Diesel: Euro 4(PM) means that the particulate aspect of the set Euro standard needs to be met. This means that a diesel particulate filter can be used to bring a pre-Euro 4 vehicle to meet the Euro 4 standard to enable access into the zone. This means that:

• A Euro 4 diesel vehicle can enter the zone.
• If the zone affects cars or vans, then a Euro 3 diesel car/van can fit a diesel particulate filter to reach the Euro 4 standard, and enter the zone.
• For heavy duty vehicles, diesel particulate filters are often available to bring a Euro 2 or even Euro 1 vehicle to reach the particulate aspect of the Euro 4 standard.

For more information on which countries allow what retrofits, please see our which retrofit is valid page.