Automotive Pulse Doppler Maximum unambiguous range?
It depends how the radar is working. If it times the difference between transmission and reception of the pulse, then the correct unambiguous range is given by taking 50mS as the time of flight, and doing the appropriate thing with \$c\$, which gives you 7500km.

However, it's unlikely that is how it's working. It's more likely to be using a higher rate of modulation within the pulse. In that case, you need to take the repetition rate of the actual modulation used to sense the distance.