China F1 2015 - Practice 1 and Practice 2 Session Utilisation charts

Here's how the drivers made use of free practice 1:

And free practice 2:

Session utilisation charts are described more fully in a recently released chapter of the Wrangling F1 Data With R Leanpub book. Buying a copy of the book gains you access to future updates of the book. A draft version of the chapter can be found here.