Application of the AASHTO Highway Safety Manual (HSM) Karen Dixon, Ph.D., P.E. Email: [email protected] 1 HSM Overview 2 Integrate Safety Need into Decision Processes 3 Safety Trade-Offs? Costs Environment Safety Right-of-Way What Do You Do? 4 Highway Safety has Two Dimensions Nominal Substantive Safety Safety Standards Expected or Actual Compliance Crash Frequency and Severity 5 Design Exception Insights Nominal Safety is an ABSOLUTE r e t a e r G K S I R H S Substantive A R Safety is a C CONTINUUM Greater DESIGN DIMENSION 6 HSM Vision Akin to HCM 1 Definitive; represents quantitative ‘state-of-the- art’ information 2 Widely accepted within professional practice of transportation engineering 3 Science-based; updated regularly to reflect research 7 Common Impacts for Project Level Decisions? • Traffic Noise • Traffic • Cost Models Design Models Operations / • Real Estate Criteria • Air Quality Models Microscopic Appraisals (nominal • 3-D Visualization Simulation • DOT e safety) v • Environmental • Construction Databases t i h t a Assessments Plans g t i i e t n The HSM W a u r e Q t Substantive Safety a e e r r o G M Safety Environmental Traffic Right-of-Way Costs Impacts Impacts Operations 8 Design Existing Conditions Alternative 1 Alternative 2 Alternative 3 9 >> 0 >> 1 >> 2 >> 3 >> 4 >> Vol. 1 (Part A) Vol. 3 (Part D) Introduction Crash Modification Human Factors Factors (CMFs) Fundamentals Vol. 1 (Part B) Vol. 2 (Part C) Roadway Safety Management Predictive Method Process 10