Rules of the Road

How slow should you drive in construction zones if there isn’t a speed limit posted?

Question: How slow should one drive while traveling in road construction areas (marked with orange signs, cones and flags) if there isn’t a construction zone speed limit posted?

Answer: In Washington it seems like the four seasons are fall, winter, spring and road construction.

Last week I was nearly landlocked by all the construction projects happening between me and where I was trying to go. I’m not complaining; these projects needed to happen.

It’s just that when reliably dry weather only lasts for a few months, lots of road construction projects get crammed into a short amount of time. With so many road projects in the works, it’s almost inevitable that we’ll encounter them in our routine driving.

Sometimes you’ll encounter a reduced speed limit sign for a construction zone, but they’re posted less frequently than you might expect.

Based on memory (which isn’t as reliable as I like to think it is) I recall seeing quite a few construction zone speed limits in the past, but when I drove through some construction zones recently I didn’t see any reduced speed limits. That’s not because the sign people are slacking on the job; it’s actually intentional.

A few years back the Washington Department of Transportation made it a policy to design work zones that would minimize the need for speed limit reductions. While not an option in every project, wherever possible, the goal is to keep the speed limit the same during construction.

I checked with a local traffic engineer and he confirmed that it’s not WSDOT that tries to plan their work zones to be safe at the posted speed limit; local public works departments do the same on their projects.

It’s important to note, especially in construction zones, that the posted speed limit is a maximum speed, not a required speed.

Even on construction projects that don’t have a reduced speed limit, you might see a sign with an advisory speed. You’re welcome to, and actually required to, drive slower if that’s what it takes to avoid a hazard.

Posted speed limits are actually the second bullet point of the speed law.

The first section says, in part, “No person shall drive a vehicle on a highway at a speed greater than is reasonable and prudent under the conditions and having regard to the actual and potential hazards then existing.” Or put simply, drive slow enough so that you don’t risk a crash, no matter what the posted speed limit sign says.

Our brains can only process a limited amount of information at a time.

When you drive through a new or changed environment with a lot going on, such as a construction zone, choose a speed that allows you time to absorb the roadway activities; things like workers on the roadside, construction equipment crossing the roadway and other drivers that are distracted by the construction work.

The engineer I spoke with said that the most common kinds of crashes to occur in construction zones are read-end collisions. He attributed it to people who are looking at the construction work instead of the roadway.

If you’re doing that while the driver in front of you is doing the same thing, but at a slower speed, you get a rear-end crash.

His advice, when his son began to drive, was, (liberally paraphrased) “If you want to watch people work, I’ll take you to a construction site. When you’re in the car pay attention to the road.”

The right speed is the one that gets you through the work zone safely. Notice that I didn’t say the speed that gets you through without crashing.

Sometimes people avoid collisions not because they’re safe but because they get lucky, and luck is a lousy strategy for driving.

The traffic engineer had a recommendation for how fast to drive through a construction zone: Go the speed you’d feel is appropriate if your mom was on the side of the road.

I always hope that people will make safe driving decisions because they care for the well-being of themselves, their passengers and the other people on the road.

For those that need additional incentive, traffic fines in construction zones are double the regular fine, and the penalty can’t be reduced, waived or suspended.

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Doug Dahl, Target Zero Manager for the Whatcom County Traffic Safety Task Force, answers questions about road laws, safe driving habits and general police practices every Monday. Ask him a question using our form. Target Zero is Washington’s vision to reduce traffic fatalities and serious injuries to zero by 2030. For more traffic safety information visit