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Over the past couple of days, we've been talking with Robert Snowden, a researcher at the University of Wales. He has done some research that shows that when you're driving in fog, chances are you're driving faster than you think you are.

Hi, I'm Dave Thurlow and this is The Weather Notebook. It turns out that fog can actually create a visual illusion. Fog reduces the contrast between things we see and that makes us feel like we're going slower than we are. But is there anything that can be done to help drivers know how fast they're really going when they're driving in low visibility? Here's more of my conversation with Professor Snowden:

Robert: "The obvious thing would be look down at your speedometer because that gives you the right answer. But, unfortunately we know that people are very reluctant to do this when it's foggy. People are too busy paying attention to what's going to emerge out of the fog at them."

So the researchers are looking at other ways of letting the drivers know if they're going too fast.

Robert: "One possibility might be a speaking speedometer, if people would be willing to tolerate such an annoyance in a car. The second would be to perhaps use what we call head up displays, where the information about speed or indeed anything else can be pasted onto the windscreen, directly in front of the view of the driver. But perhaps the major thing we can do is to educate people that this does occur. Do have a quick look down at your speedometer to check that you are going as slow as you think you are."

For more information on our special series of fog and perception visit our website at mountwashington.org/notebook. The Weather Notebook is underwritten by Subaru the beauty of all wheel drive with major support provided by the National Science Foundation.