Environmental zones, Euro norms and electric buses

Two things control the bus's relationship to air pollution: environmental zones, which determine whether the bus can even enter the major cities, and Euro emission standards, which determine how clean a diesel bus runs. On top of that comes electrification, which is changing both the bus, the working day and the safety requirements. Environment and traffic safety are part of the basic qualification's subject area on safety, service and environment.

Denmark has environmental zones in the five largest cities: Copenhagen, Frederiksberg, Odense, Aarhus and Aalborg. For heavy diesel vehicles over 3,500 kg — i.e. buses and lorries — the stricter environmental zone requirements came into force on 1 July 2020. The main rule is that an older diesel bus either meets at least Euro Standard VI or has an effective, approved particle filter retrofitted in order to legally drive in an environmental zone.

• 01The environmental zones are in Copenhagen, Frederiksberg, Odense, Aarhus and Aalborg.
• 02Heavy diesel buses (over 3,500 kg) must at least meet Euro VI OR have an approved particle filter.
• 03A bus that meets Euro VI is considered to meet the particulate filter requirement in itself.
• 04The control happens automatically via number plate recognition against the Motor Register — no sticker in the window.

Euro emission standards set how much a diesel engine may emit of, among other things, nitrogen oxides (NOx) and particles. For heavy vehicles the standards are written in Roman numerals (Euro I to Euro VI), whilst cars and vans use Arabic numerals (Euro 1–6). Euro VI is the current, strictest standard for heavy vehicles and is set in regulation (EC) 595/2009. The higher the standard, the cleaner the engine — Euro VI buses typically have both particle filters and SCR catalyst, which with AdBlue reduces NOx.

The jump from Euro V to Euro VI — in numbers

Limit values for heavy engines are given in milligrams (or grams) per kWh engine work, measured over fixed test cycles. Euro V was measured on the stationary ESC and transient ETC cycle, while Euro VI (Regulation (EC) 595/2009 with implementing regulation (EU) 582/2011) is measured on WHSC (stationary) and WHTC (transient). The cycles are not identical, so the figures cannot be compared one-to-one — but the leap is significant, especially for NOx:

For the driver, Euro VI means that the emission system must work: if the AdBlue tank is empty, or if SCR/particle filter is faulty, the bus can go into emergency mode — and a faulty system can make driving in an environmental zone illegal. Therefore, AdBlue level and engine warning light are part of the departure check (see that article).