Signs such as these – numbered 0 through 6 -- along Eisenhower Avenue in Alexandria help ensure taxi passengers aren’t ripped off. (John Kelly/The Washington Post)

Going west on Eisenhower Avenue in Alexandria, just after it passes over Telegraph Road, there begins of series of numbered signs. They start at 0, continue past the animal shelter and end at 6. They are not a tenth of a mile apart (we measured). They do not seem to indicate anything in particular (bus stop, utilities, etc). Eisenhower is an evacuation route, but how would the signs relate to that? Each sign is just a number, with no other information. Can you figure this out?

— Lily Engle , Alexandria

Answer Man wouldn’t be much of an answer man if he couldn’t. The signs are actually one-sixth of a mile apart, starting at a sign labeled “0” and continuing until one labeled “6.” There also is a set of signs on the south side of Eisenhower, ascending in order from west to east, just as those on the north side of Eisenhower ascend when driving east to west.

Their purpose can be discerned by consulting Section 9-12-131 of the Alexandria City Code. Allow Answer Man to quote:

“All taxicabs shall be equipped with taximeters fastened in front of the passengers, visible to them at all times day and night. . . . It shall be inspected and certified by the hack inspector at an annual cost determined by regulation for each meter, at all points and connections which, if manipulated, would affect its correct reading and recording.”

That stretch of Eisenhower Avenue is a taxi meter course, where inspectors check to make sure the city’s taxicabs have properly calibrated meters.

“The reason those signs aren’t at tenth-of-a-mile increments is because the meters are calibrated at sixth-of-a-mile increments,” said Bob Garbacz, division chief of transportation for the City of Alexandria.

Each sixth of a mile aboard a cab in Alexandria costs 36 cents, in addition to the $3 base charge, plus any special charges for waiting time, extra passengers, snow emergencies, etc.

Alexandria’s 767 taxis are inspected from March through June. The city’s two hack inspectors do a safety check in a parking lot at the intersection of Stovall Avenue and Pershing Drive. They also check that a lead seal on the taximeter has not been broken and that the machinery has not been tampered with. Then they sit in the passenger seat as the driver heads down the course, checking that the meter turns over at the proper sixth-of-a-mile increments.

Bob said it’s a good spot: straight, not too much traffic.

“Unfortunately, Eisenhower is getting much more congested,” he said. “Still, it’s the best place to go.”

I live in Columbia Heights. Throughout the neighborhood, there are several U.S. post boxes that, rather than being blue with a chute for mail, are green and have no visible opening. What are these boxes?

— Janelle Tupper , Washington

You know how when explorers trek through an icy wasteland, they often head toward pre-arranged points where critical supplies have been airdropped? Those green boxes are just like that. Well, sort of.

“They’re relay boxes,” explained George Mignosi, vice president of the National Association of Letter Carriers. “Any mail that the carrier can’t carry on their shoulder or keep in the vehicle itself gets locked in a relay box. . . . You’re more likely to find them in densely populated areas with more foot routes than routes with vehicles.”

A fully loaded mailbag weighs about 35 pounds. A letter carrier may have 80 or more pounds of mail to deliver in a day. A postal service driver fills one or more relay boxes with mail that has been presorted by address.

Some foot routes are arranged so that the carrier comes to a relay box just when his or her bag is empty. Others are arranged so that the carrier returns several times to the same central relay box.

“I would visit a relay box at least four times a day,” said George, who delivered mail in Brooklyn for 30 years.

The green boxes are less common than they once were, George said, because of the decline of first-class letters.

“But with more bulky parcels, the relay box is still a helpful tool,” he said.

Getting stoned

In March, Answer Man wrote that a million tons of granite adorn the interior of the U.S. Geological Survey building in Reston. That prompted Greg Durocher of Anchorage to write: “A million tons of stone is enough to create a solid block of rock nearly 100 yards long, 50 yards wide, as tall as a three- story building. Are you sure they said a million tons, and not a million pounds?”

Well, they did say a million tons but are having second thoughts.

“Although we don’t yet have a weight that we can provide with confidence, we believe that the tonnage is significantly less than the one-million ton figure we quoted earlier,” wrote the Survey’s Diane Noserale.

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