Some states and cities are already experimenting with congestion pricing on major highways, where drivers can choose the free lanes or those that carry a fee.
"Using economics to influence public behavior is something this country is built on — it's called capitalism," Bloomberg said. "Tax policy influences you to drill here and mine there, and grow this and live here and do that."
Back in January, the mayor, who also has a home in London, said the congestion pricing system there did not appear to be working as well as expected.
London officials say charging drivers has helped relieve congestion, but the fee — equal to about $16 per trip — has gone up since its implementation in 2003. "I think their experience has been that people adjusted to the charges," Bloomberg said then.
When asked about Bloomberg's shift, his spokesman Stu Loeser said Friday the mayor's Office of Long-term Planning and Sustainability has been researching the issue and other ideas.
"What's changed is we've been going through months of study; there's been cumulative tens of thousand of hours of work on this," Loeser said.
Implementing congestion pricing would have to be done by the state Legislature in Albany, and many lawmakers who represent the bedroom communities outside New York City would balk at the idea.
"It's up to the Legislature, but I'd fight like heck to make it," Bloomberg said.
The idea is also unpopular with average New York voters, who said in a poll earlier this year that traffic was a problem but that they did not want to pay more fees.