Let the speed be x m/s. According to the meaning of the question,

△ABC is a right triangle with ∠C as the right vertex,

And BC=2x km, AC = 30m, AB = 50m.

Then (2x)? +30? =50?

The solution is x=20.

∴ The vehicle speed is 20m/s, that is, 72km/h > 70km/h.

The car was speeding.