Where does the expression “green wave” come from?

The earliest use I could find in English of 'green wave', with the sense of "coordinated traffic signals", ascribes the origin of the phrase to Germany, and refers to streetcar railway operations in 1927 Chicago:

Other interesting features of the Chicago operation were the famous co-ordinated traffic signal system — we say in Germany the Green wave"…

Electric Railway Journal, January 14, 1928, p 95.

In the U.S.:

Signal Timing U.S. dept. of Transportation

Managing Traffic Flow Through Signal Timing by S. Lawrence Paulson

It's a commuter's dream: The avenue is thick with traffic, but green lights appear with regularity. Traffic flows smoothly, and lane changing is minimal. Tailgating is rare. When a red light does appear, no one tries to sneak through. Driving seems almost ... civilized.

It sounds like a miracle, but it may just be another success story resulting from traffic signal management, one of the most cost-effective ways of keeping traffic moving smoothly and making streets safer.

Traffic signal management can be defined as using improved tools, techniques, and equipment to make existing traffic signal control systems operate more efficiently.

In Am spoken English typically called traffic light synchronization. Green wave appears to be of Eu origin. I could find no expression origin.

"the term Green wave has also been applied to railroad travel. For several years starting in the 1960s, the German Federal Railway maintained an advertising campaign featuring the slogan garantiert grüne Welle (Guaranteed Green Wave), which communicated the notion of speed, limited delays and open track blocks to potential customers choosing between train and automobile travel, and was featured prominently in promotional materials ranging from posters to radio jingles."

(www.revolvy.com)

"Henry A. Barnes (December 16, 1906 – September 1968) was an American traffic engineer and commissioner who served in many cities, including Flint, Michigan; Denver, Colorado; Baltimore, Maryland; and New York City. Barnes was responsible for many innovations in applied traffic engineering, including the Green Wave of coordinated traffic signals..."

(www.revolvy.com)

"During 1965, there was a substantial increase in the application of signalling systems in Croatia, since the company "Nikola Tesla" started to use their own capacities to develop and produce the devices for independent, detecting and co-ordinated control. In 1965, the first "green wave" (phased traffic lights) was installed along the Brace Kavurica Street, controlling traffic by the devices produced in the above mentioned company. The exchange which coordinated the operation of devices was installed in the police building in Dordiceva street. By extending the zone to the two neighbouring directions, two "green waves" (phased traffic lights) were formed in the opposite direction. The main exchange was moved to Marticeva Street. Today, there is a new microprocessing zone exchange which controls all the local signalling devices in the city centre. "

(www.fpz.unizg.hr/traffic)