OK, I just looked through 4 books on B&O passenger trains in the 1940s, 50s, and 60s. Nearly all of the pictures that clearly showed station platforms showed no safety lines. Exceptions were at the Elizabeth, NJ wooden platform in 1958 (white), Fort Street Union Depot in Detroit in 1964 (yellow), Chicago and Northwestrn Station in Chicago in 1969 (color?), and Chillicothe in 1965 (looks yellow?). Many stations clearly did not have lines in the early 60s, including Union Station in DC in 1960, Silver Spring station in suburban Maryland as late as 1967, Parkersburg in 1970, and Camden Station (Baltimore) in 1967, Keyser in 1968 and Grafton in 1969. In contrast to the CNW Chicago Station, the Chicago Grand Central Station did not have safety lines as late as 1969. The brick platform at Point of Rocks does not appear to have any lines in 1990, but the macadam platform across from it has a broad yellow area along the track edge in 2006.
At least these photos are consistent with my memory. So, did I pass the Alzheimer's test? Wait, what were we talking about?