Veteran bus driver Robert Reid took his eyes off the road for just a moment to wave at a colleague who had let him through a busy Sydney intersection.

That simple, polite gesture at the start of peak hour ended the life of publishing executive Christine Mulholland.

Emergency services work to free Christine Mulholland, who died after being hit by a bus on Clarence Street. Credit:Sahlan Hayes

Mr Reid, a Sydney bus driver with nearly two decades' experience, saw a fellow driver flash his lights to let him through the intersection of Clarence and Erskine Streets on the afternoon of January 29 last year, and looked over and waved.

He drove through the intersection and hit 52-year-old Christine Mulholland, leaving her trapped underneath the bus for hours. Ms Mulholland died later in hospital.