Costain Group PLC is a United Kingdom-based sustainable infrastructure solution company. The Company is focused on four key markets of the United Kingdom with long-term investment in infrastructure: transport, water, energy, and defense. The Company operates through two segments: Natural Resources and Transportation. Its sectors include road, rail, integrated transport, energy, water, and defense and nuclear energy. Its road sector provides a full range of services to support investment across the road network, increasing capacity, cutting emissions and supporting the United Kingdom economic stability. Its energy sector creates and delivers energy security for the United Kingdom with focus on energy transition, energy resilience, and energy connectivity. The Company is involved in research and development in its highways, integrated transport, aviation, energy, defense, water, and rail sectors.