While congestion pricing is one positive step toward making New York City's transportation systems greener, Department of Transportation Commissioner Janette Sadik-Khan has even more ideas.

There are plans to pave the Big Apple's streets with recycled material, use less-polluting vehicles in the city's fleet and have the Staten Island ferry be powered by biofuel.

"There's no question there is a lot of room to grow," Sadik-Khan told the New York Post.