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The Euro 6 and Beyond

The Euro 6 and Beyond


The latest EU legislation on diesel engine emissions for new coaches and buses, as well as trucks, means that the fumes coming from the tailpipe of a Euro 6 diesel engine are cleaner than any of its predecessors.

At Arriva Bus and Coach, we sell buses and coaches, offer flexible rental packages, and offer a parts back up and coach repair service for the UK, so we obviously welcome anything that helps reduce emissions. Lower emissions, in this instance, mean a big reduction in NOx levels and less particulate matter (PM) being emitted. Oxides of nitrogen (NOx), and PM (soot particles, basically) are the two constituents in the exhaust system that the EU Commission deemed harmful and which needed to be reduced.

In many ways, Euro 6 is old news as all bus and coach makers have already brought their Euro 6 compliant products to market. The latest emission regulations were implemented in two phases. The first phase, that applied to new type approval vehicles, became law in January 2013; the second phase applied to new buses and trucks and meant that any registered from January 2014 on, had to be fitted with the Euro 6 approved engine. So, we’ve already seen the benefits these tighter controls have produced. Compared to the Euro 5 engine, for example, the Euro 6 produces 75% lower levels of NOx, with the PM reduction considerably lower, at around 95% of Euro 5.

The legislation for these kinds of pollutants coming from the exhaust pipes of bus diesel engines was first introduced in 1993, with the Euro 1. Since then, engine manufacturers have had to invest in new technology to reduce the levels of NOx, PM, and other harmful elements, with the result that there has been a huge reduction in emissions and a great improvement in air quality. Euro 6 is the latest – and some hope the last – on the journey to have ever greener coaches, buses, and trucks on roads across the EU. For the record, Euro 6 legislation means that all NOx emissions are reduced to 0.46 g/kwh (some 75% down on Euro 5 limits), and PM down to 0.01 g/kwh, but with added limits, this in effect means permitted levels of PM will be around 95% lower than Euro 5.

  • Stricter Regulations

    Euro 6 means there is a new procedure for certifying buses and trucks. There are also tighter rules for on-board diagnostics that monitor the diesel engine’s exhaust treatment to ensure that it is working correctly, and alert the vehicle operator if there’s a fault. As well as new regulations on tailpipe emissions, other changes with Euro 6 include:

    • A lower limit on ammonia emissions
    • A crankcase emission limit, where a closed system is not used
    • Improvements to the on-board diagnostics
    • Stricter emissions durability requirements for Euro 6 engines, up to 700,000 km, or seven years in the case of the largest vehicles
    • Introduction of a world-wide test cycle that includes steady-state and transient tests, which aim to reflect more closely how a vehicle performs during real-life usage.
  • Life after Euro 6

    As has already been said, bus engine manufacturers are up to speed with Euro 6 compliant products and there’s a widespread feeling – ‘hope’ might be a better way of expressing it – that if Euro 6 does what it’s designed to do, a Euro 7 won’t be necessary. To comply with Euro 6, manufacturers have had to invest billions and achieving the required standards has involved an enormous amount of effort, both in terms of R&D, as well as testing out on the road with vehicles.

    One of the main differences with Euro 6, compared to any previous legislation, is that now bus engines have to be shown to comply during real world usage, including at different temperatures and under various load conditions. So, if Euro 7 doesn’t appear to be on the immediate horizon, what is likely to happen next? There seems to be a general feeling among bus and truck manufacturers that the next target will most probably focus on getting CO2 emissions down.

    CO2 and other greenhouse gases are produced when fuel is burned, so the less fuel burned, the less CO2 produced – it’s that simple. Although everyone can agree that less CO2 is a good thing, the question is, how do you measure CO2 from a bus or coach? Because of the diversity and range of commercial vehicle applications, configurations and duty cycles, you can’t simply measure CO2 the same way you do for a car. A way of measuring will have to be found that allows for real-life bus usage, such as grams per person/km, for example.

    A key player in CO2 calculations could be the vehicle energy consumption calculation tool (VECTO), which can factor in drag, rolling resistance, and other elements to come up with a whole vehicle efficiency rating, similar to what we already see on tyres. EU regulation on VECTO is expected to be issued in 2016 and implementation, which will apply to coaches, is expected to be in 2017. Buses are likely to be included in 2018. Test cycles on emissions from diesel engines are becoming increasingly harmonised around the world; finding a universal test that applies to buses, coaches and trucks may still be some way off, but progress is definitely being made.