In order to be accredited as a Low Emission Bus, a vehicle must achieve WTW GHG emissions savings of 15% or more compared with an equivalent Euro 5 diesel bus with an identical maximum passenger carrying capacity. The bus must also achieve the Euro 6 emission standard.
The accreditation procedure is to be carried out in two stages:
Stage 1: Whole Vehicle Testing
A whole vehicle test is first undertaken to measure the Tank-to-Wheel (TTW) GHG emissions (reported as CO2eqv.) and energy consumption of the potential LEB, as well as NOx and PM emissions (to determine compliance with Euro VI). A bus will be placed on a chassis dynamometer and will run a series of simulations that mimic real world operating conditions for buses, with the exhaust emissions collected and analysed.
The test must use the new LowCVP UK Bus test cycle, which incorporates the old Millbrook London Transport Bus (MLTB) test cycle (the 159 London bus route) and a new section to reflect rural conditions, or an equivalent test cycle. If an alternative test is used, it must be based on similar average speeds as the LUB test, as well as the same number of stops per kilometre. Any non-LUB test cycles must be approved in advance by the Department for Transport.
The LowCVP UK Bus test cycle was developed by the Partnership with a selection of stakeholders to address previous concerns that the MLTB test cycle was too city-centric. The additional section at the start of the test simulates the conditions that a bus would face if operating on a more rural route; on hills, at higher speeds and for longer durations at higher speeds. To find out more about the MLTB bus test, click here.
Stage 2: WTW GHG Emissions Calculation
The WTW GHG emissions are determined by combining the TTW emissions derived from the whole vehicle test and a Well-to-Tank emission factor applicable to the fuel used to power the bus. The WTT factor can be supplied by the manufacturer to reflect a specific production pathway e.g. biomethane produced by the anaerobic digestion of animal slurry, or use a default value specifically selected by the LowCVP for the LEB accreditation procedure.
The Well-to-Tank and Tank-to-Wheel will be combined to give an overall Well-to-Wheel grams of carbon dioxide equivalent per kilometre figure to provide the basis for funding eligibility.