As cities continue to expand, railways are expected to become an important component of urban mobility systems. Compared to automobiles and air transport, railways are highly energy efficient and produce relatively low environmental impacts and therefore form an important component of sustainable transportation systems. Thus, researchers have been exploring advanced train control technologies for further improvement of operational efficiency, passenger comfort, and punctuality while reducing energy consumption.

In this context, Professor Masafumi Miyatake from the Department of Engineering and Applied Sciences in collaboration with doctoral student Mingyu Lyu from Graduate School of Science and Technology, Sophia University, investigated a new AI-based framework for urban railway speed control. The findings were published in Volume 14 of IEEE Access on March 25, 2026.

Reinforcement learning is a branch of artificial intelligence (AI) which has attracted attention as a promising approach for automatic train operations as it enables an AI agent to learn optimal control strategies by interacting repeatedly with an environment and improving its behavior through trial and error. However, implementing this in railway operation presents several practical challenges including incomplete information about operating conditions, train inertia, braking delays, and strict safety requirements.

To overcome this, researchers developed a recurrent reinforcement learning framework based on Recurrent Soft Actor–Critic (RSAC) algorithm. RSAC is an AI method that enables train control systems to learn from past driving patterns and adapt to changing railway conditions over time.

“Our reinforcement learning-based algorithm was capable of adapting train driving control to a wide range of track and rolling stock conditions,” explains Prof. Miyatake.

Unlike conventional reinforcement learning methods, the proposed approach used a recurrent neural network that can retain information from previous train states. This allowed the system to capture time-based relationships associated with train operation, such as traction response delays, braking history, and inertial effects, thereby improving decision-making under partially observable conditions. The team also used a training approach that allowed the AI system to first learn from examples of expert driving behavior before learning on its own. By studying these optimized driving patterns early in training, the AI was able to learn faster, make better decisions, and develop more stable and efficient train control behavior.

Apart from this, the team also integrated a safety filter into the framework. The safety filter would override potentially unsafe control commands generated by the AI policy and ensure compliance with the operational constraints such as speed limits and braking feasibility. This mechanism also helped ensure safe operation when the learned policy encountered unfamiliar situations.

The proposed framework was evaluated through various simulations of urban railway operations over approximately two-kilometer sections between stations. The simulation environment was designed to closely resemble real-world railway conditions, including uphill and downhill tracks, changing speed limits, and required train arrival times.

Additionally, the proposed AI framework was also compared with several other widely used reinforcement learning algorithms. These included Deep Deterministic Policy Gradient (DDPG), Proximal Policy Optimization (PPO), Twin Delayed Deep Deterministic Policy Gradient (TD3), and Soft Actor–Critic (SAC), which are commonly used to train autonomous decision-making systems.

“Among all the methods tested, our developed framework learned faster and performed better than all tested methods,” explains Prof. Miyatake.

The research also demonstrated strong energy efficiency. While dynamic programming achieved the theoretical minimum energy consumption under ideal conditions, the developed system attained comparable performance while remaining suitable for real-time operation. Meanwhile, conventional reinforcement learning approaches exhibited less stable behavior and higher energy consumption.

The findings suggest that this framework could help introduce a cleaner and more convenient public transportation by facilitating accurate and energy-efficient train operation at relatively low cost. The study refines the advantages of railways as an energy-efficient and environmentally friendly transportation system contributing towards a sustainable future. Looking ahead, the study may contribute to enhancing the role of railways as a sustainable transportation system—supporting climate change mitigation and sustainable urban development.

The findings also highlight the potential of AI-driven railway systems to support safer, greener, and more reliable urban transportation in future smart cities.

Dr. Masafumi Miyatake is a Professor and Chair of the Department of Engineering and Applied Sciences at Sophia University. He earned his Bachelors, Masters, and Doctorate in electrical engineering from The University of Tokyo. His research focuses on energy management, renewable energy, power conversion, and transportation electrification, particularly for railways and electric vehicles. Till date, he has published more than 300 research articles and is also known for his work on smart and energy-efficient transportation systems. He is a Member of IEEE and a Senior Member of IEEJ.

Funding Information

This work was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI under Grant 23K03822.

Media Contact

Office of Public Relations, Sophia University (sophiapr-co@sophia.ac.jp)

Pursuing early graduation on the path to becoming a researcher

――Why did you choose the Faculty of Science and Technology at Sophia University?

