In addition to being significant pollutants in their own right, VOCs and nitrogen oxides react in sunlight to produce a third pollutant — ground-level ozone in the smog. Transportation also contributes sulphur oxides (SOx), particulates, and chlorofluorocarbons (CFCs), the latter from air conditioner leaks and blowing agents used in vehicle manufacturing.
Vehicle exhaust emissions are a major source of air pollution in some areas, particularly around busy road corridors. Pollutants include carbon monoxide (CO), nitrogen dioxide (NO2), benzene, and particulate matter.
Air emissions from transportation are linked directly to health problems in the form of bronchial and lung disorders, urban smog, with its attendant damage to vegetation and human health, global warming, acidic deposition, and ozone depletion.
Heavy metals and petroleum products from vehicles can contaminate the land and stormwater. Transport is also responsible for some of the extensive heavy metal contamination of some harbours and estuarine areas.
Contaminated stormwater can make receiving water unsafe to swim in, drink, or collect shellfish. Culverts for transport infrastructure can disrupt fish migration. Suspended sediments, from road works for example, can affect water clarity, favouring species that prefer cloudy conditions.
Transport allows urban expansion, which can consume or damage valuable agricultural lands, natural habitats, and wahi tapu. Urban expansion can create inefficient travel patterns and congestion. Habitat fragmentation by roads or rail tracks can lead to biodiversity losses, and provide corridors for the spread of pests and weeds.
On the input side, transportation affects the environment directly by using land. Transportation systems require a significant amount of land, and land used in transportation is rarely usable for other purposes.
Noise and vibrations can affect people who live or work near busy roads, rail facilities, ports and airports, or under flight paths. This can cause stress, exacerbate existing medical conditions and interfere with daily activities such as communicating or sleeping. High levels of noise can depress property values.
5. Material Consumption:
Transportation also draws on the natural environment indirectly by using products from the energy, minerals, and manufacturing sectors, which draw their raw materials, such as non-renewable mineral resources, from the environment.
From a sustainability point of view, by far the most worrisome resource used by transportation is energy.
Since the Second World War, virtually every transportation mode has made impressive gains in fuel efficiency, and more gains are expected in the future.
7. Spills onto Land and Water:
Spills include the relatively infrequent but sometimes catastrophic accidental discharge of hazardous materials during transport, including, ironically, spills of oil used to fuel transportation in the first place.
Spills also include the deposition and run-off of toxic material from vehicles themselves.
8. Solid Waste:
Another category of transportation-related stress is solid waste associated with old vehicles and the construction of transportation facilities. Many metallic components of vehicles are recycled or reused, but non-metallic items such as plastics and rubber tires pose greater difficulties.