Quite a bit especially if your tires are worn down to or below the tread depth limit.
Wet roads do reduce traction, which can negatively impact vehicle handling and stability. When tires encounter water, the risk of hydroplaning increases, leading to diminished contact with the road surface. While wet conditions can also affect braking distance, the degree of impact depends on various factors such as tire type, tread depth, and water depth. Overall, both traction and braking are compromised on wet roads.
Dry asphalt roads
Spreading sand over icy roads provides traction for vehicles by increasing friction between the tires and the road surface. This helps to reduce the likelihood of slipping and skidding, improving overall safety for drivers.
by improving tire traction for one
It notifies the driver that the road conditions are creating reduced friction between the tyres and road surface, hence, reduced traction. You'll see it on particularly wet roads, snow/ice covered roads, etc.
Salt is used to melt ice by lowering the freezing point of water, making it easier to remove. Sand is used for traction on icy roads to improve tire grip and reduce the risk of slipping. Together, they help improve road safety during icy and snowy conditions.
Salt or a mixture of salt and sand is typically placed on roads when it snows to melt the ice and improve traction for vehicles. Sand alone can also be used to increase traction on icy roads.
Asphalt roads are considered to provide the best traction for automobiles in most conditions. Concrete roads will provide better traction in high temperature areas.
I believe what you are asking is why they salt and/or sand roads. The answer to this, is when it snows, rains, sleets or hails badly, the road becomes slick, so the salt/sand is meant to make it a bit rougher, so the cars don't skid.
This helps with the traction of the tires to the road. It helps the tires not slip or slide on the ice.
Roads have a rough surface to provide traction for vehicles, especially during wet conditions. The texture helps to prevent vehicles from skidding and provides better grip for braking and turning. Additionally, the rough surface helps to reduce noise and improve visibility of road markings.
The water creates a layer between your tires and the road so your tires don't grip the road, they lose traction.