A homogeneous segment includes consistent design characteristics (i.e., cross section) and uniform traffic volumes. Segments are generally considered to be the roadway between intersections and are homogeneous throughout the segment otherwise, the distance would be subdivided. Traffic volumes and physical characteristics generally remain the same over the length of a segment, although small variations may occur (e.g., changes in traffic volumes on a segment resulting from a low-volume driveway). SegmentsĪ segment is the length of roadway between two points with similar geometric, operational, and vehicular characteristics. ![]() Points (more commonly called intersections) can be subdivided as the following:ĭepending on the variables included in an agency’s database, a crash may be coded as being “intersection related” or “not intersection related.” Such a variable could help determine if the crash should be associated with the characteristics of an intersection or of a segment. Points are places along a facility where (1) conflicting traffic streams cross, merge, or diverge (2) a single traffic stream is regulated by a traffic control device or (3) there is a significant change in the segment capacity (e.g., lane drop, lane addition). The following sections provide additional descriptions. In general, a network element is typically one of the following:įigure 4 shows examples of the network elements. The network element scale may start with the smallest increment, typically an intersection or a marked crosswalk (point), and then be grouped into larger scales to form a facility or an area. For example, an advertising campaign regarding driving under the influence may want to target the entire community if the message is being distributed by radio or target select intersections if the message is being distributed using a print medium. The scale and type may be related to the anticipated treatment. ![]() The scale of the network being studied along with the type of site(s) for a safety assessment can vary. After the performance measure is selected, the type of screening method needs to be identified.įigure 3. The preference is to select a performance measure that does not have a known bias or that can minimize known biases. This decision could affect how the crash and roadway data are gathered and processed along with the type of performance measure(s) used to identify sites. The planning of the assessment includes the following three substeps as shown in figure 3:Īn initial step is to determine the type of the network elements being studied or the scale of the network. For communities with Vision Zero programs, identifying sites for treatment is critical to achieve the goal of eliminating fatal crashes. A motivation for the analysis could be to identify problems that the community wants to address, for example, improving safety for older or younger pedestrians. Time spent planning can yield more useful results. Just as a skilled carpenter measures twice and cuts once, a safety analyst should plan ahead and make key analysis decisions in order to get the most out of the available data. ![]() Guidebook on Identification of High Pedestrian Crash Locations
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