In New York City, a two-section (red and green) traffic signal was commonly suspended from a mast-arm set-up, in which is well known as the "wheelie." In the 1950s and 1960s, when signal equipment was modernized, a practice, in which was generally uncommon, was to upgrade a signalized intersection that had only one suspended traffic signal in service. The new and improved set-up used a Marbelite traffic signal cluster along with a newly installed mast-arm/guy wire set-up, in which suspended the entire cluster at the intersection. Additional heads were never installed. Below, are two pictures of a good example of an intersection that once used each set-up. At Liberty Av. and Georgia Av. Brooklyn, New York.
Original set-up. Unknown date at this time.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi1013.photobucket.com%2Falbums%2Faf258%2FSteven197981%2FPielsSign1947_zps2a228c43.jpg&hash=602a3c0309e60dc63a0ba2b3e95a40d502400671)
Altered set-up. A slightly different view of the intersection. Viewed from Georgia Av. Early 1970s.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi1013.photobucket.com%2Falbums%2Faf258%2FSteven197981%2F1526453_354349828039307_1406803399_n_zps7a635e76.jpg&hash=42b283d898f6e86d4d27da073871f7e17c5c39af)