I remember reading objections to the Phoenix light rail which amounted to "no one will ride it in summer when it's hot." It's quite possible that when summer rolls around fewer people will ride, although the real point is that plenty of people in Phoenix already took public transportation in the summer. Those bus riders didn't just disappear. Sure riding a lovely air conditioned car might be the choice of those for whom it is... a choice. But not everyone owns a car,
even in Phoenix.
"We topped our previous two months, in terms of, just, purely the number of riders," said Metro Public Information Officer Hillary Foose. "We reached about 972,000, which is equivalent, or results, in an average weekday ridership of about 34,000. Saturday ridership of about 28,500."
Very generous estimate of a capacity of a lane of highway is 2000 vehicles/hour.