The agency triumphed in a pitch against Starcom, MediaCom and Arena Media.
Carat, which has worked on the business for ten years, has been appointed with a new, three-year contract. M4C will continue to handle media buying for above-the-line activity.
Mark Hughes, the business director at Carat, said: "We already had a strong relationship with Think! and DfT. That they chose to remain with us for their new strategy is testament to their trust in Carat to unlock the value of media to deliver against their objectives of reducing death and casualties on our roads."
Abbott Mead Vickers BBDO and Leo Burnett have both created recent Think! road-safety campaigns. However, budgets have been hit in line with a reduction in overall government advertising spend.Follow @KatherinePLevy