Bettors already studying their race cards line up in front of the windows during a busy afternoon at the recently opened off-track betting office in in New York City. So far betting is limited to trotting events. In most of the 29 states which permit horse and dog racing official or unofficial committees are at work studying New York’s experience with its new off-track parlors. Other states, including New York, are contemplating increases in the legal number of racing days allowed each year.