Foundations of Road Safety
21%of exam
Safe System & Safety ScienceHaddon Matrix, 4 E's & CostsNominal vs Substantive SafetyKinetic Energy & Speed
Measuring Safety
20%of exam
Safety Databases & Injury ScalesCrash Rates, SPFs, EB & CMFsRegression to the Mean (RTM)Negative Binomial Overdispersion
Human Factors and Road Safety
20%of exam
Driving Task, PRT & ExpectancyVision, Workload, Distraction & UsersPositive Guidance & PrimacyDeterrence & Risk Compensation
Solving Road Safety Problems
24%of exam
HSM 6-Step Safety ManagementProven Countermeasures & VRU ToolsRoadside Hierarchy, RSAs & AppraisalSystemic vs Hot-Spot Screening
Implementing Road Safety Plans and Programs
15%of exam
Quick Facts
- Credential
- Road Safety Professional Level 1
- Administrator
- TPCB via Meazure Learning
- Questions
- 75 qualitative MCQs (no calculations)
- Time Limit
- 3 hours (180 minutes)
- Passing Score
- Criterion-referenced Modified Angoff standard
- Testing Windows
- February, June, and October
- Eligibility
- Bachelor +2 relevant years; otherwise 4
- Renewal Cycle
- 3-year cycle; 24 qualifying PDH
- Ethics From 2027 Cycle
- 1 PDH per three-year cycle
FHWA Five Safe System Elements
Safe Users, Vehicles, Speeds, Roads, and Post-Crash Care
Safe Road UsersSafe Vehicles & SpeedsSafe RoadsPost-Crash Care
Nominal Safety vs Substantive Safety
Nominal Safety
- Meets design standards and manuals
- Compliance does not guarantee low risk
- Can still have high crashes
Substantive Safety
- Actual or expected crash frequency/severity
- Measured along a risk continuum
- Evaluated via SPFs and EB
Code compliance vs real crash risk
Safe System & Safety Science
- Nominal Safety
- Compliance with applicable design requirements
- Substantive Safety
- Actual or expected crash performance
- USDOT Safe System Elements
- Users, Vehicles, Speeds, Roads, Post-Crash5 elements
- Safe System Human Principles
- Unacceptable death/injury; mistakes; human vulnerabilityFHWA: 3 of 6
- Swiss Cheese Model (Reason)
- Layer weaknesses can combine; strengthen redundancy
- Kinetic Energy Law
- KE grows with speed squared1/2 m v^2
- Safe System Management Principles
- Shared responsibility; proactive safety; redundancyFHWA: 3 of 6
Haddon Matrix, 4 E's & Costs
- Haddon Matrix Phases
- Pre-Crash, Crash, and Post-Crash3 rows
- Haddon Matrix Factors
- Human, Vehicle, Physical/Social Environment3 combined or 4 separated
- Traditional 4 E's
- Engineering, Enforcement, Education, EMS
- Expanded Modern E's
- Equity and Evaluation added
- NMVCCS 94% Critical Reason
- Historical driver-critical reason ≠ causation/fault
- Comprehensive Crash Cost
- Economic losses plus quality-of-life valuationAvoid double counting
KABCO Police Injury Scale
K Fatal; A Suspected Serious; B Suspected Minor; C Possible
K: Fatal injuryA: Suspected serious injuryB: Suspected minor injuryC: Possible injuryO: No apparent injury
CMF Clearinghouse vs NHTSA Star Ratings
CMF Clearinghouse Stars
- 1-to-5 study quality rating
- Measures statistical rigor and sample
- Stars do not quantify reduction size
Countermeasures That Work
- NHTSA behavioral safety guide
- 1-to-5 effectiveness star rating
- Measures demonstrated crash/behavior impact
Study quality vs treatment effectiveness
Safety Screening & Evaluation Method Picker
- Short-term high crash count→Check RTM, exposure and model suitability
- Need excess-crash screening measure→Compare EB expected minus SPF predicted
- Severe crashes dispersed across network→Assess systemic risk factors and patterns
- No suitable SPF for evaluation→Consider justified comparison-group design
- Need early mechanism feedback→Use validated conflicts/behavior measures
Safety Databases & Injury Scales
- KABCO Police Scale
- K fatal; A suspected seriousK-A-B-C-O
- AIS Clinical Scale
- Clinical anatomical severity: 1 minor–6 maximal
- FARS (NHTSA)
- Public-trafficway fatal-crash census; 30-day deathDeath <=30d
- CRSS (NHTSA)
- Probability sample of police-reported crashes
- MMUCC & MIRE
- Standard crash and roadway elements
- Six Data Quality Attributes
- Timely, Accurate, Complete, Uniform, Integrated, Accessible
- KABCO B/C/O
