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Ever since the first slopeline system was installed in 1949, both airline managements and the Air Line Pilots' Association have protested against it. Their basic objection is that any system with two lines of lights can look like an outlined runway in difficult weather. They prefer a single "centerline" of lights leading to the center of the runway.
Balls of Fire. The best system of all, according to many pilots, is the one at Newark Airport. Instead of two lines of lights, it has a single centerline of horizontal bars, which cannot possibly be mistaken for the runway. In thick weather stroboscopic lights ("balls of fire") flash briefly in sequence so that they look to the pilot like a stream of tracer bullets.
The CAA recognizes the failings of the slopeline system, and the centerline system is now its standard for civil airports. But, presumably because of lack of money, only eight U.S. airports have centerline lights. Only Newark has the balls of fire. A hopeful rumor at International Airport is that the slopeline lights of Runway 4 (now out of commission) will be replaced by the centerline system, perhaps including the balls of fire.
* For another view of the tragedy, see JUDGMENTS & PROPHECIES.