Heavy duty vehicles
Since heavy duty vehicles generally have diesel engines the improvements in engine technology have produced substantial reductions of NOx and PM up to Euro IV (2005/55/EC). From Euro V (2005/78/EC) catalytic converters for NOx and filters for PM will be necessary. The most recent upgrade to Euro VI is in force since 18 July 2009. The progress in emission control here is summarised in Table 2.
Table 2. Development of emission requirements for (engines of) heavy duty vehicles (trucks and buses))
| CO(g/kWh) | NOx(g/kWh) | HC(g/kWh) | PM(mg/kWh) | |
| Euro I (1992-93) | 4.5 | 8.0 | 1.23 | 400 |
| Euro II (1996-98) | 4.0 | 7.0 | 1.1 | 150 |
| Euro III (1999-2000) | 2.0 | 5.0 | 0.25/0.66 | 100/1601) |
| Euro IV (2005) | 1.5 | 3.5 | 0.46 | 20/301) |
| Euro V (2008) | 1.5 | 2.0 | 0.46 | 20/301) |
| Euro VI (2012) | 1.5 | 0.4 | 0.13/0.162 | 10 |
1) The two values refer to one of two admitted test cycles
2) For Compression ignition and Positive ignition engines respectively
The new Euro VI standard allows for the introduction of a limit value for particle numbers, in addition to the one for mass. Such a measure is meant to rule out the use of the less effective ‘open filters’. Also a provision is made for regulation of the maximal direct NO2 emission as percentage of NOx.
Future discussion
The gradual tightening of the Directives on both Euro standards is an impressive result of the combination of stimulated technological innovation and tenacious negotiations during several decades. Though further improvements might be possible it is realistic to consider that the technology development of the internal combustion engine with respect to emissions of the Euro standards may be nearing its endpoint. One reason could be that the start of another discussion, on CO2-emissions of vehicles, may interfere. It is known that several of the exhaust gas measures which have been or are presently introduced affect the fuel-efficiency of vehicles.
The benefits for air quality, in particular of the more recent legislation, may be felt in full well after 2025. Market penetration of the new technologies needs time; for heavy duty vehicles this time lag amounts to between 15-20 years.