We're all familiar with accounts of arrestees who managed to crawl into the front seat of a patrol car and drive off even though he was handcuffed. Let's review good tactics for transporting prisoners.
1) The suspect should be thoroughly searched not only for possible weapons and contraband but also for cuff keys, which can be easily hidden in the mouth, on the inside surface of a belt, under a watch or other wristbands, etc.
2) He should be handcuffed in back and snugly seat-belted in.
3) He can be cinched just above the ankles with a pliable hobble, with the loose strand of the hobble closed in the door to restrain his legs and prevent major movement.
4) He should be kept under continual surveillance during all stages of the transport. When two officers are involved, the passenger officer watches the suspect either from the front passenger seat or in back with the properly restrained prisoner, depending on department policy. If you are alone, adjust your rear-view mirror to best reflect the suspect.
For nighttime transports, some officers place a red bulb in the dome light, which helps illuminate the prisoner and any movement while not significantly interfering with the driver's view of the road.
Even prisoners cuffed in back cannot be safely considered to be reliably restrained and ignored, as savvy suspects may know how to "step through" cuffs to bring them in front and then may even be able to open them by using a comb or other commonplace improvised "key." Never underestimate an offender's determination or threat level.
And remember: the closer you get to your transport destination, the more relaxed and complacent you may be tempted to feel, while the suspect may feel increasing desperate to take action as he senses his window of opportunity steadily closing. The offender in this story made his move at the end of the ride, outside a police station.