City Of Edmonton Research Articles

Edmonton's Wayfinding Journey ( breakout presentation )

The session will comprise a presentation by the City of Edmonton on why they decided to pursue the development of a coordinated City approach to wayfinding systems. We will cover the development of objectives, the value case that needed to be made, pilot project evaluation and their perspectives on how wayfinding helps people perceive and use their city on foot. In 2012, the City of Edmonton embarked on a walking wayfinding project as one of the goals of our walkability strategy. Objectives included wanting to encourage people to walk in a northern city, to find ways to communicate the complex indoor Pedway network and to help reconnect neighbourhoods where driving dominates. The City of Edmonton engaged Applied Wayfinding to prepare strategies, a business case and pilot projects, and to design both an interim and permanent on-street signage system. We were fortunate to at the same time to design a system to update wayfinding within our Downtown Pedways that would coordinate with the on-street system and to begin to coordinate with our Parks and Transit systems. We are currently implementing the permanent system. The results of the pilot showed that people respond very similarly to information that helps them explore confidently on foot. This evidence of people’s willingness to walk if they can orientate themselves, understand the proximity by walking and be engaged in the character of the place, helped the City to successfully adopt a wayfinding program that is growing to be a significant aspect of our work in active transportation. The session aims to provide insight and interest for the audience on how a technique with limited widespread understanding like wayfinding can become a supported initiative. The Edmonton project also reveal the difficulties in finding measurable programs to increase walking in the short-term as well as the interest and questions about the role of mobile technology, accessible information and managing design-based projects in transportation.

Vibrant Pedestrian Retail in Edmonton: Challenges and Opportunities ( breakout presentation )

Background Varying forms and locations of retail environments offer different levels of accommodation for active transportation. Like many North American cities, the retail environment in Edmonton, Alberta experienced significant change throughout the last century. Before World War II, traditional retail forms in central areas and main streets were accessible on foot and by streetcar lines. The post-war suburban shift and rise of automobile-dependence challenged the success of these walkable and social landscapes. Municipal policies shifted to support the proliferation of suburbs and new auto-dependant forms of retail competition such as malls and big-box outlets. This undermined pedestrian retail in two respects: first, new retail forms were not accessible on foot; second, increased competition led to the decay of traditional walkable retail environments. Since the 1990s, the City of Edmonton has developed policies to revitalize traditional commercial areas, but these initiatives have seen limited success. Aim To identify challenges and opportunities in the implementation of policies that promote the revitalization of walkable traditional retail areas in Edmonton. Method Over 50 informants with professional knowledge of retail areas were interviewed in this case study. They included city planners, politicians, local organizations, business revitalization zones, retailers, developers, and lending agencies. Results Edmonton’s policies to revitalize walkable urban retail areas are well developed. However, they have been undermined by remnants of policies and practices that promote suburban retail forms. As such, transitioning the retail environment to reflect contemporary planning values that promote vibrant, accessible, and walkable places has been a slow and arduous process. Likewise, retailers and developers face established practices that make locating in central urban areas challenging. Transitions towards sustainable forms of development can be enhanced by intentional actions that disrupt deeply entrenched processes. For instance, the formation of functional work groups to tackle issues in city administration created incentives for retailers and developers to make central urban location choices. Conclusions Encouraging denser and more walkable retail forms requires municipalities to challenge entrenched processes and policies that undermine sustainable planning principles. To eliminate incentives to develop auto-dependant retail and successfully promote walkable retail areas, policies and implementation strategies must be effectively combined.

School zone safety diagnosis using automated conflicts analysis technique

School safety is a high priority for road safety agencies worldwide due to the growing concerns about student safety and emphasis on community livability. However, the lack of consistent data available at schools makes it challenging for engineers to understand the safety issues faced accurately. Traffic conflicts have been advocated in the literature as a surrogate safety measure due to the advantages it offers for road safety evaluations. This paper demonstrates the capability of automated traffic safety diagnosis at a school using computer vision techniques. The selected school is located in a residential area in the City of Edmonton, Alberta, and is on a main roadway in the neighbourhood. The age group of the school is from 5 to 16 years old (corresponding to Grade 1 to 9 respectively). Data are collected during the fall and winter terms. The severity and frequency of conflicts and traffic violations were analyzed to quantify the safety concerns. These concerns included driving violations, jaywalking violations as well as conflicts between pedestrians and vehicles as well as between vehicles and each other. Hourly and seasonal trends were observed and analyzed to assist in the selection of treatments and recommendations to improve the safety around schools. The results show that pedestrian safety has improved in winter due to lower vehicle speeds.