- Suspected minor; possible; no apparent injury
Crash Rates, SPFs, EB & CMFs
- Intersection Crash Rate
- Crashes per Million Entering VehiclesMEV
- Segment Crash Rate
- Crashes per 100M Vehicle-Miles TraveledHMVM
- Safety Performance Function (SPF)
- Predicts average crashes for defined facilities
- Regression to the Mean (RTM)
- Extreme random observations tend toward average
- Empirical Bayes (EB) Method
- Weights SPF predicted and observed crashesAddresses RTM bias
- CMF & CRF Formula
- CRF% = (1 − CMF) ×100CMF 0.7 = 30%
PIEV Response Stages
Perceive, interpret, decide, respond; actual time depends on conditions
Perception: detect stimulusInterpretation: recognize significanceDecision: choose responseResponse: initiate physical action
Young Novice vs Older Driver Risks
Young / Novice Drivers
- Immaturity, speeding, peer distraction
- Poor hazard anticipation skills
- Mitigated by GDL nighttime/passenger rules
Older Drivers
- Vision/processing changes vary between individuals
- Complex left-turn gap judgment errors
- Physical fragility can increase injury severity
Inexperience/risk-taking vs fragility/complex gaps
Driving Task, PRT & Expectancy
- Driving Task Hierarchy
- Control, Guidance, then NavigationPrimacy order
- PIEV / PRT Four Stages
- Perception, Intellection, Emotion, Volition
- AASHTO Stopping Design PRT
- 2.5 seconds; design assumption, not guarantee
- A Priori Expectancy
- Long-term habit from driving experience
- Ad Hoc Expectancy
- Short-term expectation along current corridor
- MUTCD Clearance-Time Guidance
- 3.5 ft/s; consider slower usersPed clearance
- MUTCD WALK Plus Clearance
- Separate total-time check: 3 ft/sDifferent starting point
Vision, Workload, Distraction & Users
- Foveal vs Peripheral Vision
- Foveal reads detail; peripheral spots motion
- Contrast Sensitivity
- Distinguishing hazards from dark background
- Mental Workload Curve
- Underload and overload can impair performance
- Three Distraction Types
- Visual, Manual, and Cognitive attention
- Deterrence Theory Key Driver
- Certainty, swiftness and severity all matter
- Self-Explaining Roads
- Consistent geometry communicates intended road function
AASHTO 6-Step Roadside Hierarchy
Remove, Redesign, Relocate, Breakaway, Shield, then Delineate
1-3: Remove, Redesign, Relocate4: Reduce (breakaway)5: Shield (barrier/cushion)6: Delineate hazard
Hot-Spot vs Systemic Safety Approach
Hot-Spot Approach
- Reactive to historical crash clusters
- Treats individual high-crash locations
- Screening result requires further diagnosis
Systemic Approach
- Proactive network-wide risk-factor screening
- Deploys widespread low-cost countermeasures
- May include sites without recent crashes
Site crash history vs network risk
Countermeasure Candidates, Not Automatic Prescriptions
- Severe intersection angle crashes→Evaluate roundabout feasibility and safety
- Four-lane undivided corridor conflicts→Evaluate road-diet operations and safety
- Turning traffic conflicts with pedestrians→Consider LPI and complementary protections
- Wide/high-speed uncontrolled pedestrian crossing→Evaluate appropriate crossing control and warrants
- Considering multiple countermeasures→Check compatibility, evidence and overlapping effects
HSM 6-Step Safety Management
- Step 1: Network Screening
- Identify sites with reduction potential
- Step 2: Diagnosis
- Collision and condition diagram analysis
- Step 3: Select Countermeasures
- Match proven treatments to causes
- Step 4: Economic Appraisal
- Compare present-value benefits and costs
- Step 5: Prioritize Projects
- Optimize selection within budget limits
- Step 6: Effectiveness Evaluation
- Assess outcomes with suitable bias controls
Collision Diagram vs Condition Diagram
Collision Diagram
- Schematic arrows of crash maneuvers
- Shows severity, time, surface condition
- Reveals recurring crash-type clusters
Condition Diagram
- Scale map of physical site
- Shows lanes, grades, signs, sightlines
- Links physical features to crashes
Crash patterns vs physical layout
Roadside Risk Treatment Sequence
- Fixed object poses roadside risk→Assess removal or traversable redesign first
