The bill introduces comprehensive regulations for harness horse racing in Massachusetts, overseen by the Massachusetts Gaming Commission. Key provisions include the implementation of a three-light warning system for accidents, the establishment of a "Horsemen's Account" for financial transactions related to purses and stakes, and the requirement for licensed associations to submit a complete list of employees to the Commission. It also details the responsibilities of racing officials, emphasizes horse health and safety through the creation of a Veterinarian's List, and sets forth licensing requirements for drivers, trainers, and owners. Additionally, the bill mandates testing for prohibited substances, outlining procedures for sample collection and handling.

Further amendments focus on claiming procedures for horses, allowing claims to be voided under specific circumstances, and establishing new eligibility requirements for veterinarians, including restrictions on wagering. The bill mandates postmortem examinations for horses that die or are euthanized on association grounds and requires a mortality review process to gather information surrounding each racehorse's death. It also addresses environmental contaminants affecting horses and adopts the United States Trotting Association Rules, ensuring Massachusetts regulations take precedence in case of conflict. Overall, these measures aim to enhance the integrity and safety of harness horse racing in the state.