Why You Shouldn’t Drive Through a Flooded Road

Q: I noticed Whatcom County Public Works added a note to a recent road closure notice, reminding people not to drive past those temporary closure signs for flooded streets. Sometimes the county has put so many out that it takes a while to pick them back up. Drivers see the road doesn’t have much or any water over it, so they ignore the sign and go past it. Is it illegal to ignore those temporary signs?

A: This time of year it’s not uncommon to encounter flooded roads, so it’s a good idea to review the rules about road closures due to flooding. Since the signs that notify drivers of flooding follow the same guidelines as other road closure and warning signs, this will be more a review about traffic signs (in the context of flooding.)

There are a lot of different kinds of road signs; some tell us the rules, some give cautions, some provide information. Each sign conforms to a standard that is specified in the Manual of Uniform Traffic Control Devices (MUTCD). The MUTCD is nearly 900 pages long, and is entirely focused on signs, road markings, and traffic signals, making it useful not only for designing roadways, but also as a cure for insomnia. Or if you don’t like your traffic information to be mildly humorous (emphasis on mildly), read the MUTCD instead of these articles. I promise, there are no jokes in the MUTCD.

Back to the signs. The color of a sign is an indicator of its function. There are actually thirteen colors identified in the MUTCD for communicating traffic information. We’ll focus on three: white, orange, and yellow. A white sign is a regulation sign, meaning that it communicates rules. Speed limit, no passing, and yes, road closure signs are all white. Driving around a white “road closed” sign is a violation of the law.

Yellow signs are warning signs. They let you know of changes in the driving conditions that require additional caution. It could be for many different things; an upcoming curve, a dead end road, or water over the roadway. Driving past a yellow “water over roadway” sign isn’t illegal, but it is a good indicator that there is additional risk up ahead.

Orange signs are for temporary traffic control. They could be regulatory, like a slower speed limit in an area with water over the roadway, or informational, like giving the direction for a detour in the case of a closed flooded road. During flooding you might find orange signs along with either yellow caution signs or white “road closed” signs.

That covers the rules about signs, but what’s the big deal about driving through a closed flooded road? According to the flood experts, with six inches of water on the road most vehicles will no longer have traction. Twelve inches of moving water will sweep a car off the road (and during a flood water often moves over roadways), and 24 inches will cause nearly any other vehicle to drift. Unless a vehicle is designed for off-roading through mud and water, it’ll take a lot less than that to cause it to stall. If you do end up stalled in a flooded road and decide to walk home, it only takes about six inches of moving water to knock a person off their feet.

Even if there are only a few inches of water over the road, it’s hard to know how much is flowing under the road. Erosion happens fast during a flood, and entire sections of the road can fall away in seconds, along with anyone driving on it. If you take a look at flood-related fatalities, you’ll find that most deaths involve driving. In fact, vehicle-related drowning during a flood is more common than any other weather-related death.

One more thing: There’s a theory out there (and I haven’t found data to either confirm or deny it) that drivers who blatantly disregard traffic laws (as opposed to errors of ignorance or inattention) are more likely to be involved in other criminal activity. That correlation might incline law enforcement officers to focus on watching for “road closed” violators. For anyone reading this that has an outstanding warrant for their arrest, driving through a closed flooded road includes all the above risks, along with the potential for a new temporary housing situation. Stay safe and drive wise.


Leave a Reply

Your email address will not be published. Required fields are marked *