There is a clear analysis in the latest Road Traffic Estimates:Great Britain 2017. Have extracted page 1 and the cycling bits and attach them below. A valuable professional view that contrasts with the very optimistic statements of British Cycling, Cycling UK and others.
Total mileage is going up linearly, but at just 30% in 20 years, so about 1.5% each year. But numbers of cyclists are not going up. It is just the same number cycling a bit more each year.
We need to face up to the failure of the many initiatives to promote cycling and maybe think a bit outside the box. Bit more information and a chance to comment in the linked blog.
Looking more closely at the data shows that the increase in mileage is largely in Inner London. Away from Inner London the trend is very weak or zero. More on this in a later blog. Population surveys agree with the traffic data. Numbers of cyclists actually fell significantly over the first 2 years of Sport England's Active Lives Survey.
Seems to me important to face up to the failure of the many initiatives to promote cycling over recent years. Time to start thinking "outside the box".