you dont understand.. in the US, this is how most of the smaller towns get their money. they pay a single patrol car to sit on their section of highway all day and pull people over for speeding. a speeding ticket in the us is up to 300$ in some places. noone ever gets pulled over for speeding in large cities because it is a waste of time. the whole speeding ticket system is a scam that has absolutely nothing to do with safety.(at least on highways).
Not sure (or care) what "large city" you live in where no one gets a ticket. I live in the largest city in my state which is in the top 30 populous cities in the nation. Our police force has several officers in modified sports cars whose only job is to write tickets, almost exclusively on the interstate system. These guys are so infamous that the local paper did a Sunday feature on the top ticket writer, after he pulled over a local DJ for speeding and the DJ told everyone the officer acted like an arrogant jerk while writing the ticket. The police officer filed suit against the DJ and it was never heard in court. The officer bragged about the number of tickets he wrote in a year which was well above 1000. He also admitted he let his "brothers in blue" get a pass as they were driving 20+ MPH over the limit on the same interstates, according to the speed gun the reporter rented for the story. The fines start at $50 plus court costs so do the math. So that tinted out Dodge Charger or IROC Camaro might be one of our officers about to turn on all the hidden lights.