Belgian braces!

I was happily (sic) driving along a major road the other day and saw the above message on the back of a bus the other day: "Le chien s'échappa, Lucas voulut le rattra...". The word "chien" caught my eye so I tried to get closer to the bus to see what it was all about. This was during rush hour so some risk-taking was involved. Straining my eyes to focus on the text, wondering what was being advertised or what the message meant, if anything. I should have been focusing on the road and the other road users which is advisable in Belgium more so than anywhere else. I never caught up with the bus and had to wait for another occasion. I saw the same text for a second time a couple of days later in equally difficult driving conditions. I still could not make out what it meant and asked myself a series of questions. What has the dog got to do with it? Who is Lucas? Why is the word "rattraper" shortened to "rattra...". I decided to check it out on the internet. Well, it seems the message is supposed to encourage drivers not to exceed the speedlimit of 50km/h. Is this new? Any Belgians out there who know more about this? Your comments are most welcome.
The IBSR, the Belgian Road Safety Institute, is behind the advertising campaign. Their aim is to improve road safety and this is how they want to get their message across: I quote: "through a clear message which should be specific and one-dimensional, short, convincing, credible, clear, catchy, concrete, realistic". Talk of missing the point! And yet, the IBSR is quite capable of getting the message across. See picture of motorway billboard on the right. The caption says: " What about your belt?". How dangerous is that?