蜗牛骑驴上高速
[wō niú qí lǘ shàng gāo sù]
It is a whimsical combination translating literally to 'Snail Riding Donkey On Expressway', which humorously juxtaposes something very slow (snail, donkey) against something modern and fast (expressway), likely implying someone out of place but moving along nonetheless.