‘Greenlight’: How a term for trains has become the go-ahead in any trade

“Fed Gives Green Light to Lowering Interest Rates," blared headlines after a recent speech by Federal Reserve Chair Jerome Powell. Other papers reported that season four of the Apple TV series “Ted Lasso“ is “Close to a Green Light." The latest Covid-19 vaccines have received a “green light" from the Food and Drug Administration.

“Green light" is also part of the colorful metaphorical language exchanged between writers and editors. It is a term that I’ve grown to appreciate over the 11 years that I’ve been writing this column, which ends this week. My weekly routine always began with a topic I proposed to my editors—“a pitch," to use a metaphor borrowed from cricket and baseball. When I got the “green light," it was full steam ahead.

Steam is actually key to understanding the roots of the “green light" metaphor, which began in the days of steam-powered locomotives. In 19th-century Britain, engineers needed a system of signals to regulate train traffic. While red lights were always a signal to stop, the “clear" signal was originally a white light, while green signified “caution." As an 1839 guide explained, “A green light should be placed at each station at the spot where the engine-man should slacken his speed."

It soon became clear, however, that white wasn’t an ideal “go" light. Engineers found that if the glass on a red or green light broke, it would appear white, making accidents more likely. So green took over as the signal to proceed, and yellow or amber was used as a signal to slow down.

With the rise of automobiles in the early 20th century, electric traffic lights with green, yellow and red lenses became a standard feature on roadways around the world. John Dos Passos’s 1925 novel “Manhattan Transfer" describes cars stopped at an intersection on a Long Island road, waiting for the signal to go: “Green light. Motors race, gears screech into first."

Within a few years, a “green light" had the power to grant permission to proceed, on roads and off. A 1930 article on minor-league baseball in the Atlanta Constitution, for instance, announced that night games were “given the green light by the league heads and most of the clubs will go ahead."

The entertainment industry quickly seized on the term as a verb, as in a 1944 wire story announcing that “four pictures have been greenlighted at Warner Bros. Hollywood studios by Jack L. Warner." Turning a noun into a verb can be appealingly snappy, but it can also raise usage quandaries. Should the past-tense form be “greenlighted" or “greenlit?" The latter appeared as early as 1962, when a Hollywood Reporter columnist wrote that “CBS greenlit 39 of George C. Scott’s new segments."

Since then, the popularity of the more efficient “greenlit" has rivaled “greenlighted," following in the footsteps of “lit," which has outpaced “lighted" as the past tense of the verb “light." A usage note from Merriam-Webster observes that “the dominance of ‘greenlit’ is likely to continue to grow," as “most writers and editors have already given it the go-ahead."

I was certainly grateful to secure this go-ahead for my own column ideas over the years, which allowed me to venture forth into some of the more colorful corners of our lexicon.