Summer sun, shining right in the face, tires our eyesight and reduces the focus and visibility. When the sun is low in the sky (usually at evening, morning time and during the winter), the light falls almost parallel to the road, the stress on the eyes is greatly increased. Road shines strongly, reflecting the rays of the sun, and on this contrast the vehicles seem black. Silhouettes of people are lost on the road, as the apples of our eyes are contracted, limiting the amount of light going through the eye. As a result there is the visibility deterioration of objects in the shadow.
Driving into the low sun, both in its full light and the dark areas requires a heightened attention. In addition, when driving into the sun, traffic light colors, brakelights, direction posts are paled notedly. When the sun shines behind it is even more difficult to distinguish the traffic signals, and all taillights of a car glare by reflected light of the sun and it is hard to define which light is illuminate, and which isn't. In this case you need to drive in the way the shadow from your car falls to the vehicle ahead. In this manner it will be easier for you to watch its taillights. The low sun, glaring at side car glass more acceptable for the driver, but also may cause some troubles, making contrasts of the shadows on the roadway. In all these cases you need to use the sun visor, reinstating visibility of the road. However, it is not recommended to use sunglasses because they limit the brightness of the road bits and at the same time reduce the visibility of places and objects in the shadows.