COI Communications handled the pitch, details of which were not revealed.
Iris has been briefed to look at ways of extending the campaign message that planning journeys and taking regular breaks can reduce sleepiness.
Iris will sign up partner organisations that can reach a target audience including young men, those driving for business, and leisure drivers at weekends and on holidays. The campaign is also expected to employ direct marketing and below-the-line activity.
The government has an objective to cut road deaths and serious injuries by 40% by 2010. One in 10 car crashes on all of the UK's roads are said to be linked to fatigue.
Steve Bell, director at Iris, said: "By working closely with road safety organisations, we plan to join forces with some of the most powerful and relevant brands for the Think! campaign.
"These brands will not only give us exposure but will ultimately allow us to talk to drivers at those moments when they will be most receptive to a Think!-related message," he said.
The Think! campaign was launched in June 2000 with the aim of getting all road users to recognise that the smallest actions can lead to accidents on the road and that simple steps can be taken to reduce the risk.
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