A METHOD TO ASSESS COMPETING RISKS ASSOCIATED WITH PEDESTRIANORIENTED ENVIRONMENTS

1
A METHOD TO ASSESS COMPETING RISKS ASSOCIATED
WITH PEDESTRIAN-ORIENTED ENVIRONMENTS Audrey de
Nazelle and Douglas Crawford-Brown Department of
Environmental Sciences and Engineering, School of
Public Health, and Carolina Environmental
Program, The University of North Carolina at
Chapel Hill Contact Campus Box 7431, UNC Chapel
Hill, Chapel Hill NC 27599, audrey_at_unc.edu, 919
966 7238
METHODS
BACKGROUND
PRELIMINARY RESULTS
Creating more pedestrian-friendly environments is
seen as a common cause solution for a multitude
of health and environmental problems that have
challenged US policy makers, such as air
pollution, physical activity, and social
interaction. However, some unintended
consequences may emerge from such community
designs. OBJECTIVE This research aims at
estimating tradeoffs between competing health
risks and benefits physical activity, and
exposures to air pollution and traffic hazards.
Probabilistic model of individual behavior and
exposure to air pollution and traffic hazards

• Use an activity database for daily activity
  patterns
• Simulate individuals choice of destinations and
  travel mode choice in a built environment
  scenario
• Simulate air pollution concentration field in
  time and space
• Combine activity and air pollution data
• Repeat for a different built environment scenario
• Estimate change in traffic injury, air pollution,
  and physical activity health effects
• Combine disparate health effects using a
  quality-adjusted life years method
• Run a Monte Carlo simulation for uncertainty and
  variability analysis

Madison, WI, Photo Michael King
Results of the two-step Monte Carlo process
variability distribution of the mean difference
in individuals energy expenditure (left) and
mean percent increase in ozone inhalation dose
(right) due to the built environment
transformations towards more pedestrian-friendly
design. The mean of the mean difference in energy
expenditure is 12.3 kcal/day the mean of the
mean ozone inhalation increase is 1.9.
Features of pedestrian-oriented built
environments are shown to increase physical
activity for transportation or leisure,
including compact and mixed land uses,
sidewalks, bicycle facilities, access to parks
and trails, and well connected streets
PEDESTRIAN-ORIENTED ENVIRONMENTS DEFINED
CONCLUSIONS

• Decision-makers should assess and address
  potential unintended consequences of creating
  more pedestrian-friendly built environments in
  certain communities.
• The risk assessment approach proposed is an
  appropriate methodology to assess the competing
  risks, particularly because of its ability to
  track uncertainty rigorously.
• Future work needs to consider the many other
  benefits for a fair appraisal of the value of
  pedestrian-oriented environments.

Example of a modeled individual profile of daily
energy expenditure (left) and pollutant
cumulative exposure (inhalation dose) (right).
Red diamonds indicate times of travel.
Increased in-street physical activity may
increase risks due to air pollution exposure
people walking or biking may be spending more
time in more polluted environments and with a
higher inhalation rate than if they were driving.
Society
Nîmes, France, photo by David McNelis

• Principles of pedestrian-friendly environments
  include creating accessible destinations and
  human scale designs, through
• Density (compact land uses)
• Diversity (Land use mix)
• Design (connected streets, grid-like pattern,
  small block sizes, continuous sidewalks,
  landscaping, pedestrian and bicycle amenities,
  etc.)

Miami Beach, FL, photo by Dan Burden
Built Environment
Behavior
Natural Environment
Increasing walking, cycling, or jogging in
streets may increase the risk of traffic death or
injury. In the US traffic mortality per mile
traveled is 23 times higher for pedestrians than
car drivers, for cyclists 12 times.
Example of exposure to ozone during a trip from
home to go shopping at 4PM. The model first
estimates location choice, then mode choice, and
combines activity rate data with the air
pollution field at the time of day the activity
takes place
Health Quality of Life