In Ohio at least, part of this is related to the demise of Mayor's Courts. Back in the day, when a ticket was issued, the case went before the city mayor, who decided guilt/innocence and also the fines and punishment. This is why so many departments got the reputation for being speed traps and ticket happy. And, this was in large part true. You had the man in charge of the budget making decisions that directly impacted the income to the city. Higher income to the city meant higher police budget. Higher police budget meant better toys. A few years back, it was ordered that magistrates be appointed by the city to run mayor's courts, taking the mayor out of the picture. Income still goes to the city, but you have an independent magistrate making the decisions. This improved things to a degree, but also started the trend to eliminating mayor's courts, as many cities didn't want to pay a magsitrate (around $1,000 a month minimum) when they could just send all of the tickets to Municipal Courts with real judges at no expense. Pro is no cost. Con is no income. So, there's no motive for an officer to go write a ton of tickets any longer.
I run traffic court once a week, and I see the trend coming through here. We're down from averaging 20 tickets a wek to 10-15 a week. In talking with the officers, they say that people truly aren' t driving as fast. Maybe the cost of gas is having an impact...