"66 Parallel Trail" – I-66 west of Washington, DC. Outer 3+3 lanes free; inner 2+2 lanes HOV/Toll; center median possible future rail; bike/ped trail far right. It's better than I expected. Good pavement, gentle slopes, (literally) cool tunnels under ramps.
You're registering on Love to Ride USA, would you rather be registered on Love to Ride ? It's the same site, you'll just access more local information.