NOx emission

Last updated 21/04/2021
As part of the Danish Government’s Climate and Air-presentation as October 2018, the Government pledged to strengthen the initiative fighting trucks' fraudulent circumvention of the required NOx-limiting equipment.

The need to strengthen the initative against trucks' fraudulent circumvention of the emission-limiting equipment, is reasoned in the challenges identifying and proofing the illegal manipulation.

As part of the aggreement it was decided that the initiative against fraudulent curcumvention must encompass the development and implementation of control methods and use of tools to enforce the trucks to obay the regulation on limiting the air polution.

As part of the initiative a report was conducted within each of the subjects:


  • Mobile Remote Sensing
  • Use of SEMS (simplified Emission Measurement System) in combination with periodic inspection
  • OBD (On Board Diagnose) as control method
  • How the payload can influence the temperature of the emission system
  • Alternative test methods used in environmental control during periodic inspection
  • Stationary meassurement on heavy vehicles


Mobile Remote Sensing

Last updated 05/05/2021

Mobile Remote Sensing

The initial test qualified the use of Mobile Remote Sensing equipment (Plume Chasing) as a method to measure trucks’ NOx emission. The same vehicle was measured using both PEMS-equipment (Portable emissions measurement) and Mobile Remote Sensing equipment. The measurements proved that Mobile Remote Sensing equipment is suited to measure trucks’ emissions and to validate, if the emission limiting equipment is working as intended.

The second part of the test was conducted on the Danish motor ways in a corporation between the Danish Road Authority and the police. The equipment was tested through a 10-day period, and throughout this period the NOx emission from more than 500 heavy vehicles was measured. The test also validated the method of conducting a smart selection of vehicles for road side inspection of the emission limiting equipment.

Plume Chasing

The report demonstrates that Mobile Remote Sensing (Plume Chasing) can be utilized as selection tool during the inspecting of trucks’ level of NOx emission.

Heavy Duty Vehicle (HDV) NOx emission measurement with mobile remote sensing (Plume Chasing) and subsequent inspection of high emitters

The report resumes a 10 day testing of Mobile Remote Sensing equipment (Plume Chasing)

Employing SEMS-equipment

Last updated 05/05/2021

Employing SEMS-equipment in periodic inspection

A practical study has been conducted, testing the usage of SEMS-equipment. This study aimed to achieve a plausible method for measuring emission under periodic inspection, how the equipment should be installed on various makes of heavy vehicles, as well as to survey if a pilot test of 8 km could prove the emission limiting equipment to work as intended.

The study proved the use SEMS-equipment to be a valid method for measuring the NOx emission level for heavy vehicles.

SEMS equipment in connection with periodic technical inspections (PTI) of lorries

SEMS-equipment in relation to periodic inspection on trucks:
The report is study on testing methods that can be utilized to meassure the NOx emission during a periodic inspection of heavy vehicles.


Last updated 05/05/2021

OBD-equipment as control method for equipment limiting emission

The Danish Road Authority has conducted a control method built on OBD. This control method can be employed during periodic inspections of heavy vehicles to detect, if the emission limiting equipment works as required.

Application of OBD

The report describes the method, which build on OBD, which can be utilized to prove that the emission limiting equipment is functional. Furthermore, the method has been tested on a line of heavy vehicles.

The Payload

Last updated 05/05/2021

How the payload can affect the temperature within the emission system

During the Plume Chasing Project it has been indicated that especially unloaded trucks can have a high NOx emission despite of a well functioning post-treatment system. The high emission level is caused by a small load on the engine and hereby low temperature in the post-treatment system.

The effect of payload on the temperature of the SCR-system

The report highlights a field study of 5 heavy vehiclesl which emiossion systems have been equiped with an On Board Diagnose (ODB) surveillance under regular circumstances.

Alternative Test Methods

Last updated 05/05/2021
This study surveys alternative methods for improving the environmental measurement during periodic inspections. The study includes a survey from Denmark’s neighbouring countries, which maps out how they work to overcome the challenges of measuring the NOx emission.

Methods and technologies to support Periodic Technical Inspection of emission-controlled systems on heavy duty vehicles

The report encompasses a study on literature researching methods that can be utilized to meassure NOx emission in relation to periodic inspection of heavy vehicles.

Stationary Measurement

Last updated 05/05/2021

Stationary measurement of heavy vehicles

The report seeks to map out methods and technologies capable of being used for measuring the NOx after treatment system from a specific stagnant vehicle callled in for expection. The study has a specific focus on the trucks post-treatment system, and its’ usage during roadside inspections.

Stationary NOx measurements

This report surveys how NOx emission can be measured from a stagnant vehicle.