Montréal Crossing - The Hazards of Intersections

1. Xing Jian Liu (M3 – McGill University) Dr. David Kaiser (R5 – PHPM) Faculty Supervisor: Dr. Joseph Cox (MScPH Program, McGill University) Montréal Crossing - The Hazards of Intersections

2. Debrief

3. Tell us about your findings! • Did you observe any events? • What risk factors did you identify? • Any interesting interventions that you observed or dreamed up?

4. Key concepts: types of variables • Variable: any characteristic, number, or attribute that can be measured or counted • Numeric variables have values that describe a measurable quantity as a number, like 'how many' or 'how much' • May take any real number value (continuous) or only whole number values (discrete) • The data collected for a numeric variable are quantitative data

5. Key concepts: types of variables • Variable: any characteristic, number, or attribute that can be measured or counted • Categorical variables have values that describe a 'quality' or 'characteristic' of a data unit, like 'what type' or 'which category' • Categories should be mutually exclusive (in one category or in another) and exhaustive (include all possible options) • May have a natural order (ordinal) or not (nominal) • The data collected for a categorical variable are qualitative data

6. Exercise: types of variables • What kinds of data did you collect? • Take 5 minutes to categorize your findings according to the type of variable that you might use to describe them. Source: Australian Bureau of Statistics, 2013

7. Key concepts: measures of occurrence • Incidence • Measure of the speed at which new events arise in a population during a fixed time. Can be expressed either as a proportion or as a rate. • Incidence proportion (risk) = • Incidence rate (person-time rate) = Source: The Association of Faculties of Medicine of Canada (2013), CDC (2013) http://phprimer.afmc.ca/inner/primer_contents

8. Key concepts: measures of occurrence • Prevalence • Measure of disease state • Counts all existing cases in a fixed time period (including those that began before the observation period), divided by the population size. • Influenced by both the incidence and by the duration of the illness. • Point prevalence: prevalence of a disease state at a specific point in time Source: The Association of Faculties of Medicine of Canada (2013), CDC (2013) http://phprimer.afmc.ca/inner/primer_contents

9. Exercise: measures of occurrence • What could you measure with the data you collected? • Take 5 minutes to think about whether your observations could be used to determine incidence proportion, incidence rate, or prevalence of injuries, collisions or near misses • assume that you have data on the number of events if you did not observe any • Are you missing any information?

10. Key concepts: the epidemiological triad Source: The Association of Faculties of Medicine of Canada (2013) http://phprimer.afmc.ca/inner/primer_contents

11. Key concepts: the epidemiological triad Agent = Kinetic Energy Vector = Vehicles Environment = Physical & Sociocultural Host = Pedestrians

12. Key concepts: accident vs. injury • An accident: • Is an unforeseen event • Assumes unpredictability and inability to prevent • An injury event: • Is predictable based on knowledge of its determinants • Can predict number, distribution, and trends on a population level (not necessarily individually) • Appropriately designed preventive interventions can reduce the number of injuries Source: The Association of Faculties of Medicine of Canada (2013) http://phprimer.afmc.ca/inner/primer_contents

13. Key concepts: risk factors • Risk factors for traffic-related injuries include characteristics of: • individuals • sex, age, ethnicity, socio-economic status • vehicles • mass and speed • environments (physical and social) • roadways: e.g., width, number of lanes, speed limit, volume of traffic, etc. • urban design: e.g., mixity of land use (residential, commercial) • public policy: e.g., high-quality public transit, road safety legislation • “culture” : e.g., priority given to pedestrians v. “car culture”

14. Key concepts: risk factors • Risk factors or determinants can be: • non-modifiable • sex, age, genetic profile • modifiable: • personal behaviours • characteristics of vehicles and the roadway environment • Effective public health interventions should preferentially focus on modifiable factors • But, some non-modifiable factors may help orient interventions

15. Exercise: riskfactors • Given the observations you made regarding potential risk factors: Which intersection would you expect to have a higher number of pedestrian injuries? Why?

16. Key concepts: stages of prevention Source: The Association of Faculties of Medicine of Canada (2013) http://phprimer.afmc.ca/inner/primer_contents

17. Key concepts: stages of prevention • Primordial: Promoting a healthy environment in childhood which emphasizes the importance of physical activity so that individuals, once in adulthood, are more likely to choose walking versus driving when going to work. • Primary: Public campaigns promoting drivers to respect pedestrian right-of-way rules. • Secondary: Prompt transportation of injured victims to a trauma center. • Tertiary: Rehabilitation programs for victims of traffic-related injuries

18. Key concepts: intervention strategies • Active interventions • rely on continued compliance from individuals in the target population for their effectiveness • compliance may be poor because of effort, monetary resources and/or time commitment required • therefore, may increase inequalities in health outcomes • may be fairly simple to design and implement • e.g. school-based traffic education programs for young children Source: The Association of Faculties of Medicine of Canada (2013) http://phprimer.afmc.ca/inner/primer_contents

19. Key concepts: intervention strategies • Passive interventions • applied once, often on a population basis • often in the form of laws or regulations, thus may be difficult to implement • once instituted, they protect the entire population, regardless of personal characteristics • have the potential to reduce health inequalities • e.g. installation of speed bumps on residential streets to reduce average vehicle speeds Source: The Association of Faculties of Medicine of Canada (2013) http://phprimer.afmc.ca/inner/primer_contents

20. Key concepts: the Haddon matrix • Developed by Dr. William Haddon Jr. in 1970 • Can be used to identify and categorize factors associated with injury occurrence according to: • time: pre-event, during the event, post-event • components of the epidemiologic triad • Also useful in thinking about potential interventions • different targets (pedestrians, vehicles, environments) • multiple stages of prevention • active & passive strategies • modifiable risk factors

21. Exercise: the Haddon matrix • What types of interventions did you observe? What potential interventions did your team think of? • Take 5 minutes to classify the interventions using a Haddon matrix

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