The Transport Politic tells the story of a new rapid transit corridor study in suburban Maryland, extending west from DC Metro's Red Line terminus at Shady Grove. Don't worry if you don't know the geography. Think of this, instead, as a Rohrshach test. There's a yellow option and a blue option, and the squiggly blue option has an additional optional squiggle in green. Which one would you rather ride?
For a line that has to wind through a classic suburban landscape of business parks and subdivisions laced with huge freeways, the yellow line is remarkably straight. Unfortunately, many of the densest destinations with the best ridership potential are on the blue line.
As a result, Maryland now has to choose between a direct yellow line that misses key destinations and a blue line that serves them but is maddeningly circuitous, especially compared to the freeway that this line would compete with.
There is no clearer example of this basic principle: Public transit's usefulness is determined by land use planning more than by transit planning. Once you've arranged your major land use nodes to form a squiggle, you've pretty much prohibited efficient public transit.
(Given the way it's been built, the best solution I can see here is some form of Bus Rapid Transit with multiple branching patterns, so that a main line could follow the yellow route with branches to serve the major dots on the blue squiggle as well as the green squiggle to Kentlands. It's not ideal, but no solution here will be as satisfactory or efficient as what you'd have if the big destinations on the blue squiggle were in a straight line.)
This is a textbook example of why rational long-range planning must think about land use and transport together, using a co-ordinating tool such as the Frequent Network strategy that I discuss here as it applies to another sprawling capital region, Canberra, Australia. It's also a textbook example of the first rule of transit-oriented development, which is: Be on the Way! If you want your development to have good transit, put it on a direct route between other places that either have good transit or will readily justify it. Such a principle, had it been in the backs of everyone's mind as this suburbia was being built, would have made high-quality transit possible without changing the overall density, or for that matter changing anything else that would matter much to people who live there now.
Map by the excellent graphics team at The Transport Politic