Jack Roberts:

But, Freightliner engineers note, almost all of the Highway Pilot systems are in widespread use in fleets today. As startling and sensational as the thought of an autonomous truck may be, the fact is the integration and combination of these existing technologies are what enable autonomous vehicle control.
 Behind the wheel, enabling Highway Pilot is only possible when all the systems’ sensors are satisfied that safe operating conditions are present. The cameras, for example, must have clearly defined lane markers to track. The radar systems must have uncluttered acuity looking forward and the GPS system must have a strong signal and reliable information about the area the truck is operating in.
 If all those conditions are met, the driver is alerted via a message flashed onto the information screen directly in front of the driver. At that point, initiating the system is simply a matter of hitting the “Resume” button located on the right-hand spoke of the steering wheel.