Bioconcentration of polycyclic musks in fathead minnows caged in a wastewater effluent plume

The synthetic polycyclic musks HHCB (Galaxolide®) and AHTN (Tonalide®) were monitored in fathead minnows (FHMs) caged for a month at various locations in the North Saskatchewan River (NSR), upstream and downstream of the Gold Bar wastewater treatment plant that serves the city of Edmonton, AB, Canada. In addition, the distribution of these musk compounds in the river was predicted using the fugacity-based Quantitative Water Air Sediment Interface (QWASI) model. In FHMs caged 0.15 km downstream of the wastewater outfall, mean concentrations of HHCB and AHTN were 7.4 and 0.4 μg g−1 wet weight, respectively. These are among the highest reported concentrations of these musk compounds in fish exposed to treated wastewater. The musk concentrations in FHMs were significantly lower further downstream of the outfall. High bioconcentration factors (BCFs) in FHMs that exceeded 104 higher than estimated concentrations in water indicated that there were low rates of biotransformation of the musks in the fish. In the FHMs caged at the site closest to the wastewater outfall, HHCB concentrations in FHMs were comparable to the body burdens that have been reported to moderate expression of vitellogenin in female rainbow trout, indicating that fish in the NSR downstream of the wastewater outfall may be at risk of anti-estrogenic effects. The QWASI model applied to six individual river sections of the NSR predicted that the largest fluxes of HHCB and AHTN would be for downstream transport in water, which explains why FHMs accumulated elevated concentrations of the musks at the furthest downstream site, 9.9 km from the wastewater discharge.

Lake-sediment record of PAH, mercury, and fly-ash particle deposition near coal-fired power plants in Central Alberta, Canada

We report a historical record of atmospheric deposition in dated sediment cores from Hasse Lake, ideally located near both currently and previously operational coal-fired power plants in Central Alberta, Canada. Accumulation rates of spheroidal carbonaceous particles (SCPs), an unambiguous marker of high-temperature fossil-fuel combustion, in the early part of the sediment record (pre-1955) compared well with historical emissions from one of North America's earliest coal-fired power plants (Rossdale) located ∼43 km to the east in the city of Edmonton. Accumulation rates in the latter part of the record (post-1955) suggested inputs from the Wabamun region's plants situated ∼17–25 km to the west. Increasing accumulation rates of SCPs, polycyclic aromatic hydrocarbons (PAHs) and Hg coincided with the previously documented period of peak pollution in the Wabamun region during the late 1960s to early 1970s, although Hg deposition trends were also similar to those found in western North American lakes not directly affected by point sources. A noticeable reduction in contaminant inputs during the 1970s is attributed in part to technological improvements and stricter emission controls. The over one hundred-year historical record of coal-fired power plant emissions documented in Hasse Lake sediments has provided insight into the impact that both environmental regulations and changes in electricity output have had over time. This information is crucial to assessing the current and future role of coal in the world's energy supply.

AFFORDABLE HOUSING POLICY IMPLEMENTATION MUNICIPALITIES: A CASE STUDY

The city of Edmonton, the fifth largest municipality in Canada, passed the Affordable Housing strategy in year 2015. The strategy formalizes the City’s role in the effort to bring affordable housing to needy residents and outlines the framework to engage the stakeholders for effective implementation. The strategy’s goals include increasing the supply of affordable housing in all areas of the City. This paper focuses on a critical analysis of this goal – especially the implementation phase of the policy. Combining evidence-based implementation has performed analysis, lessons learned from best practices across the globe and presented using the NATO model. Based on the critical analysis, this paper provides recommendations for an effective implementation of affordable housing policy, which can be adapted to other municipalities in Canada.

Concentrations, sources and human health risk of inhalation exposure to air toxics in Edmonton, Canada

With concern about levels of air pollutants in recent years in the Capital Region of Alberta, an investigation of ambient concentrations, sources and potential human health risk of hazardous air pollutants (HAPs) or air toxics was undertaken in the City of Edmonton over a 5-year period (2009–2013). Mean concentrations of individual HAPs in ambient air including volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs) and trace metals ranged from 0.04 to 1.73 μg/m3, 0.01–0.54 ng/m3, and 0.05–3.58 ng/m3, respectively. Concentrations of benzene, naphthalene, benzo(a)pyrene (BaP), arsenic, manganese and nickel were far below respective annual Alberta Ambient Air Quality Objectives. Carcinogenic and non-carcinogenic risk of air toxics were also compared with risk levels recommended by regulatory agencies. Positive matrix factorization identified six air toxics sources with traffic as the dominant contributor to total HAPs (4.33 μg/m3, 42%), followed by background/secondary organic aerosol (SOA) (1.92 μg/m3, 25%), fossil fuel combustion (0.92 μg/m3, 11%). On high particulate air pollution event days, local traffic was identified as the major contributor to total HAPs compared to background/SOA and fossil fuel combustion. Carcinogenic risk values of traffic, background/SOA and metals industry emissions were above the USEPA acceptable level (1 × 10−6), but below a tolerable risk (1 × 10−4) and Alberta benchmark (1 × 10−5). These findings offer useful preliminary information about current ambient air toxics levels, dominant sources and their potential risk to public health; and this information can support policy makers in the development of appropriate control strategies if required.

