Measuring emissions: a prerequisite for air quality, nature, and health

Thanks to the increasing number of vehicles, the impact of traffic and transport is being felt everywhere. Air pollution and nitrogen emissions in particular are having an adverse effect on our living environment and on people’s health, something recognised by the World Health Organization in its standards on air quality and by the Dutch government and its ‘Schone Lucht Akkoord’, or clean air agreement.

‘Vehicles are not becoming cleaner “naturally”’, warns TNO’s Willar Vonk. ‘That is why the government is committed to making the norms stricter in the future and to improving testing procedures. And it’s bearing fruit too – Euro-6 lorries, for example, are now in many cases really clean, while the latest generation of diesel cars are just as clean as cars that run on petrol.’

Everyone should do their bit to tackle the problems associated with nitrogen

For many decades now, TNO has been measuring emissions by cars, vans, lorries, buses, mopeds, motorcycles, excavators, tractors, trains, and ships on behalf of the Ministry of Infrastructure and Water Management. This has helped us identify areas where improvements could be made to legislation, so that actual emissions by these vehicles can be reduced. However, legislation is very much a long-haul matter and the improvements it is intended to bring about only manifest themselves after a long period of time.

‘Everyone should do their bit to tackle the problems associated with nitrogen’

Vonk: ‘As far as the here and now is concerned, everyone needs to play their part in dealing with the problems of nitrogen. A lower speed limit on motorways is a good example – if everyone were to observe it, it would really have an effect. And so would properly maintaining vehicles, checks on emission levels in MOT tests, encouraging the use of clean and economical cars, and measures aimed at deterring the use of dirty and uneconomical cars or getting them off the roads altogether.’

Emission readings in relation to speed limit

The reduced maximum daytime speed limit on motorways of 100 km/h can be directly traced back to the emission readings taken by TNO. ‘We defined fifteen traffic situations, such as a main road, or motorways with and without speed checks’, explains Norbert Ligterink of TNO. ‘This enabled us to work out the average and the “ideal” emission level for each situation.’

Reducing speed limits still further is a bad idea, says Ligterink. ‘The most modern lorries in particular perform excellently on motorways. At 80 or 90km/h, they are extremely clean. But when travelling at 60km/h, their emissions increase by a factor of two or three. The same is true of modern diesel cars. Emissions appear to be substantially lower from vehicles on motorways moving at a constant speed than in any other circumstance.’

‘The reduced maximum speed limit of 100 km/h can be directly traced back to the emission readings taken by TNO’

Emission readings on the road

Because cars do not behave “naturally” on rolling roads, TNO carries out measurements on actual roads as much as possible. Ligterink: ‘We fit cars with sensors and units and send them out with their users. The data reaches us through the cloud, and we can simply follow the cars. We see where they go, how fast, in what weather conditions, on what type of road, and what emissions they are producing.’

‘It’s interesting to know that the number of really different types of engine on the market is fairly small. Around ten or eleven account for half of all cars on Dutch roads: after all, developing and running an engine factory is only worthwhile if you produce a million units every year. It’s not without good reason that various brands in the same group use the same engines.’

Focus also needed on fine particles in vehicle emissions

With regard to road traffic emissions, the focus lies on nitrogen oxides (NOx) and carbon dioxide (CO₂). Ligterink: ‘In addition, we are also the only institute in Europe that measures ammonia (NH₃) from both petrol and diesel-powered cars on the road. This is a new field of study, but we are keen to understand exactly what is involved, so that the right laws can be put in place.’