effort to lure back the passenger car manufacturers, and have the machines more closely resemble cars available to the motoring public. Larger fields were allowed, to as many as 42 cars (up from the traditional 33). The Rickenbacker era coincided with the Great Depression, although the Speedway did not experience significant financial peril, and the engine displacement changes were not in response to the stock market crash. Several Indy traditions were born during this time, including the first bottle of milk in victory lane, the first presentation of the Borg-Warner Trophy, and the tradition of presenting the race winner with the keys to the pace car. Ended with the onset of World War II (Pearl Harbor). The Rickenbacker Era is considered the deadliest period of 500 history, with 24 fatalities amongst competitors and spectators. In response to the numerous fatal accidents, rule changes and track improvements slowly began to be implemented in the interest of safety. The first major national radio coverage of the race occurred in 1928. By 1939, Mutual Broadcasting System was covering the race live to various affiliates across the country. Post World War II era From 1946-early 1950s. Immediately following World War II, the Speedway was sold to Tony Hulman. He swiftly renovated the track which had fallen into a state of disrepair during the war years. It is a brief period, marked by a mix of mostly older cars. Auto racing began to rebuild as a sport after being banned during World War II, primarily due to rationing. By this time, the typical pre-war image of race car drivers as daredevils or reckless stunt drivers had faded. Likewise the mechanics' image as "grease monkeys" or low-level tradesmen faded, as the sophistication of engines and chassis increased. Numerous drivers and mechanics during this time had been involved in the war effort, either stateside or abroad. The legitimacy of the sport recognized on a national level began to grow. National radio coverage of the race began to grow at a fast rate, first by Mutual, and later as a result of the formation of the Indianapolis Motor Speedway Radio Network. Roadster Era From 1952 to the mid-1960s. Considered by many as the "golden era" of the Indy 500, it is highlighted by the participation of the front-engined Roadsters. The first "roadster" is regarded to have been built and entered by Frank Kurtis in 1952. During this time