Ford plans to skip ‘Level 3’ autonomy and shoot right for Level 5, the highest level of car automation. The automaker decided to skip the midway point after it noticed a few of its engineers dozing while testing semi-autonomous vehicles.

Even with “bells, buzzers, warning lights, vibrating seats and steering wheels, and another engineer in the passenger seat” the engineers struggled to maintain situational awareness, according to Raj Nair, Ford’s chief product development officer.

See Also: Ford rolls out gas- and driver-less fleet of tomorrow

Nair said the more the engineers became comfortable with the self-driving tech, the less attention they paid to the road. This could be a major issue for automakers deploying Level 3 cars, which cede some control to the human driver.

“These are trained engineers who are there to observe what’s happening,” said Nair to Bloomberg. “But it’s human nature that you start trusting the vehicle more and more and that you feel you don’t need to be paying attention.”

Will loss of incremental improvements turn clients off?

Going straight to Level 5 may hurt Ford in the short-term, as competitors will be able to offer some self-driving functionality to customers that want it. However, the decision let’s Ford power on ahead with its driverless dream, which it aims to have on the road by 2021.

Ford said it would deploy a fleet of driverless vehicles in major cities in four years time. The cars will work similar to Uber, but without the driver. This should reduce the cost of the cab by at least half, since driver payment is the most expensive part of a taxi business.

The company also said it would sell the vehicles to customers, but details are thin.

Ford has shown how confident it is in the driverless future with a $1 billion acquisition of Argo AI, a small robotics and autonomous systems startup that held some of the hottest talent in the self-driving industry.