For riders in New York City, who saw him join the M.T.A. at a time of crisis, he took on a larger-than-life persona (the “Train Daddy”) as the face of the effort to fix the subway.

Many hoped he could push upgrades to finally modernize the system’s antiquated infrastructure and bring subway performance up from all-time lows that prompted Governor Cuomo to declare a state of emergency in 2017.

What have been the highs and lows of his tenure? Did he achieve what he set out to do?

Mr. Byford has been widely credited for pushing the on-time performance for trains from 58 percent, when he took over in 2018, to over 80 percent through operational changes that focused on the basics, like upgrading subway signals.

He also put renewed attention on accessibility and tried to push the agency to be more accountable to its riders, both of which have had mixed success so far.

A lot of the ideas he has for further improving the transit system are outlined in the M.T.A.’s new $54 billion capital plan, so it will now be largely up to his successor to implement that vision.

It has been reported that there were tensions between Mr. Byford and Mr. Cuomo. How did their visions for the subway differ?

The M.T.A. is a highly politicized environment, and one of the trickiest parts of the subway chief job is that it is influenced by the whims of elected officials, like Mr. Cuomo, who controls the authority.