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                        Methods and Practices for Setting Speed Limits: An Informational Report


            
            In This Section
        Speed Management Safety
                USLIMITS2
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                Summary of Results
Table 17 shows the recommended speed limits yielded by each speed limit setting method and the actual speed limit enacted by the road authority for both case studies are shown below.

**Table 17. Recommended Speed Limits for the Case Studies**

**Eldron Boulevard, Florida**
			**State Route 67, California**Actual Speed Limit
			40
			55Illinois DOT
			40
			55Northwestern
			45
			55USLIMITS2
			40
			55Optimal Speed
			45
			50Safe System Speed
			30
			50With the exception of the safe systems approach, the recommended speed limit from each of the methodologies used are within 5 mph of each other. On the one hand, this suggests an inter-method consistency that is reassuring. However, it needs to be remembered that these are only two specific examples, and this consistency may not endure in other cases. In fact, the optimal speed and the safe systems approaches are known to produce results that have a more pronounced difference from the other methods in certain situations. This is perhaps not surprising since the Illinois DOT method, the Northwestern method, and USLIMITS2 all start from the 85th percentile speed.

As expected, the safe speed approach resulted in speed limits that are at the low end of the range. This becomes very apparent in the urban case on Eldron Avenue, where the potential for more frequent right-angle crashes requires a more dramatic decrease in operating speeds to be consistent with the zero tolerance for injury-producing crashes.
      
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                Book:Methods and Practices for Setting Speed Limits: An Informational Report
              Background
                Purpose & Scope
                Report Organization
                The Safety of Speed
                Speed Limit Basics
                Speed Limit Sign and Placement
                Speed Study Data Collection
                Speed Limit Enforcement
                Case Studies
                Summary of Results
                References
                Appendix A: Glossary
                Appendix B: Example Traffic Control Order
                Appendix C: Illinois Policy on Setting Speed Limits
                Appendix D: Northwestern Speed Zoning Technique
                Appendix E: Speed Limits New Zealand (Road Risk Methodology) U.S. DEPARTMENT OF TRANSPORTATION

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