MinnMan

Don't know about 2 wheelers, but my recent entry into this world shows me that trikes are much slower than DF road bikes. On my Catrike Eola, I work hard to get above a 15 mph average over terrane that is fairly flat, whereas on the same route I could do 18 mph on a road bike without too much effort and 19-20 if I work at it. Part of the difference is that I"m not fully adapted to the different muscle demands of the trike. I think I could get a little faster after a time, but not dramatically so.

Wheel size matters, btw.

In addition to being intrinsically slower, I find that the lower maneuverability and visibility reduces my average speed. I can't whip through turns and corners on the trike. If I see a traffic light that's about to go from green to yellow, on the road bike I can add power and accelerate through before the light turns red. On the trike, both visibility and the lack of accelerating power mean that I'm going to stop.

If you care about speed, probably a 2 wheel recumbent is a better bet. The trike has its place, though, and is kind of fun.