Traffic signals and signs can increase the flow of traffic and prevent accidents in high-risk intersections. Sometimes, however, an unnecessary signal or sign can actually increase the risk of collisions while slowing traffic.
It's the job of Denver's traffic engineers to study intersections to determine if an intersection needs signals or signs. They compare the conditions at an intersection against national guidelines (often called "Warrants"), and historical data, if available. By looking at the data, they can determine if the intersection is functioning properly, or if changes need to be made to improve the flow of traffic at that point.
As Denver and the surrounding areas grow, traffic patterns shift, meaning that the installation and removal of traffic signals is a constant process.