Vehicular emissions are rising in nearly every European country, and across the globe. Because of increasing car and truck use, greenhouse-gas emissions are increasing even where pollution from industry is waning.
The 23 percent growth in vehicular emissions in Europe since 1990 has "offset" the effect of cleaner factories, according to a recent report by the European Environment Agency. The growth has occurred despite the invention of far more environmentally friendly fuels and cars.
High taxes on cars or gasoline of the type levied in Copenhagen are effective in curbing traffic, experts say, but they scare voters, making even environmentalist politicians unlikely to propose them.
Other cities have tried variations that require fewer absolute sacrifices from motorists. Rome allows only cars with low emissions ratings into its historic center. In London and Stockholm, drivers must pay a congestion charge to enter the city center. Such programs do reduce traffic and pollution at a city's core, but evidence suggests that car use simply moves to the suburbs.
But Dublin is more typical of cities around the world, from Asia to Latin America, where road transport volumes are increasing in tandem with economic growth.
Urban sprawl and cars are the chicken and egg of the environmental debate. Cars make it easier for people to live and shop outside the center city. As traffic increases, governments build more roads, encouraging people to buy more cars and move yet farther away.
The trend is strongest in newly rich societies, where cars are "caught up in the aspirations of the 21st century," said Peder Jensen, lead author of the European Environmental Agency report on traffic.