most of the radars (with little exceptions) are set to flash above 80 Km/Hr...so better stay below 80 and that will be more than enough.

Anyway almost "always" there is a sign denoting the speed limit of the road/street and usually it is located a few hundred meters away from the radar.

Also be careful with the so called portable radars, there are a few of them in cars, trucks, and hidden.

In the end stick to the speed limit signs and you'll be safe.

Regards!!