The first aspect he is running away from is the agitation of modern life. The line is quite clear: “And I shall have some peace there, for peace comes dropping slow”. The narrator wants some solitude, some calm and some slowness. The hectic character of modern life, the rat race is not for him.
The second aspect is the disconnection with nature. Indeed, the lines about the beating “heart’s core” “deep” within clearly state that although he is “standing on the roadway or the grey pavement” he yearns for nature, for the “lake, the crickets, the bees, the purple glow of noon”. The binary construction is quite clear, on one end there is the ideal of nature and peace on the other there is the unnatural “grey” and cold disconnection of cities.