emission Zone (LEZ) extending through most of Greater London will be changed on 3rd January 2012. It is being tightened for all lorries, coaches and buses. Large vans, minibuses and specialist commercial vehicles will be also included for the first time. Affected vehicles will need to find ways to reduce exhaust emissions to comply with Euro 4 requirements. Previously the London LEZ required vehicles to comply with Euro 3 exhaust emissions. Vehicles that do not meet the emission standards can still travel within the LEZ but must pay a daily charge; a penalty charge notice is issued to owners for non-payment. The LEZ is separate and much larger than the London Congestion Charging Zone. Various LEZ’s are in force in cities across Europe, each with their own emission targets and deadlines.
Options available to operators to avoid LEZ charges include replacing older vehicles, reorganising fleets so that only compliant vehicles travel into the LEZ, or fitting an exhaust particle filter. The exhaust filter must of a design approved by Transport for London (TfL). Once an exhaust filter has been fitted, the vehicle requires a VOSA issued Reduced Pollution Certificate which is valid for two years.
Exhaust filters are the cheapest available option. Several UK manufacturers are approved by TfL. With the larger exhausts, diesel particulate and nitrogen oxide filters are squeezed into the cramped coach and bus engine compartments, and will run hotter than the original exhaust system. Therefore, we may start to see more exhaust DPF related failures, or ignition of poorly retained soundproof insulation etc. A mechanical failure, such as a turbo oil seal leak, could release engine oil into the exhaust and is also likely to cause overheating in the DPF and a potential fire.
Several of the DPFs available require regular cleaning depending on the operating conditions. Modern diesel fuelled vehicles fitted as standard with a sealed DPF can undergo an electronically initiated regeneration process, increasing the operating temperature and burning-off excess soot. Several of the conversion filters for Large Goods and Public Service Vehicles do not have automatic regeneration capabilities and require disassembly and manual cleaning. Failure to adhere to the maintenance schedule can cause the DPF to run excessively hot and could pose a risk of fire. The soot build-up on the DPF is likely to be higher if the vehicle spends long periods of time traveling at slower speeds or with the engine idling (such as with school run buses).
Several of the after-market filters use electronic backpressure recording. Manufacturers of these systems recommend that if fitted, the filter backpressure be recorded during the maintenance inspection to help identify changes in filter backpressure.
