Past projects

Yiannakoulias N, Bland W, Scott DM. A geography of moral hazard: sources and sinks of motor-vehicle commuting externalities.  Health & Place 2014; 29:161-170.

Motor-vehicles are responsible for harms to health that are not directly experienced by individual drivers – such as air pollution and risk of injury to pedestrians. In addition to their direct effects on health, these harms also represent a moral hazard since drivers are not required to consider their effects as part of their decision to drive. We describe an approach for estimating sources of motor-vehicle commuter externalities as a means of understanding the geography of moral hazard, and in particular, the spatial displacement of negative health externalities associated with motor-vehicle commuting. This approach models motor-vehicle commuter traffic flow by trip origin for small geographic areas within the City of Toronto, Ontario. We find that most health-related externalities associated with motor-vehicle commuters are not locally generated, with a large share coming from outside Toronto. Low income is associated with externalities originating outside the municipal boundary, but not with locally sourced externalities. We discuss the impact of geographical moral hazard on the agency of citizens as well as policy options aimed at addressing motor-vehicle externalities.

Yiannakoulias N, Bland W, Scott DM.  Altering school attendance times to prevent child pedestrian injuries.  Traffic Injury Prevention 2013; 14:1-10.

The purpose of this research was to determine whether modifying school start time schedules can be used to reduce children’s exposure to traffic on their morning walks to school.  We use models of pedestrian and motor vehicle commuting to estimate the frequency of encounters between child pedestrians and motor vehicles at intersections throughout the City of Hamilton, Ontario, Canada. We use a simple heuristic to identify the school-specific start times that would most reduce the local frequency of encounters between motor vehicles and pedestrians.  Our analysis suggests that it may be possible to achieve an almost 15 percent reduction in the total number of encounters between childpedestrians and motor vehicles during the morning commute by staggering school start times such that the periods of high pedestrian activity are temporally staggered from periods of high motor vehicle activity. Our analysis suggests that small changes in school start times could be sufficient to see noteworthy reductions in pedestrian exposure to traffic.  Changing school times may be an effective, inexpensive, and practical tool for reducing child pedestrian injuries in urban environments. Enhanced transportation models and community-based interventions are natural next steps for exploring the use of school-specific scheduling to reduce the risk of child pedestrian injury. Further research is required to validate our models before this analysis should be used by policy makers.

Yiannakoulias N, Scott DM.  The effects of local and non-local traffic on child pedestrian safety: a spatial displacement of risk.  Social Science & Medicine 2013; 80:96-104.

In most places, motor-vehicle traffic volume is associated with increased risk of child pedestrian injury; however, the burden of risk is geographically complex. In some neighbourhoods, proportionally fewer drivers may be local, meaning that the moral and practical responsibility of risk to children is displaced from one place (e.g., the suburbs) to another (e.g., downtown). Using the City of Toronto, Canada, as a case study, this research asks two related questions: 1) what is the variation in traffic volume by neighbourhood of origin and socioeconomic status and 2) what is the relationship between the geographical origin of traffic and the risk of collisions involving child pedestrians and motor-vehicles? We find that low-income downtown neighbourhoods have the highest proportion of non-local traffic. We also find that while higher local traffic activity is associated with lower risk of collision, higher flow-through traffic activity (excluding traffic from major thoroughfares) is associated with higher risk of collision. We interpret the former as very likely a proxy of parents’ frequency of chauffeuring children to school, and the latter an illustration of the spatial displacement of riskbetween Toronto neighbourhoods. Our results suggest that more attention needs to be paid to account for the externalization of harm experienced by children, particularly in low-income downtown neighbourhoods.

Yiannakoulias N, Bland W, Svenson LW.  Estimating the effect of turn penalties and traffic congestion on measuring intra-urban accessibility to primary health care.  Applied Geography 2013; 39:172-182.

Geographic variations in spatial accessibility to public resources, such as health care services, raise important questions about the efficiencies and inequities of the processes that determine where these services are located. Spatial accessibility can be measured many different ways, but many of methods in use today involve some measure of travel cost (in time or distance). In this study we explore a simple methodological question: how much are models of spatial accessibility influenced by the precise metric of travel cost? We address this question by comparing spatial accessibility to primary care physicians for two different methods of calculating travel cost (in time) on a street network: free-flow travel time and congested with turn penalties travel timedwhich augments free-flow travel times with the burden of traffic congestion and traffic intersection controls. We consider the effect of these two metrics of travel cost on a gravity-based measure of spatial accessibility to primary health care services in Edmonton, Alberta, Canada. Our results suggest that while travel times between locations of demand and locations of primary care providers greatly differ based on how travel cost is calculated, the gravity-based measure of spatial accessibility provides similar information for both travel cost metrics. Using congested with turn penalties travel time can be an onerous addition to the analysis of spatial accessibility, and is more useful for measuring absolute travel time rather than modeling relative spatial accessibility

Yiannakoulias N, Bland W. A spatial scan approach to detecting focused-global clustering in case-control data.  Geographical Analysis 2012; 44:368-385.

