Dear Dr. Gridlock:

On most evening rush hours, there is someone directing traffic at 12th Street and Massachusetts Avenue NW. The person seems to direct traffic on Massachusetts Avenue only. It is done very well: People are stopped before they can clog the intersection, and they are even pulled over and lectured when they do block it.

On 12th Street, there are three lanes: left turn only, left turn and straight, and right turn only. I would say at least 50 to 60 percent of traffic using the right-turn-only lane goes straight, and nothing is ever said or done.

R. Miller, Hyattsville

DG: That is one weird intersection. I’ve spent a lot of time watching the traffic there. (People tend to move away from me when I say things like that, but it’s what I do.)

First, I’d like to join in complimenting the D.C. traffic control officers who work in this extremely busy intersection between Thomas Circle and Mount Vernon Square in downtown D.C. That takes patience and fortitude.

When the officer isn’t there, drivers feel free to block the intersection and straddle the crosswalks. There are intersections more infamous with rush-hour commuters, but this one is right up there with the worst. Even when the traffic officer is there, drivers don’t always obey the officer’s hand signals or the traffic light.

I agree with Miller that the lone officer spends the most time working on the Massachusetts Avenue traffic, but that’s a full-time job. Expanding the force of District Department of Transportation traffic officers might be the single best investment the city could make in easing rush-hour congestion.

But the thing that makes the intersection weird is the traffic on 12th Street, which is one-way northbound. The lane lineup is as Miller described, but there is another lane to the far right — a parking lane except at rush hour, when it’s open.

Many of the drivers are going to make a left onto Massachusetts. That works out pretty well. Others want to continue north on 12th, which will take them to Rhode Island or Vermont avenues. Some cars use the middle lane with the straight-ahead arrow to do that. Most of the straight-ahead traffic uses the lane marked with a right-turn-only arrow.

Here’s the weird part: I don’t hear anyone honking. In a town full of travelers who want everyone else to obey the traffic rules, there’s some sort of mutual understanding that this particular lane marking will be ignored.

And get this: For the most part, it works out pretty well. It’s just strange to look at.

Do you encounter any similar laissez-faire locations, where travelers appear to share an understanding that doesn’t match the official guidance?

One possible explanation for why it doesn’t appear to cause great difficulty at 12th and Mass.: There’s almost no one on 12th at this point who actually wants to make a right turn onto eastbound Massachusetts. Most of those drivers were siphoned off at a right turn a block back. The rare driver who does advance on 12th Street to make a right turn is likely to use that spare lane on the far right, the one that’s available for parking off-peak.

Still, I know from your many letters over the years that it takes very little to pit one traveler against another when one perceives a rules violation.

No break FOR Blue line

Dear Dr. Gridlock: Do you know of any plans to reduce the rush-hour fares to off-peak fares since the Blue Line riders will no longer be getting rush-hour service?

Colleen M. Coyne, Springfield

DG: Metro riders who have no realistic alternative but to take the Blue Line to certain stations got the short end of the Rush Plus service adjustments last year. This year, that end will get even shorter as Metrorail adjusts schedules once again to accommodate the arrival of the Silver Line trains heading to the District through the Rosslyn tunnel.

At that point, Blue Line trains will be scheduled to reach platforms every 12 minutes, whether at peak or off-peak. At rush hours, that will be the biggest gap between trains anywhere in the rail system. Metrobus service adjustments might help some of those Blue Line riders, but buses don’t have the capacity or speed to make a big difference.

And no, there’s no indication that Metro’s board would lower fares on the Blue Line. The 12-minute gaps are within the board’s guidelines for what constitutes rush-hour service.

It’s no comfort to those Blue Line riders, but thousands of other commuters are going to have their travel patterns changed when the Fairfax Connector and Metro reroute buses to the five new Silver Line stations in Fairfax County. Overall, the creation of the Silver Line means a huge and fairly rapid change in the Washington region’s commuting habits.