- Removal/redesign infeasible→Assess relocation beyond likely encroachment
- Necessary support remains near traffic→Evaluate appropriate crashworthy breakaway design
- Residual hazard merits shielding→Compare barrier risk and available deflection
Proven Countermeasures & VRU Tools
- Roundabouts
- Lower speeds; fewer severe crossing conflictsContext-specific effects
- Road Diet (4-to-3 Conversion)
- Separate left turns; assess conversion feasibility
- Leading Pedestrian Interval (LPI)
- Typically 3–7-second pedestrian head start
- RRFB vs PHB (HAWK)
- Flashing yield beacon vs red stop
- Multiplying Multiple CMFs
- Multiply only with justified independence
- Surrogate Safety Measures
- TTC, PET, speeds, yielding rates
Roadside Hierarchy, RSAs & Appraisal
- Roadside Hierarchy (Top 3)
- Remove, Redesign traversable, Relocate obstacle
- Roadside Hierarchy (Bottom 3)
- Breakaway, Shield with barrier, Delineate
- Recoverable Foreslope
- Generally 1V:4H or flatter
- Road Safety Audit (RSA)
- Independent multidisciplinary review; documented owner response
- Benefit-Cost Ratio (BCR)
- PV benefits / PV costs; >1 net-beneficial
- Mutually Exclusive Alternatives
- Compare using NPV or incremental BCR
- Critical Foreslope
- Steeper than 1V:3H; surface matters
FHWA HSIP vs NHTSA Section 402/405
FHWA HSIP (23 USC 148)
- Managed by State DOTs
- Funds infrastructure on public roads
- SHSP updated within five years
NHTSA Sec 402 / 405
- Managed by State Highway Safety Offices
- Funds behavioral HVE and education
- Guided by Highway Safety Plan
Infrastructure engineering vs behavioral grants
Safety Plan & Funding Stream Picker
- Statewide multidisciplinary safety priorities→Develop SHSP with required stakeholder consultation
- Eligible data-supported public-road safety improvement→Consider HSIP under current funding rules
- Behavioral enforcement/occupant protection program→Check Section 402/405 program eligibility
- Dispersed local network risk→Develop local safety priorities and actions
SHSP, HSIP, NHTSA & PM1
- SHSP Update: 23 CFR 924.9
- Within 5 years of previous approval
- HSIP Scope
- Covers ALL public roads statewide
- NHTSA Sec 402 & 405
- Fund behavioral grants via SHSO/HSP
- PM1 Counts and Rates
- Fatalities/serious injuries: counts and rates
- Complete Streets Policy
- Routine design considers all road users
- Traffic Safety Culture
- Internal agency + external public norms
- PM1 Time Basis
- Five-year rolling average for each measure
- PM1 Non-Motorized Combined Count
- Fatalities plus serious injuries; not rate
Common Traps
Critical Reason vs Causation
94% driver-critical reason ≠ sole causation ≠ Last event ≠ complete causal chain
CMF Quality vs Effect Size
CMF study-quality stars ≠ reduction percentage ≠ High confidence ≠ largest treatment benefit
Before–After Counts vs Causal Effect
Crash decline ≠ proven treatment effect ≠ EB adjustment ≠ universal confounding cure
Zero Crashes vs Safe Access
Zero crashes ≠ proven safe crossing ≠ Suppressed walking ≠ absent pedestrian demand
HSIP Scope vs State Ownership
Public roads ≠ state-owned highways only ≠ Local ownership ≠ automatic HSIP ineligibility
Barrier vs Harmless Protection
Barrier shielding ≠ hazard-free roadside ≠ Hazard delineation ≠ hazard removal
Last Minute
- 1.RSP1: 75 qualitative items; 3 hours
- 2.Level 1 requires no computations
- 3.Solving Problems domain: 24%
- 4.Nominal: compliance; substantive: crash performance
- 5.Haddon: phases × contributing-factor categories
- 6.EB combines observed and predicted crashes
- 7.CMF 0.70 implies 30% reduction
- 8.CMF stars indicate study quality
- 9.Stopping PRT design assumption: 2.5 seconds
- 10.Clearance guidance: 3.5 ft/s
- 11.Routine slower users: consider lower speed
- 12.WALK+clearance: separate 3-ft/s check
- 13.Control precedes guidance and navigation
- 14.RSA process includes written owner response
- 15.HSIP scope includes all public roads
- 16.SHSP update: ≤5 years from approval
- 17.PM1 uses five-year rolling averages
- 18.Renewal: 24 PDH per three-year cycle
- 19.2027 cycles require one ethics PDH
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