It wasn't that long ago that courts ruled that cops were legally permitted to pull drivers over and issue speeding tickets without verifying speeds by radar. Currently, if a police officer thinks your pedal is too close to the metal, that's good enough to turn on the sirens and nab you.
The fundamental problems with the "eyeball" test are obvious enough that we don't need to recount them here. And thankfully some lawmakers in Columbus are finally taking action so that Officer Barney will have to rely on more than his keen eye to make sure you're exceeding the speed limit.