Sustainable transport refers to the broad subject of transport that is sustainable in the senses of social, environmental and climate impacts and the ability to, in the global scope, supply the source energy indefinitely.
Transportation sustainability is largely measured by transportation system effectiveness and efficiency as well as the environmental and climate impacts of the system.
Transport systems account for between 20% and 25% of world energy consumption and carbon dioxide emissions. Greenhouse gas emissions from transport are increasing at a faster rate than any other energy using sector.
Established alternatives to the conventional petrol powered automobile include public transit (buses, trolleybuses, trains, subways, monorails, tramways), cycling, walking, rollerblading and skateboarding.
Bike sharing systems operate in Europe in cities such Copenhagen, Amsterdam and London and in the US in cities including San Francisco, New York and Seattle. It is not compulsory to wear cycle helmets in these cities, which is an impediment to the spread of bike sharing in New Zealand.
An emerging alternative is personal rapid transit, in which small, automated vehicles would run on special elevated tracks spaced within walking distance throughout a city, and could provide direct service to a chosen station without stops.
All of these alternative modes of transport pollute less than the conventional automobile and contribute to transport sustainability. They also provide other significant benefits such as reduced traffic-related injuries and fatalities, a reduction in space needed for parking and driving, reduced resource usage and pollution related to both production and driving, increased social inclusion, increased economic and social equity, and more livable streets and cities.