In the scene where Lloyd is driving along Mary while she is in the airport and is singing "Good-bye my Loooovvve" You notice that before he hits the car that he can not finish 'Love' he only says 'Luuu' he cuts off love before he hits the car, so obviously he knows he will be hitting something!
Ian's right. Harry's car hit the other car before the airbag deployed, cutting him off. Then he turns, and the airbag deploys in his face. Hence the comedy. Ha ha.