I’m not so concerned about foods that emit foul smell before eating, but the ones that do afterwards. Considering that it’ll take some time after digesting for the gas pressure to build up, it is preferable that the passengers digest food just before entering a bus/tram/train, generate gas while traveling and let it out only after their ride. Logically, the signs should oblige the passengers to eat at platform, not home.
On the other hand, passing gas (preferably with a fanfaire) gives you a good laugh, especially in confined and poorly ventilated places, with lots of people around you. Perhaps the ones who hung the signs were after that, who knows.
(Could I have my coat, please, and I’ll see me out. Yes, the one with a sandwitch in each pocket,)