View Mobile Site
Text Size: Smaller Larger Normal

Cop Corner

POSTED February 9, 2010 4:11 p.m.

The loquacious Mark Twain once wrote, “If you don’t like the weather, wait five minutes and it will change.” After several dry years we’re finally getting some much needed rain. This is great for our area reservoirs and farms but not so great for our area roads.

I’d like to stress two safety tips for driving in wet weather, be it rain, snow or even fog. Slow down and put some extra space between you and the car ahead of you. Stopping distances increase dramatically for a vehicle on a wet or slippery surface.

Thousands of cars and trucks pass over our roads every day. Some of them leak fluids such as engine oil, coolant, hydraulic fluid and gas or diesel fuel. When the roads are dry these fluids are absorbed into the roadway surface and generally don’t cause a problem in small amounts. However, when the weather adds moisture, in the form of fog, rain or snow, to the road, it causes these slippery fluids to rise to the surface and sit on top of whatever moisture Mother Nature has deposited on the road.

Almost everyone has seen the results of someone driving too fast or following too close behind another car in wet weather. A rear end collision. The following is an excerpt from the California DMV Driver’s Handbook regarding stopping distances.

There are three things that add up to total stopping distance: Perception Distance + Reaction Distance + Braking Distance = Total Stopping Distance.

Perception distance. This is the distance your vehicle moves from the time your eyes see a hazard until your brain knows it. The perception time for an alert driver is about 3/4 second. At 55 mph you travel 60 feet in 3/4 second.

Reaction distance. The distance traveled from the time your brain tells your foot to move from the accelerator until your foot is actually pushing the brake pedal. The average driver has a reaction time of 3/4 second. This accounts for an additional 60 feet traveled at 55 mph.

Braking distance. The distance it takes to stop once the brakes are put on. At 55 mph on dry pavement with good brakes, it can take a heavy vehicle about 170 feet to stop. (About 4 3/4 seconds.)

Total stopping distance. At 55 mph it will take about 6 seconds to stop and your vehicle will travel about the distance of a football field (60 + 60 + 170 = 290 feet).

You cannot steer or brake a vehicle unless you have traction. These are some of the road conditions which reduce traction and call for lower speeds:

Slippery Surfaces.Your browser may not support display of this image. It will take longer to stop and it will be harder to turn without skidding when the road is slippery. You must drive slower to be able to stop in the same distance as on a dry road. Wet roads can double the stopping distance. Reduce speed by about one third (i.e., slow from 55 mph to about 35 mph) on a wet road. On packed snow, reduce speed by half, or more. If the surface is icy, reduce speed to a crawl and stop driving as soon as you can safely do so to install chains, if necessary.

Here are some examples of slippery roads:

Black ice. Black ice is a thin layer that is so clear you can see the road underneath it. It makes the road look wet. Any time the temperature is below freezing and the road looks wet, watch out for black ice.

Just after rain begins. Right after it starts to rain, the water mixes with oil left on the road by vehicles. This makes the road very slippery. If it continues, it will wash the oil away.

Hydroplaning. In some weather, water or slush collects on the road. When this happens, your vehicle can hydroplane. It is like water skiing; the tires lose their contact with the road and have little or no traction. You may not be able to steer or brake. It does not take a lot of water to cause hydroplaning. Hydroplaning can occur at speeds as low as 30 mph if there is a lot of water. It is more likely to occur if tire pressure is low or the tread is worn. (The grooves in a tire carry away the water; if they aren’t deep, they don’t work well.) Be especially careful driving through puddles. Puddles are often deep enough to cause hydroplaning.

There are a few laws that apply specifically to driving in wet weather. 22350 VC states that no person shall drive a vehicle upon a highway at a speed greater than is reasonable or prudent having due regard for weather, visibility, the traffic on, and the surface and width of, the highway, and in no event at a speed which endangers the safety of persons or property.

Vehicle Code section 21703 says the driver of a motor vehicle shall not follow another vehicle more closely than is reasonable and prudent, having due regard for the speed of such vehicle and the traffic upon, and the condition of, the roadway.

Lastly, 22400(a)(2) VC says in part that a vehicle’s headlights shall be operated during darkness, or inclement weather, or both.

(b) As used in paragraph (2) of subdivision (a), “inclement weather” is a weather condition that is either of the following:

(1) A condition that prevents a driver of a motor vehicle from clearly discerning a person or another motor vehicle on the highway from a distance of 1,000 feet.

(2) A condition requiring the windshield wipers to be in continuous use due to rain, mist, snow, fog, or other precipitation or atmospheric moisture.

A lot more rain is predicted for the near future so keeping these laws in mind will help keep you, and those around you, safe on those wet roads.


Cop Corner is a monthly column provided by officers of the Oakdale Police Department, offering a variety of information and safety tips.

Commenting is not available.

Commenting not available.

Please wait ...