There is way to calculate the speed from the Shadow created my the car
Ull be needing
ARDUINO ( works well for both uno and mega)
And the circuit for it is way too simple
Connect 5V to one leg of resistor.( Connect the other leg (of resistor ) to one leg of LDR . Connect A0 (analog input) to that same leg of LDR. Connect GND to other pin of the LDR.)
The circuit calculates the time of Shadow
And calculate the speed ,app is available for that ,however this idea might have limitation at night
What do think about this ?