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Introduction to Transportation Safety


Exposure: a key concept for understanding transportation safety ... Analyzing safety: key data sources and methods ... aimed at improving safety were initiated: ... – PowerPoint PPT presentation

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Title: Introduction to Transportation Safety

Introduction to Transportation Safety
  • CRP 445/545
  • September 2007

Outline for Today
  • The scale of the transportation safety issue
  • Compared to what? Accidental death statistics
  • Exposure a key concept for understanding
    transportation safety
  • Transportation safety trends over time
  • A very brief history of transportation safety
  • The three rings of safety
  • Operators (human factors)
  • Guideways (roads, airways and airports,
    waterways, railroads) and the Environment
    (weather and other natural phenomena)
  • Vehicles (cars, trucks, buses, aircraft, trains,
  • Analyzing safety key data sources and methods
  • The quasi-random nature of fatal transportation
  • Whos involved in making transportation safer?

Outcomes The Scale of the Transportation Safety
  • Transportation accidents account for more deaths
    than all natural disasters combined
  • Your odds of dying in a transportation accident
    in any given year are about 1 in 6000
  • Your odds of dying in a transportation accident
    in your lifetime are about 1 in 80, assuming a 75
    year lifespan
  • Your odds of being injured in a transportation
    accident are better than 1 in 1000 in any given

Long-Term Safety Trend
  • These statistics are a bit old
  • But guess what? They havent changed that much in
    recent years
  • We have hit a plateau in transportation safety
  • Fatality rate is now pretty constant
  • As travel goes up, fatalities will start to rise

The Fatalities Plateau
Fatality Rate vs. Injury Rate
Why the difference in trends? Any thoughts?
Over Half of Accidental Deaths Involve
Transportation is the Dominant Cause of
Accidental Deaths
Transportation Deaths Compared to Other Causes of
Death from Injuries
Outcomes The Cost of the Transportation Safety
  • Improving transportation safety has major
    economic implications
  • Motor vehicle crashes are the leading cause of
    death in the US for persons aged 5 through 27
  • Huge loss in future economic production
  • The direct cost of crashes to the economy is
    about 150 - 200 billion/year
  • (Estimate is a bit old, should be higher now)
  • Lost productivity, health care, property losses,
  • About 1 ½ to 2 of the entire 1 trillion US
    economy represents losses from transportation
  • About 40,000 fatalities, 5.2 million other
    injuries, and 27 million damaged vehicles

A Brief History of Transportation Safety Policies
  • There was surprisingly little interest in US
    transportation safety issues until the 1960s.
  • Most effort before 1960 went into improving the
    safety of vehicles, e.g. better tires and brakes
  • At that point in time many policies aimed at
    improving safety were initiated
  • Investigations of major airline crashes (NTSB)
  • Motor vehicle safety standards (e.g. seat belts
    and mandatory crash testing) and tire grading
    standards (NHTSA)
  • Major reviews/research into highway geometric
  • Tougher standards for commercial trucks and
    drivers (USDOT)
  • Since the 1960s safety has improved tremendously
    when increased exposure is taken into account

What Is Exposure?
  • In order to make reasonable comparisons of
    relative safety among trips and modes,
    adjustments for exposure are necessary
  • Exposure is usually a function of miles traveled
    or trips made
  • Passenger-miles, vehicle-miles, passenger trips,
    flights, etc.
  • Fatality rate fatalities / exposure
  • Risk f (exposure, fatality or crash rate)
  • How much exposure to transportation risk do you
    have in a month?

