The head of Lothian Buses is to step down after four years at the helm.
Richard Hall said the "operational intensity of running public transport is extremely high" so it was time to leave.
The managing director will step down after the Lothian Buses' next board meeting on 5 March.
Nigel Serafini, Lothian's commercial director will stand in as interim managing director until his successor has been appointed.
Mr Hall said it had been a "tremendous privilege" to be Lothian's managing director.
"Lothian has been a huge part of my life over the last four years," he adde.d
"Our business never sleeps, we deliver for customers 24/7, 365 days of the year and that operational intensity of running public transport is extremely high and the time has now come for me to take on a new challenge.
The firm's chairman, Jim McFarlane thanked Mr Hall for his "significant contribution" to Lothian Buses.
"Under his leadership Lothian has seen significant geographic expansion of the business in addition to growth in customer numbers, revenues and profit," he said.