LONDON The United Kingdoms largest bus and coach operators have warned the British government that it risks missing key carbon reduction targets by failing to maximize the potential of buses and coaches to help tackle climate change.

Englands largest ground passenger transportation companies joined forces to unveil a plan for eliminating one billion car journeys during the next three years.

A poll published to coincide with the launch of the bus companies Greener Journeys campaign found that using public transport more often is seen by consumers as second only to recycling as the most realistic measure to help the environment.

The bus operators Greener Journeys campaign recommended a busload of policy initiatives designed to encourage modal shifting that would deliver 50 percent more savings in transport CO2 emissions than currently planned under existing government policies.

In their joint call for action, the bus and coach operators stressed that technological advances alone are not enough to achieve the carbon reductions required to tackle climate change, and modal shifting must be a key priority.

The One Billion Challenge was launched by senior bus and rail industry executives, including Sir Moir Lockhead, CEO of FirstGroup; Brian Souter, CEO of Stagecoach Group, and David Begg, the principal of Imperial College Business School and professor of economics.

The challenge issued by the executives says that if people switch from car to bus or coach for just one journey in 25 it would mean one billion fewer car trips on UK roads over the next three years.

The Greener Journeys campaign is calling for the government to:

Set targets for local authorities to encourage modal shift

Introduce a fairer tax regime for bus and coach passengers

Adopt a bus scrappage scheme to drive investment in low-carbon buses

Promote bus priority, park and ride and other measures to cut car commuting

Encourage bus travel to reduce "school run" traffic

Supporters of Greener Journeys plan to lobby government and other stakeholders to support the plan.

Greener Journeys was founded by Britians five largest bus-owning groups -- Arriva, FirstGroup, Go-Ahead, National Express and Stagecoach.