I've never understood that one. Perp is in a vehicle gets pulled over, cop gets out and perp jumps back in vehicle and takes off, cop hauls ass trying to catch him which causes perp to drive like a madman just like the cop putting everyone's life in the vicinity in danger. Is it really that worth it? Get as much info as possible, let him go, investigate and find the asshole then put him in jail for a longer time.