Free Traffic by Tom Vanderbilt Page A

looking in the rearview mirror. Then we could make “downward comparisons,” as with the poor saps in the Hong Kong post office, and not feel so bad. But we would also quite likely collide with the vehicle in front of us, and then cars in the next lane really would be going faster. The very nature of driving, posited as a constant progress along an endless queue, defeats us. Traffic messes with our heads in a strangely paradoxical way: We act too human, we do not act human enough.
Postscript: And Now, the Secrets of Late Merging Revealed
    People are afraid to merge on freeways in Los Angeles.
    —Bret Easton Ellis,
Less Than Zero

    We humans have achieved great things. We have unlocked the once-unfathomable human genetic sequence, sent space probes to the far reaches of the solar system, and even managed to freeze a beam of light. But there’s one scientific conquest that has largely eluded us. It’s all the more puzzling because, on the face of it, it seems so mundane: We have not found a way to make drivers merge with the most efficiency and safety on the highway.
    The situation described in the Prologue that I encountered on the Jersey highway is known in the traffic-engineering world as a “work-zone merge.” Work zones, it turns out, are among the most complex and dangerous areas on the highway. Despite the signs often warning of large penalties for striking a worker (or pleas like SLOW DOWN, MY DADDY WORKS HERE ), they are much more dangerous for the drivers passing through them than for the workers—some 85 percent of people killed in work zones are drivers or passengers. The reasons are not difficult to imagine. Drivers moving from an incredibly fast, free-flowing environment are suddenly being asked, sometimes unexpectedly, to come to a crawl or even a full stop, perhaps change lanes, and pass through a narrow, constricted space filled with workers, heavy machinery, and other objects of visual fascination.
    And then there’s the inevitable point at which two lanes of traffic will be forced to become one (or three to become two, etc.), when the early mergers, the late mergers, and everyone in between are suddenly introduced to one another. This can get sticky. It seems that even though (or maybe because) we’re all tossed together on the road, drivers are not all that comfortable with interacting; a survey undertaken by the Texas Transportation Institute found that the single most common cause of stress on the highway was “merging difficulties.”
    Traffic engineers have spent a lot of time and money studying this problem, but it is not as simple as you might think. The “conventional merge” site, the sort I experienced on the highway in New Jersey, works reasonably well when traffic is light. Drivers are warned in advance to move into the correct lane, and they do so at a comfortable distance and speed, without a “conflict” with a driver in the other lane. But the very nature of a work zone means that traffic is often
not
light. A highway going from two lanes to one, or experiencing a “lane drop,” loses at least half of its capacity to process cars—even more if drivers are slowing to see what is going on in the work zone itself. Because the capacity is quickly exceeded by the arriving cars, a “queue” soon forms. The queue, inevitably, is longer in the lane that will remain open, probably because signs have told drivers to move there.
    This causes more problems. As the queue grows, it may move far back up the highway—engineers call this “upstream”—perhaps even past the signs warning of the lane closure. This means that newly arriving drivers will be encountering an unexpected queue of cars. Seeing no reason for it, they will be unaware that they’re in a lane that is due to close. Once they learn this, they will have to “force” their way into the queued line, whose drivers may view the new arrivals, fairly or not, as “cheaters.” As the entering drivers slow or even stop to