?The group, which includes the South Western Railway (SWR) and Great Western Railway lines, said it will continue to manage its rail franchises but warned that it has concerns over "risk and rewards" in the sector.
It added that it is waiting for the outcome of the Government's review into the rail industry and said "any future commitments to UK rail will need to have an appropriate balance of potential risks and rewards for our shareholders".
The firm - one of the largest operators in the UK with a fifth of the market outside of London - said it believes "now is the right time" to separate out its bus division, which it added has "limited synergies" with its other operations.
It said the formal sale process for Greyhound is now under way in a move to deliver "best value for shareholders".The group's break-up plans come as part of a move to focus on its North American businesses - the First Student school bus division and First Transit, which account for nearly two-thirds of annual earnings.
Matthew Gregory, the recently-appointed chief executive of FirstGroup, said: "We see significant potential to generate long-term, sustainable value and growth from the solid platforms these businesses provide in the North American mobility services sector."We are intent on executing this strategy at pace, having full regard to the regulatory and stakeholder procedures and approvals that will be required."