traffic police

Mumbai traffic police have a tendency to hide themselves at busy traffic junctions. Now as unsuspecting motorists jump signals, they pounce out of their dens and penalise the offenders.

The simple question here is: What is the purpose of the traffic police? Is it to pemalise offenders and maximise revenue or is it to prevent violation of rules?

In case they wnted to prevent violations, a cop who is very visible would be a great way. If I can see a cop, I would think twice before violating the laws.