When I was five, my mother was diagnosed with a rare disease for which there was no effective treatment. That experience led me to decide to pursue a career in pharmaceutical science. I came to believe that addressing diseases modern medicine cannot yet cure requires new scientific approaches. In my first year of high school, I became interested in two advanced fields, biophysics and nucleic acid therapeutics. When I learned that Sophia University was the only institution in Japan conducting research that integrates these two areas, I decided to apply. I was also drawn to Sophia’s curriculum, which allows students to continue studying across a broad range of disciplines rather than narrowing their focus too early.

――What mindset have you had as you worked toward becoming a researcher?

I work toward big goals by breaking them into smaller steps and focusing on what I can do next. I read many specialized books, and since my first year of high school, I have looked for information on my own and joined university seminars and study groups to deepen my learning. From a young age, I tended to ask “why,” and when I did, my mother would ask me in return, “Why do you think so?” I believe those conversations helped me develop the habit of questioning and exploring ideas.

――What class made a lasting impression on you during your undergraduate years?

It was a class called History of Japanese Dictionaries, one of the University-wide General Education Courses. The class explored history through dictionary definitions, which clearly reflected the social context of each period. We examined the same words in dictionaries from different eras, from the past to the present, and connected changes in meaning with their historical backgrounds. By linking individual ideas and seeing how they expanded into broader perspectives, the class helped me broaden my view. I feel that this process of questioning and clarifying the logic behind things is one of the defining features of university learning.

――Now that you are a graduate student, how did you learn about the early graduation program, and what was your student life like at that time?

I stayed focused on my goals while making a conscious effort to keep an open mind. I spoke with professors from a range of laboratories, including those in chemistry and biology, to explore different research areas. Through these conversations, I learned about the early graduation option for students planning to pursue a doctoral degree. I first became aware of it in the summer of my first year, and from then on, it became a clear goal. Having this goal kept me motivated and deeply engaged in my studies. My third year was demanding, however, as I balanced coursework, experiments, and research while preparing to graduate early.

Innovating Treatments for Intractable Diseases Through Biophysics and Oligonucleotide Therapeutics

――Could you tell us about your research?

My research focuses on nucleic acid therapeutics from a biophysical perspective. Nucleic acids refer to DNA and DNA‑like molecules, and nucleic acid therapeutics are drugs developed using these molecules. Biophysics applies physical principles to biological systems, and my work centers on analyzing the three-dimensional structures of these molecules.  Designing drugs based on molecular shape allows researchers to rationally create new types of treatments that may be effective even for intractable diseases. For this reason, I work on both fundamental research to understand the structures of nucleic acids and applied research that uses these insights to design new nucleic acid therapeutics.

――What is your life like as a graduate student?

Graduate school feels completely different from my time as an undergraduate, as research now takes center stage. In my case, the work is highly independent, so I develop my own plans and move my research forward with considerable flexibility. Early graduation has also given me the chance to connect not only with peers in my cohort but with students a year ahead of me, which has been a meaningful part of my experience. At this point, I hope to pursue a career as a researcher in academia. What I find especially rewarding about this environment is not just the academic freedom it offers, but the opportunity to work closely with professors who have truly mastered their fields. Being surrounded by people with such deep knowledge and experience continually pushes me to improve, and I feel this has played a significant role in my personal growth.  

――What message would you like to share with current students?

Graduate school is a place where you can fully immerse yourself in research. There is real excitement in building on what you have learned, exploring new ideas, and charting your own path. I hope you stay curious, keep an open mind, and continue to challenge yourself.

My first academic conference presentation

In 2024, I attended academic conferences for the first time, including an international conference on nucleic acid chemistry. Presenting my research gave me the opportunity to exchange ideas with researchers from around the world, including leading figures in the field. These experiences were not only valuable in helping me think about future research directions, but also truly exciting! The photos here were taken at a meeting of the Crystallographic Society of Japan, where I presented both orally and through a poster session, and was honored to receive an award.

※Please note that the content of this article is correct as of October 2024

Sophia University has a longstanding relationship with the Ashinaga Foundation. In 2011 and 2014, the University entered into memoranda of agreement with the Foundation to accept students it supports from abroad as scholarship recipients and has since welcomed a number of such students. Building on these past initiatives, the newly concluded partnership agreement reaffirms and further strengthens the framework for cooperation between the two organizations through this renewed agreement.

