Even the world's fastest man can't outrun DARPA's latest robot, which has now been clocked at 28.3 miles per hour.
Built by Boston Dynamics, the Cheetah robot was already the fastest-ever robot on legs, but has now broken its own land speed record of 18 mph.
According to the International Association of Athletics Federations, Bolt set the world speed record for a human in 2009 when he reached a peak speed of 27.78 mph for a 20-meter split during the 100-meter sprint.
The aim of the project is to create a robot for use in emergency response, humanitarian assistance and other defense missions, which often involve difficult terrain.
"Cheetahs happen to be beautiful examples of how natural engineering has created speed and agility across rough terrain. Our Cheetah bot borrows ideas from nature’s design to inform stride patterns, flexing and unflexing of parts like the back, placement of limbs and stability," says DARPA program manager Gill Pratt.
"What we gain through Cheetah and related research efforts are technological building blocks that create possibilities for a whole range of robots suited to future Department of Defense missions."
DARPA intends to test a prototype on natural terrain next year, but for now Cheetah runs on a treadmill in a lab to allow researchers to monitor its progress, refine algorithms and maintain its moving parts.
The current version is powered by an off-board hydraulic pump and uses a boom-like device to keep it running in the center of the treadmill.
The improvements in speed over the last six months are down to improved control algorithms and a more powerful pump. There's a long way to go before it can match the 61mph recently clocked by the Cincinnati Zoo’s cheetah, Sarah, was recently clocked at 61 mph - but that's not the point, says Pratt.
"Modeling the robot after a cheetah is evocative and inspiring, but our goal is not to copy nature," she says.
"What DARPA is doing with its robotics programs is attempting to understand and engineer into robots certain core capabilities that living organisms have refined over millennia of evolution: efficient locomotion, manipulation of objects and adaptability to environments."