There are several ways to control vehicular speed on busy roads, perhaps the most being effective being the presence of a traffic control officer where feasible. Another way is installing speed humps and creating roundabouts.  Law enforcement agencies often utilize automated speed enforcement cameras to prevent speeding. Narrowing the roads is another common tactic used towards this end. Radar speed displays that calm traffic and also collect data are yet another tool used to deter speed violators. Installing slow down and speed limit signs is a common solution employed by authorities and communities.  All these speed control measures have their own pros and cons, and their utility and feasibility vary across situations and road/traffic conditions.