The main purpose of the Improving Accessibility Through Microtransit Act is to enhance transportation options for individuals with disabilities or mobility impairments. It aims to establish a pilot program that provides competitive grants to various entities to improve accessible microtransit services, which are small-scale, flexible transportation options that can be tailored to the needs of users. Key provisions of the Act include the establishment of a pilot program by the Secretary of Transportation, which must be set up within 180 days of the law being enacted.