Costain Group PLC provides smart infrastructure solutions for the transportation, energy, water, and defense markets in the United Kingdom. The company operates through two segments, Transportation and Natural Resources. The Transportation segment operates in the road, rail, and integrated transport markets. The Natural Resources segment operates in the water, energy, defense, and nuclear energy markets. It offers consultancy and advisory, digital technology, climate change, and complex program delivery solutions and services. Costain Group PLC was founded in 1865 and is headquartered in London, the United Kingdom.