Regarding 'Car back'
(I have amended the guidance to include Branwen's point)
Unless the idea is to urgently let the driver behind pass because they are irate, shouting 'car back', especially in town, adds unnecessary tension to riders who may be unsure what to do. Also why 'car' back which de-humanises road users, better to say 'driver behind' if anything
Regarding 'Car back'
(I have amended the guidance to include Branwen's point)
Unless the idea is to urgently let the driver behind pass because they are irate, shouting 'car back', especially in town, adds unnecessary tension to riders who may be unsure what to do. Also why 'car' back which de-humanises road users, better to say 'driver behind' if anything