When leaders in Washington talk about investing in infrastructure as a way to stimulate the economy, most people think first of highways and bridges and roads. But President-elect Barack Obama's promise to focus on public works is an opportunity to advance on energy independence, respond to climate change and bring the nation's transportation system into the 21st century, writes Armando Carbonell, senior fellow and chair of the Department of Planning and Urban Form at the Lincoln Institute, in an op-ed essay appearing in today's editions of The Boston Globe. That means fixing existing roads and bridges instead of building new ones, and investing in streetcars, light rail and intercity rail within a coherent framework that links transportation and land use. Organizing the infrastructure investments in megaregions, such as the Boston-to-Washington corridor or the Pacific Northwest, would be preferable to cities and states competing for dollars, he writes. The Lincoln Institute has worked together with the Regional Plan Association on infrastructure planning and megaregions, under America 2050.