The requisite methodology is stipulated by the Task Force on Traffic and Transportation (in which PBL Netherlands Environmental Assessment Agency, TNO, Statistics Netherlands (CBS), and Rijkswaterstaat (RWS) are represented) and is reported internationally.
Emission factors are determined by the GCN/GDN consultative body, a partnership supervised by the Netherlands National Institute for Public Health and the Environment (RIVM), which involves several ministries, PBL, TNO and RWS. These emission factors are updated annually (based on state-of-the-art expertise) and published in mid-March, in accordance with Article 66 of the Air Quality Assessment Scheme. Emission factors are used in the development and monitoring of environmental and air quality policies at local authority, regional and national levels. Local authorities are obliged to use that data to perform local air quality calculations.
In advance of the introduction of a new Euro class, TNO prepares estimates of the anticipated emissions for all vehicle categories. Since, prior to that introduction, few if any vehicles are available on the market, these emission factors can not be determined on the basis of emission measurements. Accordingly, this is initially based on various sources of expertise, such as lessons learned, expert assessments, references, and any measurements obtained using prototypes. Once the emission standard has come into force and vehicles have become commercially available, TNO carries out emission tests on a range of vehicles. Based on the results of these measurements, the emission factors are then calculated. In this way, the emission factors for various Euro classes have evolved over the years as they are periodically adjusted in keeping with state-of-the-art expertise.
The high, real-world NOx emissions of Euro 5 and 6 diesel passenger cars and vans in particular, as revealed by the measurement programmes, have been – and continue to be – taken into account when determining the Dutch emission factors.
In parallel to its work in determining emission factors, TNO conducts a series of studies in support of Dutch emission registration. These involve studies into issues such as fleet composition (including the inflow and outflow of vehicles), changes in driving behaviour, and specific aspects relating to emission.
You can find the latest reports on emission factors for road traffic below.