Actually, they ran a story on this in local news a year or so ago. The police chief was questioned about quotas. He said that they do not have quotas. However, they do offer bonuses for officers that have a certain number of successful traffic citations per month. (to clean up the streets and line the city's pockets...)
So the answer to your question, yes....quotas exist. The powers that be may not ackowledge it, but it is an active motivation for many officers since most don't like to write tickets.