Example Urban Transportation Fatality Rates for a
Rates for modes with small exposure (e.g. light
rail) will tend to be very volatile. One event c
an dramatically change the fatality rate.
Selected Intercity Transportation Fatality Rates
for a Year
Rates for modes with small exposure (e.g.
intercity rail and commuter airlines) will tend
to be very volatile. Why do you think the number
for rail is so high? Why is the number for
commuter airline so low?
A Fundamental Shift In Automobile Transportation
In Iowa, there are now more vehicles than driver
NTPS is the National Personal Transportation
Airline Activity Increased Very Rapidly Much
More Exposure
Activity declined after 9/11, but recovering ba
ck to trend
Airline Fatality Rates Fluctuate But Have Trended
Exposure Has Dramatically Increased Since The
1920s Deaths Adjusted For Exposure Are
Dramatically Lower
Highway Death Rates Adjusted for Exposure Have
Been Were Almost In Half After 1965 Why?
Crash Rates Exhibit Considerable Variation
  • Males are twice as likely to die in a
    transportation accident than females
  • A product of higher exposure AND a higher rate of
    involvement in crashes
  • Want to comment on this?
  • The risk of dying in a transportation accident
    varies tremendously from place to place
  • Six times as high in Wyoming (39 deaths per
    100,000 persons) as in Massachusetts (7)
  • Iowa (17), Illinois (12), Minnesota (13),
    Missouri (20), Nebraska (18), South Dakota (20),
    Wisconsin (14)
  • Why do you think there is a large variation?

Men Travel More Person-Miles Than Women More
Possible Sources of Variation?
Crash Rates Exhibit Considerable Variation
  • Crash rates can vary considerably from year to
    year, especially on individual system links
  • In Iowa, nearly half of all crashes occur during
    the winter months in inclement weather as drivers
    fail to adapt to poor road surface conditions
  • Crashes and crash rates vary by time of the year
    (due to weather) and time of day (due to
    visibility and presence/absence of drunk
  • Many fatal crashes occur at night and on weekends

What Causes Highway Crashes? The Haddon Diagram
  • Over 1/3 of crashes involve
  • more than one primary
  • cause
  • Driver error or impairment is by far the greatest
    cause of
  • crashes
  • Driver/roadway/environment
  • interactions are very significant
  • in generating crashes
  • Vehicle problems
  • are the least common cause of crashes

An Indication of the Importance of Human
Factors Driver Risk Varies Dramatically By Age
Risk adjusted for exposure e.g. miles driven.
What Causes Accidents For Other Modes? Airlines…
  • Causation statistics for other modes (e.g.
    railroads, maritime transport, and aviation) are
  • For instance, most major airline crashes have
    been determined by NTSB to result from pilot
    error or other human factors (maintenance or
    design errors), weather conditions, or a
    combination of the two
  • Controlled flight into terrain (CFIT)
  • Loss of control in flight
  • Mid-air collision
  • Crash on landing

Human Factors Cause Most Airline Crashes and
Three Types of Safety Strategies
  • Crash prevention (before the crash)
  • Crash injury and fatality mitigation (during the
  • Improving emergency response and medicine (after
    the crash)

Some Crash Prevention Strategies
  • Commercial driver testing and licensing
  • Drunk driving limits and enforcement
  • Speed limits and speed limit enforcement
  • Standardization of traffic control devices
  • Improvement of roadway geometric designs
  • Managing direct access to land from arterial
  • Aircraft safety regulation and inspection
  • Post-crash investigations and analysis of crash
    data (e.g. IHSDS in Iowa, FARS, and NTSB at
    Federal level)
  • Camera enforcement of speed and red light
  • Road condition and weather information (e.g.

