ULEZ stands for Ultra Low Emissions Zone, which is a scheme put into place in London to help reduce pollution. A ULEZ-compliant vehicle is one that meets the required Euro emissions standards for your vehicle and emission type. To be ULEZ-compliant, your vehicle must emit a sufficiently low level of exhaust pollutants, including nitrogen oxides (NOx) and particulate matter (PM) . The requirements for ULEZ-compliance are based on European emissions standards, which set limits on the amount of various chemicals emitted from a car’s exhaust pipe. To avoid a charge when entering the ULEZ, diesel cars must comply with Euro 6 emissions standards, while petrol cars must meet at least Euro 4 standards.