Originally Posted by Drew Eckhardt

Road bikes are slow compared to time trial bikes.

Gibertini and Grassi measured CdA numbers of .304, .288, and .235 m^2 respectively for a 1.8 m tall cyclist riding in the brake hoods, drops, and in an optimal time trial position on aerobars.

Given flat ground, 75kg of bike + rider weight, and .004 Crr with those numbers a modest 200W should produce 21.7, 22.1, and 23.6 MPH respectively.

Skipping the anachronistic UCI diamond frame allows much greater gains.