The move comes just days after Atkins confirmed it was planning a raft of redundancies at its UK highways and transportation business.

Atkins will fund the American deal from a combination of existing cash reserves and a new £150m credit line from its banks.

PBSJ is employee owned and has around 3,500 staff.

In the year to 30 September 2009 the firm generated profits of US$47 million on gross revenue of US$799 million.

Keith Clarke, chief executive of Atkins, said: “This is an important acquisition for Atkins and forms part of our plan to grow our business through a multi-skill, multi-local strategy.

“PBSJ operates a business model we understand and complements our business superbly, enhancing our skills in environmental, transportation, building design and programme management disciplines.

“PBSJ has an experienced management team and a strong, long-standing reputation for technical excellence and quality, which underpins its deep client relationships.

“These are all important criteria for a successful acquisition which will provide us with a strong platform for growth and enable us to drive significant value for our shareholders.”

Robert Paulsen, chairman, CEO and president of PBSJ, said: “We are excited to be joining Atkins which provides an excellent cultural fit for our business and a great opportunity to further develop our offering.

“We are both focused on engineering excellence and share a clear vision to become one of the world’s best infrastructure consultancies.

“Atkins is a well regarded organisation and we look forward to continuing to drive high standards of work with our clients as part of an enlarged world class engineering consultancy“.