You would basically have to ask each railroad when they stopped using fuel rear markers. Electric markers started in the mid 1950's but some going to reflectors as rear markers. Some rear end accidents occurred when reflectors were used because unless a head light had a straight shot it it would not reflect the light. Many railroads were slow to equipment cabooses with electric power to light the markers staying with reflectors or during the day red flags. Even when electricity was installed for use of radios, markers lagged behind..