The Marshalite Was An Alternative Traffic Signal That Displayed?
Answer: Signal Wait Time
Waiting at an intersection beneath a seemingly unending red light is a certain sort of agony, an agony that none of us would have to endure if the invention of Australian engineer Charles Marshall had taken off.
In 1936, Marshall invented the Marshalite, a rotary traffic signal that displayed the amount of time remaining for a given signal color via its clock-like face. While you waited for the light, you could watch the hand sweep across the face of the Marshalite display to see how close the light was to changing. The rotary signal was always used in conjunction with traditional traffic lights.
The Marshalite signals were used in several cities across Australia during the mid 20th century (and a similar and independently designed signal was used in parts of Europe at the same time), but the design never gained widespread adoption and by the 1970s, changing traffic laws and lack of interest in the installation of new units led to the removal of the alternative signals.
Image courtesy of Dysprosia.