It is perfect for Physical Journey. In the text, 3 characters represent 3 different aspect towards journey. Toad is a character who loves to travel,who is enthusiamsm and optimism. In the other hand, Rat is a character who has a negative attitude to journey. And in the middle, we have Mole, who is undecisive and hesitating about going on a journey.
The author has used various techniques to convey the idea of journey throughout the text such as : powerful imagery, emotive words,etc. He has represented a active, physical journey by using a lot of colourful images sucs as :"yellow, green and red wheels". Also, images like "open road, dusty highway, gipsy caravan" symbolises the journey with many possibilities. The list of places like :"Camps, villages,...cities" shows the variety of physical journey. With 7 exclamation marks, the author has emphasize the anticipation and enthusiasm of Toad towards journey. Unlike Toad, Rat "only snorted and..... remanining where he was" display such a negative mind about taking on a journey. Rat symbolises for those who don't want to move away from everyday routine :"I'm not going and that's flat". Anthropomorphism (or personification ) is used successfully to conveys the idea about journey more general.
Hope that helps