More than 5 miles per minute!
I would not have volunteered to operate the first locomotive on the new gauge.
This one was a total surprise to me. I'd known the rail gauges had been standardized over time, had no idea how rapid this was. Their methodical approach to get things set up for rapid transformation on a set day is where much of the time was spent saving time for the actual switch -- replace the wheels over a period of moths so they need only be flipped around and meanwhile can continue to be used on the old gauge, excellent idea.