Bristol-based SSL provides technology for monitoring and managing traffic, such as identification cameras.
For example, it recently supplied and installed the new system that identifies oversized lorries and hazardous loads approaching the Dartford tunnel in Kent.
SSL was established in 1979 as Simulation Systems Ltd and has 165 employees. Customers include Highways England, Transport for London, the Scottish and Welsh governments and several English local authorities. In the year ended 31st March 2015, SSL generated revenues of £15.1m and EBITDA of £2.0m.
SSL’s senior management team, including managing director Louis Thompson will remain with the business under Costain.
Costain chief executive Andrew Wyllie said: “We are delighted to announce the acquisition of SSL which is in-line with our stated objective of accelerating the growth of business through a combination of organic and acquisitive growth.
“This transaction will further broaden our ability to deliver innovative technology-based solutions to meet the increasingly complex requirements of our major blue chip customers in energy, water and transportation.”