To monitor traffic. I would think that training their officers to actually and capably direct traffic is more cost effective and productive.
http://www.dominicantoday.com/dr/technology/2016/9/29/60769/Dominican-traffic-cops-unleash-drones-to-curb-chaos#comments
http://www.dominicantoday.com/dr/technology/2016/9/29/60769/Dominican-traffic-cops-unleash-drones-to-curb-chaos#comments