Regensburg, Germany - Car passengers should try their best to stay awake during long car journeys or risk making the driver feel drowsy too.

Juergen Zulley, a sleep researcher and professor for biological psychology at Regensburg University, says when front or back seat passengers start nodding off, it automatically makes the driver feel sleepy as well.

“Figures show that the risk of falling asleep at the wheel and being involved in a road accident is much higher with a slumbering passenger than with an alert person who keeps the driver in good spirits,” said the expert.

Zulley said the relaxed regular breathing and inert posture of a sleeping person can lull a driver into sleep.

Road safety figures show that one in four fatal road accidents on German roads is caused by a driver momentarily nodding off at the wheel and losing control of the vehicle.

Zulley advised passengers and drivers to watch for the tell-tale signs of driver fatigue, such as excessive yawning. Occupants should insist on a long break so that the person in charge of the vehicle can rest before continuing the journey refreshed.