Glare creates visual discomfort and lowers the ability to see contrast. Glare can impair vision for all drivers, but is especially bad for older people. The poor visibility causes people to concentrate their attention directly ahead in order to see where they are going. This decreases the probability of seeing with the peripheral field, so that, for example, it would be harder to see a car or pedestrian approaching from the side. Rain also impairs vision in other ways.
Rain affects ability to see through the car windshield.
Even with windshield wipers operating, the splashing of rain and the windshield wipers themselves periodically block vision. The rain acts like a lens which scatters lights and distorts the visual scene image. The clutter and movement caused by the raindrops falling on the windshield further draw attention and masks objects on the road. Lastly, wipers only sweep part of the visual field clean of rain. Rain also affects visibility by changing the amount of light reflected from the road back to the driver's eye.