In 1803, Thomas Jefferson suggested to D.C.’s government that the broad Pennsylvania Avenue be lined with trees, in the manner of the elegant French gardens that he admired. The original street-section schemes, drawn by Nicholas King, are in the LOC’s collection, and thanks to Streetmix I’ve taken the liberty of updating them to imagine how they’d have evolved since then. Today’s configuration of Pennsylvania Avenue NW has wide sidewalks and double/triple rows of trees, and was designed and redesigned by various urban renewal commissions from the Nathaniel Owings Plan of 1964 through the the PADC up into the mid-1990s.
Option #1 was the then-road, a narrow dirt path.
Option #2 has a center gravel passage for horseback riders (today, cyclists?) flanked by two carriageways. I’m not sure how many roads of the day separated solo horse riders from carriages; perhaps the idea of having a separate center track was because an unburdened horse could travel considerably faster, and therefore should stay to the left of carriages. Nonetheless, the idea of a center track isn’t exactly new.
Option #3 has a broad carriageway flanked by two gravel footpaths, here reinterpreted as tree-lined cycletracks. Although this carriageway looks far too wide, today’s asphalt expanse is pretty much this wide — and ensures a relatively clear vista down the middle towards the Capitol (and Treasury, I guess).
I’ve illustrated Option #4 with a center transitway, although that seems like it would result in many conflicts between pedestrians/transit riders and cyclists.