During my online chat Monday, a traveler played a Dr. Gridlock version of the NPR Car Guys’ Stump the Chumps.

Upper River Road: “Do you have any information on the work that is being done to the center lines on River Road north of Falls Road? It looks like they’re being changed — increased height and striated lines added to them — to prevent passing or at least to discourage it. Any idea what’s going on?”

In responding, I thought it best to take the direct approach: “Nope. None at all.”

Now, I’d like to thank David Buck, a spokesman for the Maryland State Highway Administration, and the maintenance personnel at the highway administration’s Gaithersburg shop for their help on this puzzler.

Staffers went out and took a look at the site in Potomac. They saw a utility crew working along River Road north of Falls Road, but the crew was not in the roadway.

Buck said the only thing they could figure was that the question referred to work in the center of the roadway that as done about a year ago. Around that time, highway workers did add rumble strips along River Road’s center line north of Falls Road.

Many drivers will be familiar with that style of warning marks; they look like machine-made gouges along the solid double yellow line in the middle of the pavement.

About a mile-and-a-half farther north along River Road, there is a passing zone between Piney Meetinghouse Road and Swaims Lock Road, but those markers have been there for quite a long time, Buck said.

So Buck and the staff at the Gaithersburg maintenance shop suspect the questioner was referring to those center line rumble strips.

I don’t have a way of responding directly to chat questioners — it’s not like e-mail — but you can write to me at drgridlock@washpost.com.

The State Highway Administration maintains and improves roads in Maryland that have numbers. River Road, for example, is MD 190. The highway administration divides its teams into maintenance districts. The Gaithersburg shop is part of District 3, responsible for Montgomery and Prince George’s counties.