Cannondale's SAVE (Synapse Active Vibration Elimination) system in its forks and hourglass-shaped chainstays, designed to reduce high frequency vibrations from the road.

The way they shape these parts helps quell the bumps in the road. My experience is not based on scientific tests just a seat of the pants observation based on riding various bikes. It takes a major road deficiency to make things uncomfortable on my bad boy and for a fully rigid aluminum bike that is saying something.