Smart transportation systems are revolutionizing urban mobility by leveraging technology to optimize traffic flow, enhance safety, and improve user experience. Central to the success of these systems is Human-Centered Design, which focuses on the needs, behaviors, and experiences of users. This paper explores the role of Human-Centered Design in smart transportation systems, examining its principles, benefits, and challenges. Additionally, we propose a comprehensive model that integrates Human-Centered Design into the development and implementation of smart transportation solutions, using Helsinki’s Mobility as a Service (MaaS) initiative as a case study.