On our way to dinner the other night my wife asked me a question that I had never thought of before. Why are the new white dashed lines on Minnesota highways outlined in black? Did they mess up and have to redo the lines? Were they yellow for a construction project and got changed back to white? MnDOT posted the answer yesterday in a Tweet. 

Those black lines around the white ones are to help you see the white better on the roadway.


If you've done some driving lately, especially in the mornings when it's been really dark due to the rain, you know it's tough seeing the lines no matter the contrast. That's one of the reasons that the paint also has "glass beads that reflect light" in it.

According to MnDOT the glass beads make the lines more visible to drivers, due to the reflective nature of the glass. You can really see the difference when you've got freshly painted lines on the road.

Don't worry MnDOT knows what you are thinking, won't the glass beads just get scraped off in the winter?

"To prevent the beads from being scraped off by snowplow blades or traffic, MnDOT now recesses most markings into grooves." - MnDOT Tweet

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