To Use or Not to Use Cruise Control in the Rain

Should speed or cruise control be used on wet roads. Curiously, we have seen this question answered more anecdotally than directly by the automotive community. Its frankly a safety issue, and thus deserves more attention than it has received.

So first, the answer is no, do NOT use speed control on wet roads. Now we’ll dig a little deeper.

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Another Cruise Control IndicatorIts important too start with an  acknowledgement that your owner’s manual will actually state that cruise control should not be used in slippery conditions. These warnings are buried deep in the manuals that few will ever read. A driver already familiar with cruise control would not likely have a need to refer to the manual at
all.

The statements are also quite soft, and have the feel of covering one’s back side rather than a full on and believable warning. Mercedes-Benz includes the most useful explanation. “Rapid changes in tire traction can result in wheel spin and loss of control.”

This speaks nicely to the basic problem, which is that hitting a puddle or standing water with the cruise control on can cause the tires to spin faster, if only for a moment. The result then is likely hydroplaning. The natural driver’s instinct to brake at that moment would disengage the cruise control, but can exacerbate the slipping. All of which might have been avoided with the cruise control been left off.

Drivers who have lost control in wet conditions using cruise control report their vehicles accelerated when control was lost. This really isn’t not possible, and likely an illusion or impression created by the loss of traction. Slipping wheels would result in the engine revving higher, which, coupled with the loss of traction, could easily feel like acceleration.

NHTSAWe searched the National Highway Traffic Safety Administration (NHTSA) and were surprised to find nothing. Consumer Reports, in a single paragraph, makes mentions turning cruise control off in one article about driving in downpours, but says nothing else anywhere.

Something called the National Safety Commission, which we’ve never heard of, had more to say on the subject, also concluding that cruise control should be off. We also found a reference to truckers being taught to leave cruise control off in wet conditions.

The only information found from an official, that is government, site comes from the state of Maine, linked here, and their message is leave it off. Lots of experience with slippery roads in north country.

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Active Cruise Control SymbolTo be sure, the advanced nature of today’s vehicles begins to blur the lines. Stability control could, and we emphasize could, compensate for loss of traction. However, we have simply been unable to find any definitive research one way or the other. The move towards autonomous vehicles certainly suggests that
all weather conditions will have to be accounted for, but testing in adverse weather is only beginning.

For the time being, we conclude that it is best to play it safe and keep cruise control off if the roads you are travelling are not perfectly dry.

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