Montréal Crossing - The Hazards of Intersections

Xing Jian Liu (M3 – McGill University)Dr. David Kaiser (R5 – PHPM)

Faculty Supervisor: Dr. Joseph Cox (MScPH Program, McGill University)

Introduction

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Learning objectives1. Recognize the public health importance and describe the

epidemiology of traffic-related injuries.

2. Have an awareness of current sources of health data regarding traffic-related injuries and recognise the advantages and disadvantages of each of them.

3. Define the concept of risk factor and distinguish between modifiable and non-modifiable risk factors for traffic-related injuries.

4. Describe the concepts of incidence proportion, incidence rate, and prevalence, and understand the data needed to calculate each.

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Learning objectives5. Define the concept of stages of prevention (primary,

secondary and tertiary) at a population level, and formulate preventive measures.

6. Name and describe two common frameworks applied to core public health functions such as health protection and injury prevention.

7. Describe the advantages and disadvantages of active and passive approaches to prevention.

8. Apply the concepts of stages of prevention, active v. passive strategies, and the epidemiologic triad to the classification of potential interventions to reduce traffic-related injuries.

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ScenarioYou are a Health Sciences student at McGill University and you

have just started the academic year. You moved to Montreal for school and you are excited about living in the Belle Province and learning some French. Also, Montreal is an exciting and busy city with lots of options for activities (walking in Mont Royal Park, great nightlife and food, etc.).

You find yourself downtown after going to the bookstore and you are making your way to Ste. Catherine street. You are approaching the intersection of Sherbrooke and Peel streets where you witness a pedestrian halfway into the intersection yelling at a driver in a BMW (usual behaviour for pedestrians and bikers making their way through downtown Montreal). It seems the pedestrian, who looks to be a fellow student, was almost hit while crossing Sherbrooke, going in the same direction that you planned to go.

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ScenarioYou think to yourself, “Wow! That was a close call! That could

have been me!” You also start to wonder…• How often does this type of “close encounter” happen?

• Are a lot of people injured at this intersection?

• Why do these ‘close encounters’ and injuries happen?

• Is this a public health issue, and if it is, is there anything we can do about it?

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Traffic-related injuries: epidemiology• Mortality• 9th leading cause of death worldwide• in Canada, leading cause of mortality in children and adults <35 years of age• annual global mortality projected to increase from 1.3 million in 2004 to 2.4 million in 2030

Sources: WHO (2004), Statistics Canada (2011)

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Traffic-related injuries: epidemiology• Morbidity• 9th leading cause of disability-adjusted life-years (DALY) lost• 20-50 million injuries per year• globally, most occur amongst pedestrians, cyclists or

“motorized 2-wheelers”• in North America, the majority are amongst motor vehicle

occupantsSources: WHO (2004), Statistics Canada (2011)

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Pedestrian injuries: epidemiology• In Canada, 95% occur in an urban

area (1992-2001)• More likely to result in hospitalisation

or death than injuries to motor vehicle occupants

• In Montreal, 1500-1800 traffic-related injuries per year occur among pedestrians• For each recorded injury, there are

many more people with minor injuries or psychological effects due to near misses and perceived lack of safety

Sources: Transport Canada (2004), Direction de santé publique de Montréal (2005)

Source: BC Public Service Agency

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Traffic-related injuries: risk factors• “an aspect of personal behaviour or lifestyle, an environmental exposure, or an inborn or inherited characteristic which on the basis of epidemiological evidence is known to be associated with health-related conditions considered important to prevent.”

• According to this definition, no distinction is made between determinants of health and risk factors

Last, Dictionary of Epidemiology

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Traffic-related injuries: sources of data• Administrative databases• indicator of morbidity: emergency room visits, hospitalisations• pros: easy access, comparable over time, fairly complete for

more severe injuries• cons: misses many minor injuries and property-damage only

(PDO) collisions; no information on circumstances of collision

• Death registries• indicator of mortality• pros: exhaustive (for mortality)• cons: the tip of the iceberg!!

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Traffic-related injuries: sources of data• Insurers (government or private)• indicator of morbidity: collisions involving property damage, injuries

receiving compensation• pros & cons: similar to administrative databases, although events

included will differ

• Police reports & ambulance transports• indicator of morbidity: collisions for which police/ambulance were called• pros: more likely to capture minor injuries and PDO collisions,

circumstances of the collision & precise localisation• cons: don’t capture near-misses, may be less likely to capture cyclist

injuries

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Field exercise: research questionWhat are the observable factors that may influence the occurrence of traffic-related injuries among pedestrians at intersections in downtown Montreal [or another city, if applicable]?

Outcome: Injuries, collisions, and near missesTarget population: Pedestrians crossing intersections in an urban

setting Study population: Pedestrians crossing 2 specific downtown

Montreal [or another city, if applicable] intersectionsSample: Pedestrians crossing 2 specific downtown intersections in

a span of 30 minutes

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Field Exercise: objectives• Observe and record injuries, collisions, and “near

misses”A near miss is an unplanned event that does not result in

injury, e.g., a pedestrian sees a car at the last minute and jumps out of the way

• Observe and record factors that may be associated with the number of traffic-related pedestrian injuries

• Identify actual and potential preventive interventions• Thinking broadly of interventions at multiple levels

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Field Exercise: instructions• Each team will receive a package containing

• Pencil & clipboard• Map of your 2 intersections

• for Montreal intersections:• Team 1: Pine/St-Urbain and Roy/Henri-Julien • Team 2: University/Sherbrooke and Hutchison/Milton• Team 3: Sherbrooke/Peel and Maisonneuve/Mackay

• Tables 1 & 2• While walking there, you should start thinking about:

• things you might want to observe at each intersection• how you will divide up the work• interventions to reduce pedestrian ‘near misses’, collisions & injuries at

intersections• Spend around 30 minutes observing each intersection

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Field Exercise: instructions• Fill out Table 1 with factors that you feel might be

associated with the occurrence of pedestrian injuries at each intersection

• In Table 2:• Note any interventions that you observe and potential

interventions you think might reduce the number of pedestrian injuries at each intersection• Note any injuries, collisions or near misses observed, as well

as the circumstances of these events

• Have one member of the team report back about the team’s findings at the debrief session

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