Public transit is a powerful tool for addressing a huge range of urban problems, including traffic congestion and economic development as well as climate change. But while many people support transit in the abstract, it's often hard to channel that support into good transit investments. Part of the problem is that transit debates attract many kinds of experts, who often talk past each other. Ordinary people listen to a little of this and decide that transit is impossible to figure out.

Jarrett Walker believes that transit can be simple, if we focus first on the underlying geometry that...