Automated transportation technology has been rapidly evolving across all modes of transportation, with enormous potential to improve road safety and travel comfort. New challenges arose during the transition to full automation, such as increased instances of disagreements between the driver and the automation system over who should take control. Negotiation plays a crucial role in resolving such conflicts. The Mediator project, a research and innovation programme of the European Union’s Horizon 2020, is developing an intelligent system to meditate between human drivers and highly automated vehicles. This graduation project aims to design a human-machine interaction that can resolve conflicts with appropriate negotiations, thereby creating a pleasant user experience in highly automated vehicles. The challenge lies in striking the right balance between the driver's safety and autonomy in order to ensure that the Mediator system is accepted by a wide range of users. To tackle the challenge, conflicts between human drivers and highly automated vehicles were analyzed to identify the most severe conflict as a main focus. To resolve it, research referred to human-to-human negotiation styles to inspire possible ways of human-to-machine negotiation styles in a context of high automation. To determine the most appropriate negotiation styles, desirable human-to-machine interaction was investigated through interviews.It was found that most participants preferred to have a certain extent of autonomy only when safety is secured. It resulted in an approach of resolving conflicts with negotiation styles based on the reasons for the automation’s takeover requests. More specifically, persuasive negotiation should be employed with a competing style when the reason is about safety. When it comes to comfort, seductive negotiation should be employed with a collaborating style. These insights were translated to interaction qualities for negotiation in the design concept. A design goal was formulated after establishing a future worldview by using the Vision In Product Design (ViP) method. The goal was to create a pleasant experience through negotiation during control conflict. Furthermore, the driver's motivation to follow the automation’s recommendations was investigated through two design interaction cycles. It was found that increasing intrinsic and extrinsic incentives by audio interaction and rewards could effectively motivate drivers to follow recommendations. The final concept is a negotiation ritual consisting of voice messages and rewarding features. When there is a disagreement over who should take over, the negotiation ritual of either persuasive or seductive negotiation will be activated. In the persuasive negotiation ritual, the system will give takeover requests twice, emphasizing the urgency and consequences with a commanding tone and wording. In the seductive negotiation ritual, the system will only ask the driver once, emphasizing the benefit of control transfer with a friendly tone and wording. Furthermore, drivers will get rewards such as parking discounts when following recommendations.