The Department for Transport stresses the need for people to plan their journeys, with an emphasis on trying not to share a vehicle with those outside their household or support bubble.
If that's not possible, the advice is to share transport with the same people each time. Other advice includes:
• Open the windows for ventilation and wear a face covering for the duration of the journey
• Consider seating arrangements to maximise distance between people in the vehicle, such as leaving some seats free
• Clean the vehicle between journeys, including door handles and other areas that people may touch
Full guidance has been issued for the public, employers and operators which can be found at https://www.gov.uk/government/publications/coronavirus-covid-19-safer-transport-guidance-for-operators