LED Matrix Sign displaying speeds from a RADAR module

Description

We are looking at options for controlling the speed of Junior Kart racers entering the pits at our local race track.
The scope is to identify a suitable coast effective radar module and identify a suitable readily available LED matrix display controlled by an Arduino type microcontroller, describe the wiring and provide the code to allow us to detect kart speeds at a distance of around 10m to 30 m and display it on an LED matrix to inform the drivers and marshals of their speed.
We only need three hardware to specified and the software written with general wiring descriptions. We will then build and enclose the electronics as we see fit.
happy to discuss options with anyone interested in helping.Manu thanks.