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10 Overview With consideration of the issues discussed, along with research into the relationships among roadway characteristics including posted speed limit, operating speed, and safety, the research team developed a procedure to calculate a suggested speed limit. The procedure starts with iden- tifying the roadway segment context and type. Next, the speed distribution of drivers on that segment is used to identify a potential suggested speed limit that is adjusted with consideration of the crash potential for the segment. FigureÂ 4 illustrates the steps for the procedure. Additional details are provided in the sections that follow. The suggested speed limit procedure applies to posted speed limits. Procedures for setting school zone, work zone, variable, or advisory speeds are not discussed in this document. Speed Limit Setting Tool The SLS-Tool was developed to facilitate calculating the suggested speed limit. The tool uses spreadsheets to automate the procedure. A copy of the SLS-Tool is available on the TRB website (TRB.org) by searching for âNCHRP Research Report 966.â S E C T I O N 3 Procedure to Calculate the Suggested Speed Limit Calculated value based on consideration of roadway context and type, speed distribution, and safety Consideration of drivers' speed selection on the segment / Consideration of crash risk based on roadway characteristics Context = rural, rural town, suburban, urban, or urban core / Type = freeway, major arterial, minor arterial, collector, or local Roadway Context and Type Speed Distribution Safety Suggested Speed Limit FigureÂ 4. Overview of procedure to calculate suggested speed limit.