Radio waves, including those transmitted by Radio 4, travel at the speed of light.

The speed of light is approximately:

* 299,792,458 meters per second (m/s)

* 186,282 miles per second (mi/s)

It's important to note that Radio 4 is a radio station, not a physical object, so it doesn't have its own velocity. The signals it transmits travel at the speed of light.