查查wiki的说法。

Average speedsEdit
Speeds achieved on indoor tracks are usually greater than those on roads. Other factors affecting speed are the route profile (flats and hills), wind conditions, temperatures and elevation. At a 2013 event in Mexico, Fran?ois Pervis achieved an average of 21.40 metres per second (77.0 km/h; 47.9 mph) with a flying start over 200 meters. The top average speed over the men's 1 km time trial at the 2004 Summer Olympics was 16.4 metres per second (59 km/h; 37 mph) recorded by Chris Hoy. Average speeds clearly drop with increasing distance, so that over the 120 km Cootamundra Annual Classic it is 11.8 metres per second (42 km/h; 26 mph). In the 259 km 2010 Paris-Roubaix, Fabian Cancellara set a speed of 10.9 metres per second (39 km/h; 24 mph), while over the 818 km Furnace Creek 508, the speed drops dramatically to 8.3 metres per second (30 km/h; 19 mph). For an extreme road distance such as the 4800 km Race Across America, the average speed of the record holder is 5.7 metres per second (21 km/h; 13 mph), while the 2350 km Freedom Trail over mountainous terrain in South Africa is at a record speed of 1.9 metres per second (6.8 km/h; 4.3 mph).


一天40miles, 分两次骑，平均每次20 miles，也就是32公里左右。根据上面所述男子自行车赛车世界纪录，在不同的距离段，有不同的速度纪录。一公里赛程，最快均速是37 mph. 120公里赛程，最快是26 mph. 这只是一个reference，是人类至今所能达到的最快速度的衡量。注，取得这些纪录的是（1）男人 （2）专业运动员 （3）有不经查实的故事说，很多竞赛车手服用药物。那一个业余女生骑车，三十二公里的车程，时速是否能达到20mph? 我看悬。