More reasons to leave the car at home

In a recent report issued by Purdue University in the US, researchers found that parking spaces in and around large shopping centres and retail parks are playing a role in heating up urban areas and adding to water pollution.

Purdue University researchers surveyed the total area devoted to parking in a mid-sized Midwestern county and found that parking spaces outnumbered resident drivers 3:1 and outnumbered resident families 11:1. The researchers found that total parking area to be larger than 1000 football fields, which covers more than three kilometres.

Bryan Pijanowski, associate professor of forestry and natural resources at Purdue University, Indiana, said even he was surprised by the numbers.

"I can't help but wonder: do we need this much parking space?" he said.

Pijanowski believes the results are cause for concern; in part, because car parks present environmental and economic problems.

Professor Bernard Engel, a member of the team from Purdue University, used a computer model to estimate changes in water-borne runoff caused by land-use changes. Engel, who heads up the Department of Agriculture and Biological Engineering, said car parks are troublesome because pollutants collect on their non-absorbent surfaces and are easily carried away by rain.

"They are, for instance, a major source of water pollution," he said. "The problem is that they accumulate a lot of pollutants like oil, grease, heavy metals and sediment that cannot be absorbed by the impervious surface. Rain then flushes these contaminates into rivers and lakes."

"Heavy metals accumulate on parking lots from car batteries and even airborne fumes, a phenomenon called dry deposition. Also, since rainfall cannot penetrate parking lots, they generate large amounts of flowing water, worsening flooding and erosion and water pollution," said Engel.

In Australia, where using the car to get from A to B is a national pastime, and large urban shopping centres wear the number of parking spaces they have like a badge of honour, the environmental impact would be similar to the report findings from Purdue University.

According to Suzie Gutheridge, executive director of the Green Building Council of Australia (GBCA), which was established in 2002 with the mission to develop a sustainable property industry for Australia by driving the adoption of green building practices through market-based solutions, says that car parks are certainly one of the challenges ahead in greening new and existing buildings in Australia.

"The Green Building Council of Australia's Green Star, which evaluates the environmental initiatives of designs, projects and buildings based on nine categories including energy, water, management, indoor environment quality, transport, materials, land use and ecology, emissions and innovation rating system, has addressed this in a number of ways. First, it rewards projects that reduce the number of car parking spaces and provides smaller bays to influence people driving smaller or hybrid cars. It also rewards projects for reducing the potential of pollution in water running off from buildings and hard surfaces (including car parks) to natural watercourses."

Gutheridge says that one of the ways to prevent watercourse pollution in car parks is the use of sand filters, grassed swales and porous pavements. Green Star recognises and rewards projects for implementing these and similar initiatives.

Urban areas have a higher capacity to absorb radiation from the sun than surrounding areas, and according to the Purdue report these areas become warmer meaning car parks add to the 'urban heat island effect,' which can raise local temperatures 2–3°C.

Pijanowski says that while parking spaces are necessary, businesses could be more creative about using combined-use or shared parking lots, thereby saving construction and property costs while minimising land use. He also suggests that a different approach to development planning is needed which could mitigate the monetary and environmental costs associated with parking areas.

The GBCA has a similar attitude and believes that there needs to be more incentives from the government to support what they call an industry-driven movement.

"Green Star, while for individual buildings, promotes a number of environmental decisions regarding the property development, including proximity to public transport, is driving the rest of the industry to take up green building initiatives. Town planners are very keen to support the rise of sustainable buildings," she said.