Check YOUR Owners Manual
Why? Because it depends on what year build your car is. So for 2014 builds (as the first 4 Series is) different speeds apply as for older models (for the F30 readers).
Therefore check
your online manual to have the correct speed information!
2013 F30 Manual:
"The system issues a two-phase warning of a danger of collision at speeds above approx. 10 mph/15 km/h."
2014 F30 Manual:
"The system issues a two-phase warning of a possible danger of collision with vehicles at speeds above approx. 3 mph/5 km/h."
In the 2014 there is also a "Pedestrian warning with city braking function"
The system issues a warning with brightness staring at approx. 6 mph/10 km/h to approx. 35 mph/60 km/h regarding a possible risk of collision with pedestrians and assists with a brake intervention shortly before a collision.
This makes me wonder if the 2013 builds can be software upgraded to above lower speed detection and to the Pedestrian warning? Does anyone know?