Leiden University invites applications for a fully-funded PhD position focused on the intersection of artificial intelligence, traffic management, and decision support systems. This research opportunity is part of a collaborative project between Leiden University and Technolution, embedded within a larger consortium involving both academic and industry partners. The successful candidate will join the Leiden Institute of Advanced Computer Science (LIACS), a leading computer science department in the Netherlands, and work closely with Prof. Rob V. van Nieuwpoort (Leiden University) and Tijs van Bakel (Technolution). The project aims to advance the application of foundation models, including large language models (LLMs), to support and enhance real-time decision-making in road traffic management. Research activities will include adapting and fine-tuning LLMs for spatial-temporal data and traffic control domains, developing hybrid AI architectures that integrate symbolic reasoning, real-time data streams, and probabilistic inference, and designing decision support tools capable of natural language interaction, scenario simulation, and action explanation. The study will also address efficiency, robustness, generalization, and ethical implications of deploying foundation models in safety-critical infrastructure. As a PhD candidate, you will conduct original research, publish in peer-reviewed journals, present at international conferences, and complete a PhD thesis within four years. You will collaborate with researchers and developers at LIACS, Technolution, and the broader project consortium, and may assist in relevant teaching activities. The position offers a stimulating and international environment, with access to the Bio Science Park, one of Europe’s largest science parks, and a vibrant academic community. Applicants should hold (or be close to completing) an MSc in computer science, AI, or a related field, possess strong programming skills (Python, PyTorch), and have experience with modern machine learning frameworks and large-scale models. An interest in interdisciplinary research, excellent analytical and communication skills, and fluency in English are essential. The university values diversity and inclusivity, and encourages candidates from all backgrounds to apply. The position is fully funded, offering a competitive salary (€3,059–€3,881 gross per month), holiday and end-of-year bonuses, pension scheme, full reimbursement of public transport commuting costs, flexible working hours, options for sabbatical or paid parental leave, hybrid working arrangements, home-working allowance, and a university-provided laptop. The initial contract is for one year, with extension to four years upon positive evaluation. To apply, submit your application via the official university careers portal before December 18, 2025. For academic inquiries, contact Prof. Rob van Nieuwpoort at [email protected]. For procedural questions, email [email protected]. More information about the application process and employment conditions is available on the university website. This is an excellent opportunity for motivated researchers interested in cutting-edge AI applications for traffic management and decision support, within a supportive and innovative academic environment.