Motorcycles and Air Quality

This page forms part of a draft article about plans to permit motorcycles in bus lanes.

Synopsis

Croydon Health Authority and the Greater London Authority have both said that poor air quality kills many Londoners each year. Plans to make motorcycle use easier are likely to encourage more use of powered two wheelers (PTWs), yet Department for Transport (DfT) measurements show clearly that PTWs are far more polluting than cars...

Croydon's air quality

Croydon Health Authority has estimated that between 32 and 189 people in Croydon die prematurely each year because of air pollution (see Pollution In Croydon Annual Report 2001/2002. Because of poor air quality, Croydon Council was forced to declare Croydon town centre an Air Quality Management Area in October 2000, and this has now been extended to the entire borough.

Most people probably imagine that cars emit more pollutants than motorcycles. However, this is not so. Department for Transport data shows clearly that, for most of the major pollutants, PTWs are overwhelmingly more polluting.

Motorcycles and particulates

Particulate pollution is linked to reductions in lung function, with a corresponding decrease in oxygen to organs. A number of studies have linked particulate pollution to higher mortality. People most sensitive to particulates include children, the elderly, and those with heart problems or respiratory diseases such as emphysema, bronchitis and asthma.

The DfT's Transport Statistics 2005 31st edition, table 3.6 shows typical particulate emissions for motorcycles with a variety of different engine types. Per kilometre travelled in urban conditions, PTWs with 2-stroke engines typically emit 26 times the particulates as a modern car; motorcycles with 4-stroke engines typically emit 78 times the particulates. The diagram above shows the DfT data in graph form.

Motorcycles and carbon monoxide

Carbon monoxide is a poisonous, colourless, odourless gas. Even low levels of carbon monoxide can present a health risk to some individuals. People with heart disease, sickle cell disease, and anemia are among the most at risk from carbon monoxide. Age and general health may also affect susceptibility.

The DfT's Transport Statistics 2005 31st edition, table 3.6 shows typical carbon monoxide emissions for motorcycles with a variety of different engine types. Per kilometre travelled in urban conditions, PTWs with 2-stroke engines below 50cc typically emit 4 times the carbon monoxide as a modern car; motorcycles with 2-stroke engines greater than 50cc typically emit over 19 times the carbon monoxide, whilst those with 4-stroke engines emit over 11 times. The diagram above shows the DfT data in graph form.

Motorcycles and hydrocarbons

Benzene and 1,3-butadiene are among the hydrocarbons emitted in motorvehicle exhaust gases. Both are known to be carcinogenic. Other hydrocarbons emitted in lower volumes, but known to be highly toxic or carcinogenic, include PCBs and dioxins.

The DfT's Transport Statistics 2005 31st edition, table 3.6 shows typical hydrocarbon emissions for motorcycles with a variety of different engine types. Per kilometre travelled in urban conditions, PTWs with 2-stroke engines below 50cc typically emit 188 times the hydrocarbons as a modern car; motorcycles with 2-stroke engines greater than 50cc typically emit 458 times the hydrocarbons, whilst those with 4-stroke engines emit 48 times. The diagram above shows the DfT data in graph form.

Comment

The data above shows clearly that motorcycle and moped users are among the worst polluters on London's roads. Measures that make PTW easier, including permitting motorcycles in bus lanes, are likely to encourage greater use of motorcycles and mopeds, with a detrimental effect on air quality and community health. Croydon Cycling Campaign believes that measures that may lead to an increase is the use of PTWs, or that will bring PTW exhausts nearer to both cyclists and pedestrians, should be avoided.

Page updated: 29/08/2006