Clustering of spatial event data around points of interest (such as point-emitting sources of pollution) can indicate a relationship between the probability of the event’s occurrence and the distance from those points of interest. Several focused cluster detection methods have been developed to identify such clustering when it occurs. We present a focused spatial scan cluster detection method for detecting clustering of cases around points of interest in case-control data. This method has more power to detect clustering than the traditional focused spatial scan method and requires less parameterization than many other alternatives. We test this method with synthetic hot spot and clinal cluster data, and then with real-world data for motor vehicle collisions involving child pedestrians in Toronto, Canada. The method performs reasonably well in comparison with other methods, provides descriptive information about the range of clustering around points of interest, and does not require corrections for multiple testing. Future work will incorporate this approach with methods that search for clusters in non-circular shapes—such as along water drainage basins and road networks.

Bennet S, Yiannakoulias N, Williams AM, Kitchen P.  Playground accessibility and neighbourhood social interaction among parents.  Social Indicators Research.  2012; 108:199-213.

While the positive association between social interaction and access to green space is well accepted, little research has sought to understand the role of children’s playgrounds in facilitating social interaction within a community. Playgrounds are spaces designed to facilitate play and the interaction of children, but may also be important places of interaction between parents. In this paper we examine how access to playground spaces is related to social interaction between parents. We use two measures of accessibility (1) walking distance to the closest playground and (2) playground service area, a measure of the number of potential users of a playground based on population density. We use generalized estimating equations, an extension of generalized linear models, to control for the confounding effects of socio-economic status (income, education), neighbourhood dynamics (neighbourhood location, years in neighbourhood) and free time (daily outdoor activity, marital status, number of children) on the independent relationship between social interaction and access to playground spaces. Our results suggest that while accessibility to playgrounds is associated with social interaction among parents, the direction of the effect is opposite to existing literature on green space and social interaction; parents with low accessibility to playgrounds are more likely to interact socially with their neighbours than parents with high accessibility. Our results suggest a pattern of spatial behaviour in which the burden of poor access to some resources may actually encourage greater neighbourhood engagement. Future research studying the relationship between health and green space may benefit from studying the specific role of playground spaces

Yiannakoulias N, Bennet S, Scott DM.  Mapping commuter cycling risk in urban areas.  Accident Analysis & Prevention 2012; 45:164-172.

Cycling is becoming an increasingly important transportation option for commuters. Cycling offers exercise opportunities and reduces the burden of motor vehicle travel on society. Mapping the risk of collision between cyclists and motor vehicles in urban areas is important to understanding safe cyclist route opportunities, making informed transportation planning decisions, and exploring patterns of injury epidemiology. To date, many geographic analyses and representations of cyclist risk have not taken the concept of exposure into account. Instead, risk is either expressed as a rate per capita, or as a count of events. Using data associated with the City of Hamilton, Canada, we illustrate a method for mapping commuter cyclist collision risk per distance travelled. This measure can be used to more realistically represent the underlying geography of cycling risk, and provide more geographically and empirically meaningful information to those interested in understanding how cycling safety varies over space.

Yiannakoulias N.  Spatial aberration vs. geographical substance: representing place in public health surveillance.  Health & Place.  2011; 17:1242-1248.

Public health surveillance involves the routine and ongoing collection, analysis and dissemination of health information for a variety of stakeholders-including both public health officials and the public. Much of the current focus of public health surveillance is on detecting aberrations in space-largely inspired by concerns about bioterrorism and newly emerging infectious diseases. We argue that the current focus on spatial aberrations has limited the development of public health surveillance by excluding a more explicit geographical understanding and representation of place. A more place-focused public health surveillance could represent geography in ways that are useful to a broader audience, provide information on the social and physical contexts related to health, facilitate a better understanding of health inequalities, and can benefit from local knowledge. Geographers can make important contributions to public health practice by contributing to more meaningful definitions of place in the design and operation of publichealth surveillance systems.