In its place is a 30-inch rumble strip that warns drivers they are too close to the track's edge.

The signs are used to warn drivers of people walking in the street.

Data from this could be used to warn drivers of unsafe conditions or inform maintenance planning.

This is to warn drivers that they are approaching the station.

When it is this low, roads may be closed, or lights and signs are turned on to warn drivers.

Their purpose is to warn drivers about what's approaching.

They would not only warn drivers about trouble but would be allowed to take partial control.

But the system could warn drivers with alarms or spoken words.

Should cars of the future simply do more to warn drivers or should they sometimes take over the controls?

The system would warn drivers of a possible collision with enough time to prevent it.