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SECTION 1
Introduction
Drivers generally choose a reasonable travel speed based on their perception of safety and
comfort; a variety of conditions and circumstances, however, can lead a driver to misinterpret
what is safe and comfortable and result in speeds that are undesirably high for the conditions
present at a specific intersection approach. Some of these circumstances are human factors that
may be unique to the individual driver and his or her behavior, and others are physical. Physi-
cal changes to the roadway and surrounding environment may influence driver behavior, which
can indirectly reduce speed and/or enhance environmental quality.
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 effec-
tiveness and implementation considerations. The Guidelines also provide insights into the
relationship between speed and facility operations. There are many popular beliefs about the rela-
tionship 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.
1.1 Intended Users
The Guidelines are designed to be useful to engineers, planners, students, and researchers.
1.2 Purpose of Guidelines
The Guidelines provide information to help users select speed reduction treatments at inter-
section approaches. Although the application of these treatments most often pertains to existing
intersections that experience undesirably high speeds, the information also is relevant to new
intersection designs.
1.3 Scope of Guidelines
The Guidelines apply to intersections with approach speeds of 45 mph or greater. Stop-
controlled, yield-controlled, and uncontrolled approaches to signalized and unsignalized inter-
sections are addressed. Because speeds tend to be lower in urban areas, the Guidelines primarily
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