How to get recall ! Help!

 Does anyone out there solved the problem of poor recall. Our new dog -male approx 2 yrs old border collie cross is seriously  worrying us .  He is a rescue (our eighth) and only comes back when he is good and ready. We have had him eight weeks and was doing well to start with on recall but yesterday he took off from the field and ran into traffic ignoring calls to come- could have been fatal. We have consulted a dog behaviourist but not sure if this has been much help. His recall  has deteriorated over the last couple  of weeks. Any  advice would be appreciated.