Under this partnership, Sophia University will continue to accept orphaned students supported by the Ashinaga Foundation as scholarship recipients and will provide comprehensive support for their academic pursuits and broader student life. This initiative reflects Sophia University’s strong alignment with the Ashinaga Foundation’s mission: to offer both material and emotional support to all orphaned children and, through education, to cultivate individuals with a strong volunteer spirit who can contribute to global society. Grounded in its tradition of Christian humanism, Sophia University will work in close collaboration with the Foundation to advance these shared goals.

Commenting on the agreement, President Miki Sugimura stated:

“I am truly delighted and honored that Sophia University has been able to conclude this partnership agreement with the Ashinaga Foundation. When I visited the Foundation’s headquarters for the signing ceremony, I had the opportunity to learn about its history since its establishment and was deeply impressed by the dedication of all those who have supported its activities. Their commitment to standing alongside others and providing mutual support through compassionate care resonates strongly with us. I also feel that this philosophy has a natural affinity with Sophia University’s educational ethos, ‘For Others, With Others,’ which lies at the heart of our Jesuit Catholic foundation. Through this agreement and beyond, I hope that, while cherishing our respective missions, we can continue to walk together in nurturing the next generation. I sincerely wish the Ashinaga Foundation continued growth and success.”

Looking ahead, Sophia University will further enhance its scholarship and educational support initiatives in cooperation with the Ashinaga Foundation under this agreement. Through these efforts, the University remains committed to fostering individuals who can work collaboratively with empathy for others and who embody the spirit of “For Others, With Others.”

As someone majoring in Latin American politics, I felt it was only natural to step outside my original “Japanese” perspective and experience life in the Hispanic world firsthand. Since entering Sophia University, studying abroad had always been something I considered essential.

Although Chile transitioned from military dictatorship to democracy more than 30 years ago, the country is still often described as socially divided. I chose Chile because I believed interacting with people living within such a context would offer new perspectives for my research in Latin American politics.

I had heard that Chilean Spanish is so unique that even native speakers from other Spanish-speaking countries sometimes struggle to understand it. Because of that, language was my biggest concern.

Also, Chile is still a relatively uncommon destination for international students, so there was limited information available. Both my parents and I felt anxious at times because of the uncertainty.

I came to realize that conversational language skills and the language skills required in academic settings are completely different. Grammar, for example, is often underestimated, but it cannot simply be picked up naturally after arriving abroad. With that in mind, I studied systematically beforehand, and as a result, I had very few academic regrets once I arrived in Chile.

The university’s main campus was enormous—locals even described it as “like a small city.” Because of Chile’s complex social and political situation, I found local students to be highly politically aware and socially engaged.

People often imagine overseas universities as places full of active discussions among students, but in reality, many classes were lecture-based. There were also fewer reaction papers and group discussions than I had expected.

Without question, Chile’s extraordinary natural diversity impressed me the most. From the Atacama Desert in the north—the driest desert in the world—to central beach resorts, the freezing landscapes of Patagonia in the south, and even Easter Island with its tropical climate, traveling across Chile almost feels like traveling across the entire world.

While traveling in Buenos Aires, Argentina, I witnessed events related to the political situation in Venezuela. The city’s iconic Obelisk was illuminated in the colors of the Venezuelan flag, while many Venezuelan refugees gathered to celebrate. It became a profound moment for me to reflect on the meaning of democracy.

I became involved in a serious housing contract dispute. Fortunately, it was an extremely rare case, so future students should not worry too much.

At first, I tried to resolve the issue on my own, but eventually I felt unsafe and contacted the Japanese embassy. They supported me wholeheartedly until the day I returned home.

Many of my friends and I shared strong interests in politics and history, so we often discussed sensitive topics. Sometimes our opinions clashed. What I realized through those experiences was that no matter how uncomfortable or disagreeable someone’s opinion may seem, it is impossible to truly understand an issue without first understanding the background that led them to those beliefs.

This realization fundamentally changed the way I think, and I believe it will continue to influence both my future research and personal relationships. In fact, for my graduation thesis, I plan to write about a Chilean political group that I once felt a strong resistance toward.

There are many reasons people hesitate to study abroad, such as job hunting or financial concerns. However, because this stage of life is such a formative and emotionally sensitive period, studying abroad can undoubtedly provide entirely new perspectives and possibilities for the future. I truly encourage fellow students to consider it positively.