New York City ? Driving into the most congested half of Manhattan could become an expensive privilege under a wide-ranging city program unveiled Sunday to cope with the booming population and ease stress on the environment.

The package of proposals outlined by Mayor Michael Bloomberg focuses on the city’s transportation, energy, water and housing networks that in some cases already are strained beyond capacity by today’s 8.2 million people.

“Let’s face up to the fact that our population growth is putting our city on a collision course with the environment, which itself is growing more unstable and uncertain,” Bloomberg said.

The most controversial idea in the plan, from the mayor’s Office of Long-term Planning and Sustainability, is a proposal to charge motorists for driving into Manhattan below 86th Street on weekdays from 6 a.m. to 6 p.m. Trucks would be charged $21 a day and cars would be charged $8, on top of the city’s already expensive parking.

Officials say it would reduce traffic and pollution while generating money for other transit projects – nearly $400 million in just its first year.

It is similar to a system that London has used since 2003, and officials there say it has significantly reduced congestion.

The scheme, known as congestion pricing, is applauded by environmentalists and alternative transportation groups, but is politically tricky for New York City because it would have to be enacted by the state Legislature.