What is the fog line?

I had no idea what the “fog line” was until I became and a prosecutor and started handling DUI and other traffic prosecutions. It sounded mysterious. Was it really foggy?

Of course not, I learned. Just the opposite. The “fog line” refers to the bright white line painted on the edge of the roadway that separates the legally drivable portion of the road from the un-drivable portion.

When you're driving—on a two-lane highway, for instance—you have to stay between the fog line and the broken yellow line separating traffic moving in opposite directions.

And, as the Court of Appeals made clear in a December 2018 opinion, you can't cross over the fog line—even for a millisecond.

A driver can be stopped for crossing over the fog line--even for a second

In State v. Alvarez, a Washington State Patrol trooper stopped the defendant's car after her wheels traveled over the fog line by approximately one tire width. After stopping her car, he investigated and arrested Alvarez for DUI.

Alvarez challenged the stop. Yes, she admitted, she technically violated RCW 46.61.670, which makes it a traffic infraction when any of your car wheels travel off the roadway. But then she pulled out the Prado card and hoped to cash in.

In State v. Prado (an appeals court case from 2008), the Court ruled that a vehicle must be driven “as nearly as practicable” within a single lane of travel. There is no violation, therefore, for “brief, momentary, and minor deviations of lane lines.”

Crossing over the fog line once, Alvarez argued, clearly was a minor deviation under Prado and didn't justify a traffic stop.

The district court and the superior court agreed with Prado, but the Court of Appeals did not.

The Court began its analysis with a seemingly obvious question but of crucial importance to this case.  What is a roadway? A roadway (per the legislature is “the portion of the highway improved, designated, or ordinarily used for vehicular travel.”

The area outside the fog line, under this definition, is not the roadway. It doesn't matter if the area is completely paved and therefore—at least in theory—safe for travel. What matters is that drivers don't normally travel outside the fog line. And furthermore, when you're dealing with unpaved and graveled areas, this area is clearly not designed for road

By this definition, the area to the right of the fog line is not the roadway. It doesn't matter if this area is completely paved and therefore—at least in theory--safe for travel. People don't normally travel in the area to the right of the fog line and—in some roads, where this area is unpaved or graveled—it's clearly not designated for road travel.

So what about Prado opinion? Quite simply, the Court held, the wheels off roadway statute doesn't include the “as nearly as practicable” language as does the status analyzed in Prado.

RCW 46.61.670 doesn't allow for any minor deviations. As the Court put it, “there is no room for error.”