Road Transport Emissions

Exhaust legislation sets limits to regulated emissions, which include nitrogen oxides, carbon monoxide, gaseous hydrocarbons and particulates. Other emissions are called non-regulated emissions. The most significant road transport exhaust gas emissions are carbon dioxide (CO2), particulate matter (PM), nitrogen oxides (NOx), hydrocarbons (HC) and carbon monoxide (CO).

The most significant greenhouse gas is CO2, and its amount in emissions depends on fuel quality and fuel economy. In 2011, road transport represented about 16% of all greenhouse gas emissions in Finland.

To cut the road transport CO2 emissions, the EU introduced a CO2 emissions limit (130 g/km or 5–5.5 l/100 km) for new passenger cars coming into effect step by step in years 2012 - 2015. The EU´s target is  95 g/km for 2020. In 2013, the average CO2 emissions of new passenger cars in Finland were 132,4 g/km.

In Finland, passenger cars have an energy label familiar from household appliances. The use of the label is optional but recommended in Finland. The objective of the energy label is to allow car purchasers to compare the fuel economy and CO2 emissions of each engine option of each car model. At first, the energy label will be optional for the automobile trade, but the EU is preparing a new directive that would make the energy label obligatory for the sales of new automobiles.

In the long term, the motive power of the motor vehicle population will be based increasingly on alternative and more energy-efficient solutions. Vehicle technologies that reduce CO2 emissions include, for example, electric and hybrid electric vehicles. In fuels, the future trend will be an increasing use of renewable fuels or components. These include, for example, biodiesel made from vegetable oils, and ethanol.

Particulates are small liquid or solid particles created in the combustion chamber. The particles most hazardous to health are the so-called fine particles.

 In petrol vehicles, catalytic converters have significantly reduced particulate emissions as well as other regulated emissions. The particulate emissions of diesel engines have been reduced by developing fuels and engine technology, and particulate filters are becoming increasingly common in further filtering out exhaust gas emissions.

Nitrogen oxides are produced in the combustion chamber under high temperature and pressure, when nitrogen in the air is mixed with oxygen. The share of nitrogen monoxide in total nitrogen oxide emissions is about 90%, and the share of nitrogen dioxide is about 10%. However, in the atmosphere, nitrogen monoxide reacts to oxygen to produce nitrogen dioxide. Nitrogen dioxide is harmful for respiratory organs.

In 2010, the share of road transport in the overall transport particulate emissions was about 68%. The exhaust gas emissions of diesel vehicles contain more polycyclic aromatic hydrocarbons (PAHs) than those of petrol vehicles. Many PAHs cause cancer and genetic mutations.

Carbon monoxide emissions are the highest at slow speeds

The main source of CO emissions is old petrol-engine passenger cars. CO is a health hazard only in special environments, such as tunnels and parking facilities, where it cannot react to atmospheric oxygen and quickly turn into CO2.

About one half of Finland’s CO emissions are caused by road transport. In urban areas, a majority of CO emissions are caused by exhaust gas emissions from road transport. Catalytic converters reduce CO emissions significantly.

Old Automobiles Cause Majority of Emissions

In practice, catalytic converters became obligatory in petrol vehicles at the beginning of the 1990s, after which they have cut emissions significantly. Catalytic converters reduce NOx, HC and CO emissions by up to 90%. Nevertheless, on the roads of Finland, there are still hundreds of thousands of passenger cars that lack a catalytic converter and cause high emissions.