The environmental impact of transport is significant because transport is a major user of energy, and burns most of the world's petroleum. This creates air pollution, including nitrous oxides and particulates, and is a significant contributor to global warming through emission of carbon dioxide.
Here are some action you can take to reduce carbon emissions:
Switch to public transport
Switch to riding a bike or walking
Switch to hybrid or electric car
Request to work from home where possible
Buy carbon offsets when you fly