Police added that they did not believe Williams was distracted by an electronic device.
Williams posted a message on her Facebook page on Friday saying she was "heartbroken".
"I am devasted (sic) and heartbroken by this accident," wrote Williams, the world's former top-ranked female tennis player.
"My heartfelt condolences go out to the family and friends of Jerome Barson and I continue to keep them in my thoughts and prayers."
Williams has said that the traffic light was green when she entered the junction and was stranded waiting for traffic to clear when the collision took place.
Mr Barson died nearly a fortnight after the crash after suffering internal bleeding, organ damage and a fractured spine.
Mrs Barson is seeking unspecified damages for pain and suffering, medical and funeral expenses, loss of earnings and companionship.