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Measuring real-world emissions with TNO’s Smart Emissions Measurement System (SEMS)

In order to gain a clear picture of vehicle emissions and fuel consumption, it is necessary to test the vehicles in a large number of real-life situations. During the past few years, TNO has been developing the Smart Emissions Measurement System, SEMS for short, for that very purpose. SEMS is a highly compact sensor-based system that measures emissions and can be easily built into a vehicle. Because it is so compact, the vehicle in question can be used in the normal way while the measurements are being taken. This means that measurements can be taken over a longer period of time, making it possible to gather large quantities of practical data. Because of these characteristics, SEMS can be used by many different parties, such as consumer organizations, fleet owners, type approval authorities, and vehicle manufacturers. With a fleet of vehicles all fitted with SEMS, traffic emissions can be monitored in real-time and linked to the prevailing traffic situation.

Measuring emissions

As a result of dieselgate, everyone knows that car emissions can differ significantly from the readings taken during official type-approval tests. To overcome that problem, a real driving emissions (RDE) test has been added to the type-approval test. This involves the use of a mobile measuring system, the Portable Emissions Measurement System (PEMS). However, this certified system is costly and bulky, and an extra person in addition to the driver is needed, to carry out the test and to operate the system. As a rule, PEMS tests are therefore only performed for a limited time. As vehicle emissions and fuel consumption depend very much on the circumstances in which a vehicle is used, and how it is used, a short test will never be able to give a complete picture of its emissions behaviour. SEMS offers a cost-effective alternative that makes large-scale monitoring possible.

Monitoring emissions

The methodology behind SEMS gives a clear insight into emissions, and makes more effective emissions legislation and enforcement possible. In the future, it will enable the development of a type-approval test that can use on-board monitoring. This can be achieved by incorporating the technology and software used in SEMS into vehicles as standard, and by passing on real-world data automatically to the relevant approval authorities. The possibility of monitoring real-world vehicle emissions for longer periods of time, rather than simply measuring them, will help vehicle manufacturers gain a clearer picture of emissions in a range of circumstances, and will also enhance the effectiveness of existing legislation. It will ensure that exhaust gas treatment systems are sufficiently robust to be effective in all circumstances. The true winners from this further improvement in the monitoring of emissions will therefore be the environment and consumers.

TNO’s SEMS measuring system is about the same size as a carton of milk, so it takes up very little space. It means that cars can be used in the normal way during the monitoring process. This makes it possible to gather large quantities of real-world data about a vehicle’s emissions.

SEMS technology makes it possible to compare one vehicle to another

The power and intelligence of SEMS is found not just in the simplicity of the measuring system. The combination of the measuring system and the processing software makes SEMS unique. The data obtained using the sensors is sent wirelessly from the measuring system to a database, from where it is analysed and processed into valid statements about the emissions by the vehicle in a range of circumstances. Thanks to SEMS, vehicles can therefore be compared on the basis of emission data taken in real-life situations. This is information that will be useful to environmentally-aware consumers, for example, or to leasing companies wishing to make sustainable purchases, or public transport companies on the lookout for clean buses.

Our work

Emission factors for road traffic

The emission factors for road traffic are official estimates of vehicles’ average real-world emissions, broken down by type of vehicle, Euro class, type of road and traffic conditions. In the Netherlands,... Read more

Ir. Ronald van den Putte


Ir. Ronald van den Putte


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