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Turn on your lights. This seems like a no-brainer, but it is certainly worth mentioning. California Vehicle Code 24400 requires California drivers to drive with headlights on after dark and in inclement weather. Even if it is raining during the day, it is very important to drive with your headlights on; even if it doesn’t help you see the road any better, it helps drivers coming the other direction spot you.
Keep your distance. It is important to reduce your speed relative to the amount of water on the roadway. In fact, with as little as 1/12 inch of water on the road, tires have to displace a gallon of water per second to keep the rubber on the road; with that in mind, it is critical to stay a safe distance away from other drivers and allow yourself plenty of time to stop. In inclement weather, it is helpful to stay a five-car length away from the vehicle in front of you (or 1 second of following distance per 10 miles per hour).
Slow it down. Drive more slowly than usual to ensure you can stop when you need to. Especially on highways or in heavy rain, slowing down will allow you more time to react to other drivers or unexpected hazards, such as falling tree branches or blowing debris.
Know your tires. The maximum speed you can drive is directly related to the tires on your vehicle. Old polyester tires do not have the traction that newer radial tires do, but even new tires can lose their grip on wet pavement as the tread wears thin.
Understand hydroplaning. “Hydroplaning” is the term for when your vehicle travels on top of the water and has little to no contact with the ground, greatly reducing your traction and ability to stop. Do not panic or make any sudden turns; instead, let off the gas and steer straight or slightly in the direction you are headed. Traveling at a reduced speed will reduce the danger of hydroplaning significantly.
Understand your brakes.
Avoid flooding. Do not drive through standing water or flowing water in a roadway unless you are able to judge the depth of the water somehow (e.g. by watching another vehicle drive through it). The depth of the water can be very hard to judge by sight alone, and flooding your engine can cause it to stall. (Plus, in deep water, the current could actually float your car away from the roadway.)
Be wary of dry spells. During a dry spell, grease and engine oil build up on the roadways. When these elements are mixed with fresh rainwater, it causes the roadway to become extremely slick. Exercise extra caution when it rains after a dry period, particularly for the first few hours of rainfall.
Avoid cruise control. Cruise control is great for dry driving conditions, but using it on wet pavement or in inclement weather can cause you to lose control of the vehicle. Driving without cruise control will allow you to control the vehicle better and make more last-minute decisions when needed.
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