There are many elements that are complementary in the two schemes. They're both on the front of the pack, and I would say that in the U.K. the front of the pack has traditionally been a place for brand values. It has not tended to carry nutritional information for consumers.
So, first of all, I would say having the two schemes on the front of the pack, and using that brand space to communicate simply to consumers about ingredients within the product is a major move forward for manufacturers. They both focus on four core nutrients: fat, salt, sugar, and saturated fat. But the GDA one also has calories, which, as I stated and Professor Sanders also mentioned, is an essential component with regard to the importance of calories in any obesity debate.
They both aim to give consumers a perspective on the food they're eating. The GDA does that by showing consumers how individual nutrients or calories fit into a total diet. The traffic light one does so by showing consumers whether or not the nutrient is high, medium, or low, based on a 100-gram amount. I think the differences are around the fact that GDA is based on portion and traffic lights are based on 100-gram amounts, but there are many similarities between the two.