This needs a statistician...
If you look you can see the 100m posts on the right-hand side. I counted 30 (3km) between 19s and 1m13s, which works out at an average of 208 kph.
I then shuttled back through noting the speedo readings every second over the same segment. Apart from half a dozen obscured ones, the average was 229 kph, which is +10%. Typically, speedos read about 8% fast and the residual error is negligible, or due to an extra tooth on the rear sprocket.
1-4 The Road