Some Mitigation Strategies Reduce The
Consequences of Crashes
  • Wider roadway clear zones
  • Ditch slope standards
  • Improved roadway medians
  • Crash testing of vehicles and roadside hardware
  • Automobile safety feature requirements (e.g. seat
    belts, air bags, tire grading, stability
  • Flammability standards for materials used in
    aircraft cabins and inside automobiles
  • Improved guard rails and breakaway posts

Emergency Response Strategies
  • Improved crash fire and rescue capabilities at
  • Training and certification of emergency medical
  • Enhanced 911 systems (E-911)
  • Video surveillance of high crash locations
  • Pre-positioning of emergency response vehicles
  • Mayday systems on motor vehicles

Many Actors Are Involved in Transportation Safety
  • Federal agencies US DOT (FHWA, NHTSA, NTSB)
  • State agencies (DPS, DOT)
  • Local agencies (roads and streets, police)
  • Private sector (insurance companies, trade
    organizations like Insurance Institute for
    Highway Safety, motor vehicle manufacturers, K-12
    schools, trucking companies, aircraft
    manufacturers, airlines)

Primary Safety Data Sources
  • FARS
  • Police report data
  • Iowa example ALAS
  • NTSB investigations

Fatality Analysis Reporting System (FARS)
  • Compiled by the US Department of Transportation,
    National Highway Traffic Safety Administration
  • Contains about 37,000 records per year of fatal
    highway crashes in all 50 states
  • Can be queried on-line at http//www-fars.nhtsa.d
  • Useful for understanding causes of fatal crashes,
    however not a geospatial database

Sample National Statistics From FARS
Police Accident Report Databases Iowas Crash
  • Iowa is one of several states that has
    computerized its police crash report data
  • About 70,000 records per year are available in
    either Microsoft Access database or ESRI ArcView
    Geographic Information System (GIS) format
  • A geospatial databasecan be used to develop
    complex queries and maps

Mapping Ice and Snow-Related Crashes With GIS
These maps helped identify a roadway icing probl
em on I-380 in Cedar Rapids
NTSB Investigation Results
  • The National Transportation Safety Board (NTSB)
    is an independent Federal agency that
    investigates major, fatal transportation
    accidents with interdisciplinary teams
  • Aviation, maritime, motor carrier, intercity bus,
    school bus, and pipeline (concentrates heavily on
  • Examples TWA flight 800 explosion, ValueJet
    Everglades crash, Alaska Air crash, JFK Jr., USS
    Greenville/Ehime Maru sinking, Payne Stewart
    crash, major railroad crashes (hazmat, school
  • Investigation results and recommendations are
    released to the public
  • Companies and agencies generally comply with

Fatal Crashes Are Fairly Random Events
  • They often have multiple or unusual causes
  • For instance
  • A driver with a heart condition is driving a
    large commercial vehicle with poor brakes during
    morning rush hour, has a heart attack and crosses
    a grass median into opposing traffic
  • Two experienced commercial pilots fail to look up
    a navigation code in a long list, guess at the
    code, enter the wrong code into a computer and
    the autopilot flies the plane into a mountainside
    at night (American Airlines crash in Columbia,
    South America)

A Fatal Crash What Was the Cause?
Injury Accidents Show Spatial Patterns, Fatal
Crashes Usually Do Not (They Are Rare And To Some
Extent Random Events)
  • One implication of this
  • Chasing fatalities can be an expensive and
    futile activity
  • Next years fatal crash location will probably be
    different than this years
  • Highway safety engineers will instead tend to
    identify high crash rate locations based on
    serious injury crashes rather than fatalities
  • Fatal crashes may be counted as injury crashes
  • More data means more reliability

Next Three Classes
  • Improving vehicle safety focus on motor
  • Discussion what features could you
    change/add/eliminate to make motor vehicles
  • Improving the safety of guideways focus on
    highways, airways, and weather
  • What features of guideways could be changed to
    improve safety?
  • Improving operator safety focus on drivers,
    commercial vehicle operators, and pilots
  • What are some key human factors issues and how
    can they be addressed?
  • Safety data and analysis tools
  • Discussion your short papers on safety

Discussion Transportation Safety
  • Small group discussion
  • Have you been involved in a traffic crash where
    there were injuries?
  • What were the causes?
  • What can you personally do to make transportation
    safer for your self, your family, and your
  • Think exposure
  • Vehicle considerations
  • Guideway and weather considerations
  • Driver behavior