Not to mention nobody being in the intersection ILLEGALLY i.e running the red from the other direction. That's the factor that to me makes "timing" seem a fairly insane practice.
If no motorist who approached a red traffic signal would enter the intersection before confirming that the way was clear, a motorist running a red light would have to be more than two whole seconds late to cause an accident. By contrast, a motorist "timing" a (hopefully) green light may have no margin for error. Indeed, if the opposing traffic fails to clear the intersection for whatever reason (e.g. backed-up traffic, perceived debris in road, etc.), the motorist who tried to "time" the green light may cause an accident even if he judges the signal's timing correctly.