Many vehicles leave the right shoulder of the pavement due to brake failure.
improper interior inspections.
driver distraction.
lack of oil pressure.

driver distraction

Explanation:

Studies and historical data show that the major cause of this is due to driver distraction. When driving many times a driver may look somewhere other than the road and get distracted which accidentally causes the driver to steer outside of the right shoulder of the pavement. This can also be due to the driver becoming tired/sleepy after driving for countless hours or even making a quick maneuver due to oncoming traffic getting too close. Regardless, all of these fall under driver distraction.