original industrial enameled porcelain steel cautionary sign retired from the chicago transit authority. dates to the late 1940's. original bright red with white lettering. measures 49 x 12 inches. once used one of the chicago "l" rail routes. the chicago transit authority (cta) is an independent governmental agency created by state legislation. the cta began operating on october 1, 1947, after it acquired the properties of the chicago rapid transit company and the chicago surface lines. on october 1, 1952, cta became the sole operator of chicago transit when it purchased the chicago motor coach system. two identical signs available, priced individually.