Do traffic lights help in preventing accidents?

... apparently not always.

Here we will not talk about traffic jam in our busy cities, but rather... sandwiches.

In the debate between mandatory regulation and "soft" approaches, one interesting case is that of "traffic light labelling", one of the available models to provide consumers information about the food they are considering to by straight from the packaging. At the moment, several of these models are used in practice, the most spread being the classic GDA label- which specifies the contribution of a certain amount of the product to the average (advised) daily intake of nutrients, salt and so forth.

According to a study by the British association which?, this cohabitation of styles makes it difficult for consumers to compare similar sandwiches from different store chains, which might opt for the one or the other label.

Traffic light labels are supposed to draw the consumer's attention to specific features, such as an high salt of saturated fat content,  by showing them in red area to make clear that, e.g., pizza is a "treat" rather then standard, every day food.  The usage of similar labels, according to the UK government, should be reviewed to achieve more transparency through consistent information provision.

Is more uniformity needed outside the UK as well?