How many public hearings have you attended in which a development opponent or neighborhood organizer says he can't support 10 units an acre, but 6 might be acceptable? Or if 20 units an acre are proposed, maybe 10 would be OK. Do you think anybody in the room — including the activist — can actually imagine what the difference looks like?

Density, whether high or low, is not inherently good or bad. It all depends on the project and its environs.

The Massachusetts-based Lincoln Institute of Land Policy has a new website called "Visualizing Density." The website and an associated new book of the same name by Julie Campoli and Alex S. MacLean clearly endorse the concept of efficient land use, which means higher densities.

What makes the website and the book so fascinating, though, is the photos. They vividly illustrate that development, whether high-density or low-density, can be not only ugly but impractical. The number of units per acre is not a deciding factor.

Have a look for yourself. Planners, developers, housing advocates and academics may find these photos and other tools on the Visualizing Density website to be useful — especially when public hearings devolve into debates about units per acre. You'll need to register for the Lincoln Institute website, which is free. But if you're serious about land use policy, you should already be signed up because Lincoln does thought-provoking work.

- Paul Shigley