Blind spot (automobile)
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Blind spots, in the context of driving an automobile, are the areas of the road that cannot be seen while looking forward or through either the rear-view or side mirrors. Blind spots can be eliminated by overlapping side and rear-view mirrors, or checked by turning one's head briefly, or by adding another mirror with a larger field of view. Detection of vehicles or other objects in blind spots may also be aided by systems such as video cameras or distance sensors, though these are not common in automobiles sold to the general public.
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Blind spot areas
The areas most commonly referred to as blind spots are the rear quarter blind spots, areas towards the rear of the vehicle on both sides. Vehicles in the adjacent lanes of the road may fall into these blind spots, and a driver may be unable to see them using only the car's mirrors.
Other areas that are sometimes called blind spots are those that are too low to see behind and in front of a vehicle. Also, in cases where side vision is hindered, areas to the left or right can become blind spots as well.
Elimination or checking of blind spots
Proper alignment of mirrors on most vehicles can eliminate these blind spots, but they cannot be eliminated on all vehicles, such as those that lack a passenger-side mirror, or that have no rear-view mirror. When mirrors are not or cannot be aligned properly, these blind spots must be checked by turning one's head. Some driving schools may require a head-turn, so that the instructor can easily observe that the student checked before changing lanes.
Mirror alignment is often done incorrectly by drivers. There is a tendency to want to provide context for the side mirror view by having the rear of the driver's own vehicle in the mirror frame. When properly aligned the side view mirrors widen the perspective offered by rear view mirror, not overlapping it at all.
Even with a head-turn, the driver should continue to look forward, in the direction the car is travelling. This is accomplished by using peripheral vision and only turning the head approximately 45 degrees. Exaggerated head-turns, where the driver actually faces backward for a moment to check the blind spot, are dangerous because the vehicle in front may come to a sudden stop just at that instant resulting in a rear-end collision.
Failure to check one's blind spots, especially before changing lanes, can result in an accident. Even though the rear-quarter blind spot can be eliminated, and should be checked by all drivers, many drivers do not do so, so it is wise to avoid driving inside another vehicle's blind spot.
Effect of vehicle type
Generally speaking, larger vehicles have larger rear blind spots. For example, the blind spot behind a typical sedan could only hide a small animal, while the blind spot of an SUV can hide small children, resulting in as many as 50 children being killed by reversing SUVs each year [1]. The blind spot behind tractor trailers can contain entire vehicles, which is one reason many trucks carry warnings not to follow too close, such as "if you can't see my mirrors, I can't see you." This is partly because the driver's position is higher in a tractor-trailer.
Larger vehicles also have much larger front and side blind spots. Tractor-trailers have not only large rear quarter blind spots, but also a large blind spot directly to their left and to their front-right.