The objectives of the AI regulatory sandboxes should be to foster AI innovation by establishing a controlled  experimentation and testing environment in the development and pre-marketing phase with a view to ensuring  compliance of the innovative AI systems with this Regulation and other relevant Union and national law. Moreover,  the AI regulatory sandboxes should aim to enhance legal certainty for innovators and the competent authorities’  oversight and understanding of the opportunities, emerging risks and the impacts of AI use, to facilitate regulatory  learning for authorities and undertakings, including with a view to future adaptations of the legal framework, to  support cooperation and the sharing of best practices with the authorities involved in the AI regulatory sandbox,  and to accelerate access to markets, including by removing barriers for SMEs, including start-ups. AI regulatory  sandboxes should be widely available throughout the Union, and particular attention should be given to their  accessibility for SMEs, including start-ups. The participation in the AI regulatory sandbox should focus on issues that  raise legal uncertainty for providers and prospective providers to innovate, experiment with AI in the Union and  contribute to evidence-based regulatory learning. The supervision of the AI systems in the AI regulatory sandbox  should therefore cover their development, training, testing and validation before the systems are placed on the  market or put into service, as well as the notion and occurrence of substantial modification that may require a new  conformity assessment procedure. Any significant risks identified during the development and testing of such AI  systems should result in adequate mitigation and, failing that, in the suspension of the development and testing  process. Where appropriate, national competent authorities establishing AI regulatory sandboxes should cooperate  with other relevant authorities, including those supervising the protection of fundamental rights, and could allow for  the involvement of other actors within the AI ecosystem such as national or European standardisation organisations,  notified bodies, testing and experimentation facilities, research and experimentation labs, European Digital  Innovation Hubs and relevant stakeholders and civil society organisations. To ensure uniform implementation across  the Union and economies of scale, it is appropriate to establish common rules for the AI regulatory sandboxes’  implementation and a framework for cooperation between the relevant authorities involved in the supervision of the  sandboxes. AI regulatory sandboxes established under this Regulation should be without prejudice to other law  allowing for the establishment of other sandboxes aiming to ensure compliance with law other than this Regulation.  Where appropriate, relevant competent authorities in charge of those other regulatory sandboxes should consider  the benefits of using those sandboxes also for the purpose of ensuring compliance of AI systems with this  Regulation. Upon agreement between the national competent authorities and the participants in the AI regulatory  sandbox, testing in real world conditions may also be operated and supervised in the framework of the AI regulatory  sandbox.