White Lines and What They Mean

Q: What are the rules on crossing white lines? Solid white lines, double white lines, white lines on the shoulder of the road; some of you have been wondering about when it’s okay to make lane changes across white lines.

A: Let’s start with where white lines are found and the types of white lines you might encounter while driving. White lines are used to separate lanes traveling in the same direction or to mark the shoulder of the roadway. They can be broken, dashed, solid or solid double and each type has a reason and some rules.

Broken: These are the lines you see separating two or more lanes going in the same direction in areas where it is reasonably safe to change lanes.

Dashed: Similar to broken lines, but with shorter segments, dashed lines are used to indicate that a lane will be ending or changing use. Exit-only lanes are marked with dashed lines, as are transition areas when a lane switches from general use to carpool.

Solid: Besides being used to mark the edge of the roadway where the shoulder begins, solid white lines are used in areas where lane changes are discouraged. Notice that it’s not prohibited; just discouraged. Lane changes in these areas present a greater risk than usual; the Washington driver guide recommends that you stay in your lane unless a special situation requires a change. You’ll find solid lines leading up to intersections, at the end of gore areas* and separating general use lanes from carpool lanes.

Solid Double: Similar to double yellow lines that indicate it is illegal to pass, double white lines indicate that it is illegal to change lanes. Solid double white lines may be close together or may be separated by eighteen or more inches of space. You’ll find double white lines at gore areas where they start wide and come to a point. Sometimes carpool or toll lanes are separated by double white lines. Even if a carpool or toll lane has limited hours where it is in effect, the double solid lines still mean “do not cross” all the time. The closest example I can think of is between Lynnwood and Bellevue on the I-405 toll lanes. I noticed that in some sections on I-405 there are double-double white lines (a pair of white lines about two feet away from another pair of white lines), suggesting that DOT must be really serious about not changing lanes.

Where do you find the law specifying the rules about the types of white lines? That’s actually a little tricky. You won’t find it in the Revised Code of Washington, and it’s only referenced indirectly in the Washington Administrative Code. Instead, the rules for white lines are found in the Manual on Uniform Traffic Control Devices (MUTCD), a national standard that engineers refer to when designing roads. The Washington secretary of transportation adopted the MUTCD, so those rules become our rules. Adopting a national standard makes a lot of sense; imagine the chaos if each state developed their own standard for road signs and pavement markings.

We’ve determined that crossing a solid white line, though discouraged, is legal. However, that doesn’t mean it’s okay to drive on the shoulder of the road. That’s covered by another law requiring drivers to keep all their wheels on the roadway unless pulling over to stop. (The shoulder is not considered part of the roadway).

It seems obvious, but I’ll mention that driving on a stretch of road where it is legal to make a lane change does not mean that a driver is entitled to make that lane change. Lane-changing drivers need to yield the right-of-way to other motorists already in the lane. And use a turn signal. I can’t tell you how many readers are cheering right now. If you’re not currently a turn-signal user, start today. It’s that little lever on the left side of your steering wheel. Just push it up when you want to turn right and down for left. That’s all it takes.


*The gore area is the triangular space between an onramp and the freeway that tapers to a narrow point. I thought that the gore area was named because of what you’d encounter if you ignored the double white lines and merged onto the freeway too soon. Actually, gore comes from an Old English word for spear and refers to a triangular piece of land (it’s pointy like a spear).


One Comment

  1. Thanks for explaining these line differences. I see these on the road all the time and have a general knowledge of what each mean, but I want to learn a little bit more about them. I’m glad that you mentioned that double solid lines always mean “do not cross”, even in a lane with limited effect hours. Now I feel like I can be a little bit more safe when I’m driving.

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