It is difficult to distinguish the lane marker or road edge from road when the lane marker or road edge is covered with dust or sand.

It is difficult to distinguish the color of the lane marker from road.

There is something looks like a lane marker.

The lane marker or road edge is indistinct or damaged.

The number of lanes increases/ decreases or the lane lines are crossing (Driving through a toll plaza/toll gate, merged/divided lane).

There are more than two lane markers.

The lane marker is very thick or thin.

The lane marker or road edge is not visible due to snow, rain, stain, a puddle or other factors.

A shadow is on the lane marker or road edge because of a median strip, guardrail, noise barriers and others.

When the lane markers are complicated or a structure substitutes for the lines such as a construction area.

There are crosswalk signs or other symbols on the road.

The lane suddenly disappears such as at the intersection.

The lane marker or road edge in a tunnel is covered with dirt or oil and etc.

The lane is very wide or narrow.

The brightness of outside changes suddenly when entering/existing a tunnel or passing under a bridge.

The headlamps are not on at night or in a tunnel, or light level is low.

There is a boundary structure in the roadway.

The light of street, sun, oncoming vehicle and so on reflects from the water on the road.

When light shines brightly in the reverse direction you drive.

Road surface is not even.

The distance from the vehicle ahead is very short or the vehicle ahead drives hiding the lane line or road edge.

You drive on a steep grade or a sharp curve.

The vehicle vibrates heavily.

The temperature near inside mirror is very high due to direct sun light and etc.

The lens or windshield is covered by strange materials.

The sensor cannot detect the lane because of fog, heavy rain or snow.

The windshield is fogged by humid air in the vehicle.

Putting something on the crash pad and etc.