Dear Dr. Gridlock:

As someone who goes from Alexandria to Tysons Corner in the morning rush, I have become accustomed to drivers using the two left-side lanes to try to pass as much of the traffic as they can and then diving back in before the 495 Express Lanes begin.

The morning of May 15, Capital Beltway traffic was such that two drivers were not able to find their way back in and had come to a complete stop in what was about to become the right side of the two express lanes.

This is on a curve, and it was only good fortune that kept these two from being plowed into by someone entering the express lanes at speed. Is it stupidity or madness putting oneself in such a position?

Also, although we know there is a posted speed limit, the default speed on the Beltway is 65. The default speed on the express lanes is 70 to 75, with some drivers slaloming through at even faster speeds. With the unusual left entrances and exits, this is not going to end well.

Robert Sams, Alexandria

DG: When the express lanes opened, in mid-November, some drivers managed to stray into the two new lanes on the left about a mile and a half west of the Springfield interchange that lead into the toll part of the highway. I thought that was a little weird, given all the overhead signs and warnings they had to pass to make this mistake, but the awful part was that some were stopping and backing up rather than just continuing on to the first exit and paying a small toll.

We seem to be past that phase now. Sams is describing a driving trick born more from familiarity than uncertainty. He is seeing drivers using a lightly traveled ramp to bypass traffic in the regular lanes that isn’t moving fast enough for them.

This ramp happens to be on the left side of the Beltway, but the tactic is common. Farther north, drivers see this on the Beltway’s congested inner loop through Bethesda, where queue-jumpers pull into the Wisconsin Avenue exit ramp, then bull their way back into the regular lane just before the ramp ends.

It’s dangerous in Bethesda, but it’s likely to be even more dangerous in Springfield, where drivers are going to be moving at high speed as they approach the uncongested express lanes.

Speaking of speed, the Virginia Department of Transportation is considering an official increase in the express lanes’ speed limit, from 55 to 65 mph. As Maryland did with the Intercounty Connector — where the speed limit was recently raised from 55 to 60 mph — Virginia has been waiting to gain some experience with the new lanes before making any change.

For the express lanes, a sign that reads “65 mph” might be good advertising when viewed from the more crowded regular lanes, but it would have little practical effect. As Sams notes, there’s no one traveling under 65 mph in the express lanes now unless he absolutely has to because there’s a state police cruiser nearby.

Blocking the box

Last week, I wrote about the interesting traffic dynamics in the evening rush at an intersection in the middle of the District where drivers routinely make up their own rules rather than following the lane markings.

Dear Dr. Gridlock:

I get a firsthand look at the chaos every day. I think the biggest issue for that whole intersection actually is at 12th and L streets, a very short block south of 12th and Massachusetts. The light on northbound 12th at Massachusetts turns red before the one at 12th and L, and drivers constantly go into the intersection and block the box at L Street. L Street often comes to a standstill as a result, and it sometimes take me three or four lights to turn off L onto 12th.

This intersection has only a traffic officer, as far as I know. It’s an intersection that desperately needs more or, at the least, a re-timing of the lights.

Also, once 6:30 p.m. hits, the officer leaves. Usually, traffic in the area is still horrendous.

Jonathan Fusfield, the District

DG: This zone between Thomas Circle and Mount Vernon Square has one of the more complicated traffic patterns in the central city because of the angle at which Massachusetts Avenue slices through the grid pattern.

When I responded to the letter from R. Miller of Hyattsville, I stuck to the scene right at Massachusetts and 12th, which is most unusual. Fusfield experiences the approaches to that intersection, which have their own issues.

Coordinating the signals in a tight zone where streets go south-north, east-west and northwest-southeast is difficult. I think the burden is on the northbound drivers on 12th Street who block the box with L Street and delay drivers such as Fusfield.

There also are many pedestrians in this area who must work their way around vehicles squatting on crosswalks. This is an ideal spot for the city to spread around a few more traffic control officers.