The first congestion pricing plan in the U.S. has begun, charging most drivers $9 a day to enter the lower half of Manhattan. The long-debated plan is projected to raise up to $800 million a year for the city's aging public transit system.

The program had defied many obstacles over the course of decades. It debuted over the weekend on what seemed to be a successful first day.

While commercial trucks entering Manhattan will be charged depending on the truck size and time of day, there are workarounds.

Congestion pricing could generate revenue many cities are desperate for, while simultaneously easing traffic and improving air quality. But legal challenges and President-elect Do