How exactly is the speed limit enforced by aircraft, as those occasional signs along the interstates warn us?
Vic Cricchi, Fairfax
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Answer Man has seen these signs and he has thought, as you no doubt have yourself, of the extreme ways the speed limit could be enforced from above.
He doesn't think it would be sporting to use an F-22 Raptor equipped with those "fire and forget" missiles, the sort a pilot can launch from miles away. Better to come in low and slow in an A-10 Warthog and unload from the nose-mounted 30mm cannon. A scofflaw in a Chrysler Pacifica doing 76 in a 65 mph zone? A few thousand rounds of depleted uranium should teach him a lesson.
Alas, this is not what happens. Rather, the whole thing is more like a word problem from a sixth-grade math class: If two trains leave Chicago at 1 p.m., and one is traveling at 30 mph and the other is going 50 mph, at what time will they arrive in Minot, N.D.?
The secret of airborne traffic enforcement is a little device called the VASCAR. No, not NASCAR. VASCAR.
VASCAR stands for "Visual Average Speed Computer And Recorder." It's a box about the size of a clock radio. You can mount it in a patrol car or inside an airplane. Heck, you could mount it on the side of a Fire Magic Regal II gas grill, though why you would want to do that, we couldn't say.
VASCAR, said Lt. Nick Saunders of the Virginia State Police aviation unit, "is just a fancy stopwatch."
It's a fancy stopwatch that can estimate the speed of a vehicle by performing a quick time-distance calculation. Here's what happens: A light airplane circles above the interstate at an altitude of about 2,000 feet. Inside are a pilot and a state trooper who is a certified VASCAR operator. Below, painted from shoulder to shoulder at regular intervals on the highway, are wide, white lines. To check if someone is speeding, the trooper pushes a button on the VASCAR unit when a vehicle crosses the first white line, then hits the button again when it reaches the second line. The unit then displays the vehicle's speed. Both Maryland and Virginia use the system.
"Compared to radar, [VASCAR] is actually a more fair system to the motorist," said Lt. Saunders. While radar gives an instantaneous reading -- how fast you're going the exact moment you're hit by the invisible beam -- VASCAR gives you the average speed. You might get a bit of credit for decelerating, he said.
Virginia didn't write many airborne speeding citations last year, only 110. Answer Man told Lt. Saunders that didn't sound like very many for all the work involved.
"I can say with some assurance that that type of enforcement activity is going to pick up this year," he said.
You've been warned.
Traveling the United States, I've noticed that in some areas there are highway signs stating "Eisenhower Interstate System." I have not seen these signs on all the highways. What qualifies a highway for this designation?
Lonnie Rorie, Annapolis
A little history: In 1919, Lt. Col. Dwight D. Eisenhower was part of the Army's first cross-country road trip. It took 62 days for a caravan of 81 military vehicles to drive from Washington to San Francisco over rutted roads, crumbling bridges and trackless wilderness.
Twenty-five years later, Gen. Eisenhower noticed how quickly troops could move over Germany's smooth, open autobahns. His verdict: The United States needed well-built multilane highways for commerce and defense.
He was finally able to do something about it when he was president, pushing the 1956 legislation that funded our modern network of high-speed roads.
The legislation called for major population centers to be linked by more than 40,000 miles of highway. To be considered interstates, the roads had to include a minimum of four 12-foot-wide travel lanes, a shoulder width of at least 10 feet and "full control of access" -- meaning no stoplights, stop signs or pedestrian crossings.
In 1973, Sen. Charles McC. Mathias Jr. of Maryland wanted to honor the 1919 convoy. Rather than put up signs that read "Transcontinental Motor Convoy of 1919" -- the official name -- Congress mandated signs reading "Dwight D. Eisenhower Highway." The signs were to be placed on a combination of highways roughly approximating the original route. That included Interstate 270 between the Capital Beltway and Frederick.
It never caught on, though, and it wasn't until 1990 that the National System of Interstate and Defense Highways officially became the Dwight D. Eisenhower System of Interstate and Defense Highways.
Any highway that is an interstate can display an "Eisenhower Highway System" sign, which has five stars in a circle, symbolizing Ike's status as a five-star general. There is no federal regulation mandating where the signs be placed. It's up to each state highway department, which is why sometimes you see them and sometimes you don't.
The next time you are able to bypass some Podunk town by taking an interstate to the beach, thank Dwight Eisenhower. And those backups on I-95, I-66, I-270? Not his fault.
My assistant, Julia Feldmeier, helped research this column. E-mail email@example.com. Or write John Kelly, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071.