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Scottsdale commission hears safety‑plan data tying higher speeds to more serious crashes, debates enforcement and prioritization
Summary
Consultants told the Transportation Commission that aggregated 80th‑percentile speeds around 45–50 mph correlate with concentrations of serious and fatal crashes; commissioners debated stricter design standards, automated enforcement and how to prioritize a high‑injury network, and asked staff to return with refined methodology and public questionnaire results.
Scottsdale’s Transportation Commission on Aug. 21 reviewed an initial draft of a Strategic Transportation Safety Plan that links higher localized driving speeds to a greater concentration of fatal and serious‑injury (KSI) crashes and lays out options for how the city will prioritize safety investments.
Consultants from TYLinn, working with Northern Arizona University and using ADOT crash records and Replica connected‑vehicle speed data for 2019–2023, said the city‑only analysis (state routes excluded) shows a concentration of serious crashes where 80th‑percentile speeds cluster around 45–50 mph. “We are seeing a strong correlation…at the 45 to 50 mile per hour 80th percentile,” the presenter said, urging that speed limits be set with crash history and vulnerable‑user exposure in mind, not solely by the 80th‑percentile metric.
Why it matters: Higher operating speeds raise both the frequency and severity of crashes, county‑level and municipal planning decisions can alter street typology and thereby reduce exposure of pedestrians and cyclists. Commissioners framed that technical finding in local terms, pointing to downtown and Old Town as areas of concentrated risk for people walking at night.
Design, enforcement and public perception: Commissioners debated whether to rely primarily on design changes (‘forgiving’ streets) or on enforcement and education. Vice Chair Wilcoxon urged higher minimum design standards, saying design drives behavior and that Scottsdale should “push the bar a little bit higher” rather than ceding control to driver behavior. Consultant materials also flagged automated/photo enforcement as an increasingly affordable tool; the presenter cited a regional example in which “nearly 10,000 violations [were] under review with over 2,200 citations…in just a two‑week period,” and warned that public messaging must avoid the perception that enforcement is a revenue‑raising exercise.
Prioritization and targets: Staff proposed a two‑tier prioritization approach — a high‑injury network (HIN) focusing on arterial segments for capital investment and a neighborhood tier driven by local priorities and traffic calming. Commissioners debated goal horizons for reducing KSI crashes (10, 15 or 20 years, and aspirational targets). Wilcoxon offered an aspirational target: “100% by 2050,” while other members favored shorter, measurable targets tied to the Transportation Action Plan and capital‑improvement cycles.
High‑injury‑network methodology options: Consultants presented four HIN ranking methods: (1) frequency (total KSI), (2) rate (KSI normalized by traffic volume and segment length), (3) an EPDO‑style weighted method that scales more severe crashes (AASHTO weights: 25 for fatal, 10 for A, 1 for B/C/O) combined with a rate component, and (4) ranking by ADOT’s state‑adjusted crash monetary costs (consultant gave current ADOT values for reference). Commissioners generally favored option 3 with amendments to exclude extremely low‑volume locations that can artificially spike rates; several asked for a separate vulnerable‑road‑user (pedestrian/bicycle) HIN as well.
What the commission asked next: The commission did not take a final vote on methodology but requested that consultants return with: (a) refined examples of option 3 that filter out low‑volume anomalies, (b) a layperson‑friendly explanation for public communications, (c) separate VRU analyses, and (d) a public questionnaire incorporating aspirational vs. pragmatic goal options.
A direct quote capturing public messaging concerns came from the consultant: “These perceptions are real in the public, and the culture that you around safety is a real consideration,” underscoring the need for clear, data‑driven outreach.
What’s next: Consultants will produce a first draft of goals and a prioritized HIN using the commission’s guidance, include societal crash‑cost figures for context, and return with concrete options for a future meeting and the public questionnaire results. The consultant also flagged an education/enforcement/emergency‑responder item planned for the Sept. 18 meeting.
Sources and attribution: The article draws on the Aug. 21, 2025 Transportation Commission meeting presentation and exchanges. Quotes and specific claims are attributed to commissioners and presenters appearing in the commission transcript, including Vice Chair Wilcoxon and TYLinn consultant Ryan.
