Dangerous Ages by Rose Macaulay

On the road it was the same. Nan, with only the faintest, if any application of brakes, would commit herself to lanes which leaped precipitously downwards like mountain streams, zigzagging like a dog's-tooth pattern, shingled with loose stones, whose unseen end might be a village round some sharp turn, or a cove by the sea, or a field path running to a farm, or merely the foot of one hill and the beginning of the steep pull up the next. Coast roads in Cornwall are like that -- often uncertain in their ultimate goal (for map-makers, like bicyclists, are apt to get tired of them, and, tiring, break them off, so to speak, in midair, leaving them suspended, like snapped ends of string). But however uncertain their goal may be, their form is not uncertain at all; it can be relied on to be that of a snake in agony leaping down a hill or up; or, if one prefers it, that of a corkscrew plunging downwards into a cork.

Nan leaped and plunged with them. She was at the bottom while the others were still jolting, painfully brake-held, albeit rapidly, halfway down. And sometimes, when the slope was more than usually like the steep roof of a house, the zigzags more than usually acute, the end even less than usually known, the whole situation, in short, more dreadful and perilous, if possible, than usual, the others surrendered, got off and walked. They couldn't really rely on their brakes to hold them, supposing something should swing round on them from behind one of the corners; they couldn't be sure of turning with the road when it turned at its acutest, and such failure of harmony with one's road is apt to meet with a dreadful retribution. Barry was adventurous, and Kay and Gerda were calm, but to all of them life was sweet and limbs and bicycles precious; none of them desired an untimely end.