These Guidelines provide relevant information about the effects of speed, the conditions that
may contribute to undesirably high speeds at intersection approaches, and the state of the practice
related to speed reduction treatments used in the United States and abroad—including their effectiveness and implementation considerations. The Guidelines also provide insights into the relationship between speed and facility operations. There are many popular beliefs about the relationship between speed and safety, and it is common for people to assume a direct relationship between the two. In fact, there is little published data to actually link speed with safety performance.
This report does not discuss whether speed reduction is appropriate for a condition or what amount of reduction is necessary. This document assumes that the user already desires reduced speeds. The Guidelines provide users with information about speed, speed considerations at intersections, and the potential application of treatments to affect speed. Additional research is needed to fully understand the effects that speed reduction treatments and reduced speed may have on safety.