"Caltrans" traffic signal arms

[capt.ron]

Apologies in advance if I put this in the wrong topic section.
Anybody know when Caltrans (or whoever) began to use its modern traffic signal arm? Modern as in from the late 1970's onward (or whenever they began to be commissioned). Example in the link below:
https://www.google.com/maps/@33.8471552,-117.9240882,3a,75y,52.92h,90.72t/data=!3m6!1e1!3m4!1sczlPpQ4HR_7yjddUbgDXRQ!2e0!7i13312!8i6656

Also I see this same traffic signal arm in use in other southwestern states as well (AZ,UT)
Kingman, AZ
https://www.google.com/maps/@35.2242688,-114.0036455,3a,75y,35.74h,82.28t/data=!3m7!1e1!3m5!1smr9sSOrxNk3AiR2PrCEgOA!2e0!6s%2F%2Fgeo1.ggpht.com%2Fcbk%3Fpanoid%3Dmr9sSOrxNk3AiR2PrCEgOA%26output%3Dthumbnail%26cb_client%3Dsearch.TACTILE.gps%26thumb%3D2%26w%3D392%26h%3D106%26yaw%3D225.5732%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656

I also see this traffic signal arm used frequently as one approaches a truck weigh station. Marion / West Memphis, AR I-55 southbound:
https://www.google.com/maps/@35.2049892,-90.2043655,3a,75y,180.34h,91.08t/data=!3m6!1e1!3m4!1s0VYhf1P_JPF6mv_lmJculw!2e0!7i13312!8i6656
I find it rather odd to find this traffic arm in Arkansas, since they normally use the straight arm in Arkansas, which is found in lots of locales.
https://www.google.com/maps/@35.2125773,-90.2065783,3a,75y,152.51h,93.3t/data=!3m6!1e1!3m4!1stL0K2INgtd4ruZ1fx7wI_A!2e0!7i13312!8i6656

[Otto Yamamoto]

1968

XT1585