...researchers from the University of Maryland and John Hopkins have constructed a miniature robot with independent drive motors propelling its four whegs, which are hybrid-wheel-legs that offer the best of both.
The bot can travel up to 30 body lengths a second (2.2 m/s or around 5 MPH). As IEEE Spectrum points out, a human traveling the equivalent relative distance in the same time would be going approximately 120 MPH.