Auckland Transport chief executive Shane Ellison has resigned and will leave the job in June next year.
Ellison began as chief executive of the council-controlled organisation in December 2017.
"It is the right time for the board to consider new leadership for a new phase at AT," he said in a statement.
"The organisation has many opportunities and challenges ahead as it continues to improve road safety, support mode shift, and responds to the climate crisis.
"The past four years have been very rewarding, with significant changes and many challenges, and I look forward to what is next for AT."