Around 20% of accidents on multi-lane highways are the result of
driver fatigue. So the Japanese car maker Toyotahas developed a
system to rouse drivers before they quite literally drift off
completely. A camera watches the white lines on the road ahead
to determine if and how fast the car is veering towards or away
from them. An onboard computer then decides whether that kind of
manoeuvre is appropriate for the situation. If it is deemed
potentially dangerous, the system raises the alarm to wake the
driver. For example, a car regularly crossing white lines while
accelerating and braking is likely to be simply driving in city
traffic. But wobbling to and fro within a lane, or gradually
veering across white lines while moving at a constant high speed
may indicate a driver falling asleep on the open highway. If the
driver is judged to be losing consciousness, the computer raises
an alarm to wake the driver. Similar systems to warn when white
lines are crossed are already available in some cars, but this
system