When NOT to RV with your cruise control

photo: markdoliner on flickr.com by permission

Everyone's heard the story of the man driving his motorhome down that long, lonesome highway. Feeling the pull of a "call of nature," the story goes, he sets the cruise control, climbs out from behind the wheel, and heads off for the bathroom.

It's a delightfully silly tale, but one that does have a bit of moral to it. Besides, "don’t drink too much coffee before you hit the road," there's the corollary: There are times when you should not use cruise control.

One of those times may not be what you think: In the rain.

No, we are not spreading some kind of goofball Internet rumor here. Really. When the rain comes down, so should your speed control. Here's the why's and wherefores.

First there's what they call "Florida Ice." Picture yourself cruising along the Interstate, almost lulled by the days of fine weather you've been enjoying. But then, here comes that killjoy rainstorm that blows through, wetting up the roadway for the first time in maybe months. During those months of fine weather, the roadway has been accumulating a fine layer of oil and grease from passing motorists. The rain hits that layer, the layer lifts, and you have instant slip and slide setup. We'll come to the business of cruise control in a second.

Because here's the second rain scenario, the heavy rainfall. If you've driven in the Desert Southwest during the hot summer season, you've probably met up with our pal, monsoon rain. This isn't just a nice, put a little damp on, this is a full-fledged gully-washing gusher that not only makes visibility drop in a hurry, it also puts a thick layer of water on the roadway.

Now in either scenario, oil mixed with water, or just plain old, "too much water," comes the driving scare called hydroplaning. With too much water, your tires simply can't squeeze the water out of the treads quickly enough. With oil mixed with water, the friction coefficient that makes the tires grip the road flies out the window. In any case, the result is an easy loss-of-control where your rig can start spinning out and heading in directions you DO NOT want to go – like for the ditch, or worse, for that loaded gasoline tanker.

Dealing with a spin out or hydroplaning means backing off the gas, staying off the brake, turning into the skid, praying hard, and maybe changing your undergarments when the danger is past. BUT if the cruise control is switched on and your rig hits one of these perilous conditions, it ain't smart enough to know the expression, "Back off the gas!" Cruise control wants you to maintain that set speed, come hades or high water, and in the case of hydroplaning, you've already got the high water.

How do you shut off the cruise control? The immediate reaction is to hit the brake – which if done too hard, will only contribute to the problem. If you're smart enough to hold yourself back and hit the cruise control "off" switch, you answered correctly, but by the time you can react and hit it, you may well be mixing paint with a semi-truck. So, says the National Safety Commission, when you see the threat of rain, just shut the cruise control off until you're "in the clear."