Description
Purple stop signals was a thing in North America until the 1940's.
These two signals are being used CSX and NORAC (Northeast Operating Rules Advisory Committee)
Approach Normal:
Trains without operative cab signals must proceed on fixed signal indications not exceeding 79 MPH.
Clear to Next Interlocking: CSX version
Trains without operative cab signals must proceed on fixed signal indications not exceeding 79 MPH, approaching next home signal prepared to stop.
Clear to Next Interlocking: NORAC version
Trains with inoperative cab signals, automatic train stop or speed control must proceed on fixed signal indication, (and cab signal indication, if operable) not exceeding 79 MPH. Trains with inoperative cab signals must approach the next home signal prepared to stop, unless Approach Normal(Rule 280-B) is displayed on a distant signal prior to the home signal.