Traffic Conflict–Based Before–After Study with Use of Comparison Groups and the Empirical Bayes Method

Road safety evaluations mainly rely on the analysis of crash data that are challenged by well-recognized availability and quality issues. The statistical models used to predict the safety level of road sites—that is, safety performance functions—have recently been successfully developed with the use of traffic conflict observations instead of crashes. As such, it is possible to adopt and transfer the statistical techniques used in crash-based road safety analysis to conflict-based analysis. The use of statistically rigorous techniques in crash-based before-and-after (BA) studies is essential for evaluation of the effectiveness of road safety countermeasures. In particular, the use of Bayesian methods, such as the empirical Bayes (EB) technique, is vital to control for confounding factors that can operate simultaneously with the countermeasure and may affect road safety performance. The main objective of this paper was to estimate the treatment effectiveness of two traffic signal (visibility) improvement projects in the city of Edmonton, Alberta, Canada, with a conflict-based BA study using the comparison group and the EB methods. More than 300 h of video data with traffic conflict observations was automatically collected and analyzed by computer vision techniques for two treatment intersections and two control (untreated) intersections before and after the signal improvement projects. The results of the comparison group method showed a statistically significant 24% reduction in the average number of rear-end conflicts per hour, whereas the EB method showed a statistically significant 24.5% reduction in the average number of total conflicts per hour.

Operating Speed Models for Tangent Segments on Urban Roads

Information about operating speeds is essential to design better roads, model traffic emissions, and ensure design consistency while efficient and safe operations on roads are maintained. Therefore, understanding how different factors affect operating speeds and developing operating speed prediction models are critical research issues. Many studies have developed such models on rural roads and highways, but only a few studies have considered development of such models on urban roads and fewer still on tangential segments. This present study attempted to address these limitations by developing operating speed models with data from 249 tangential road segments in the city of Edmonton, Alberta, Canada. A generalized linear model was developed with panel data, and the primary aim was to explore the relationships between operating speeds on urban roads and features of the road environment. To study the impact of road elements on different road types, three models were created: one that combined arterial and collector locations, one for arterials only, and one for collector roads only. The results revealed that roads with sidewalks that were farther away from the road and with low object density or tree density were all associated with higher operating speeds. Locations with monolithic walks on both sides of the road had lower operating speeds. Furthermore, operating speeds decreased as access increased, while longer roads had higher operating speeds. One major takeaway was that the elements differed between road classes. The two variables, which stood out in that respect, were medians and bus stops.

The dilemma of scaling up local food initiatives: Is social infrastructure the essential ingredient?

The purpose of this paper is to reflect on and compare two responses to the challenge of scaling up local food initiatives. Comparative case studies of the Good Food Box in the City of Edmonton and the Rimbey farmers’ market are used to examine the different strategies used to scale up their impacts as a means of providing a meaningful alternative to the status quo. Our findings suggest that investments in social infrastructure are crucial for maintaining the values and integrity of local food initiatives and also to highlight the challenges of doing so while in competition with the mainstream food system. Our research identifies how social infrastructure investments for local food initiatives can support radical and strategic incremental changes by managing the risk associated with transformative local food activities and provides opportunities for a reflexive approach to scale by identifying the levers and catalysts for broader change to ensure that investments in food system infrastructure are not made merely for the sake of scaling-up. Social infrastructure is identified as critical for building support for, and attention to, opportunities to scale out and develop connections, networks and partnerships for change beyond food.

Long-term impact of road salt (NaCl) on soil and urban trees in Edmonton, Canada

The application of de-icing salts for winter road maintenance is recognized as a major contributor to the decline of urban trees. We conducted a long-term monitoring program across several locations in the City of Edmonton (Alberta, Canada) to evaluate the impact of roadway salt application on tree species widely planted in boulevards and right-of-ways: Ulmus americana, Fraxinus pennsylvanica, Pinus contorta, and Picea glauca. Soil and leaf samples were collected from a total of 16 sites over six years. There were four sites selected for each tree species: three mid- to high- traffic roadside sites that received regular winter maintenance and one non-serviced site (control). Sampling was performed three times per year from late spring to late summer. Airborne salinity was assessed in four locations at different distances from the road. In 50% of the roadside sites, soil electrical conductivity (EC) values exceeded 2dSm−1. Soil pH in all of the roadside sites was also significantly higher than in the control sites, with values ranging from 7.6 to 8.5. In all four species, trees growing in sites with high soil EC had increased leaf Na concentrations and reduced leaf chlorophyll concentrations. Among the airborne monitoring sites, Na deposition in high traffic locations was over four-fold higher than those measured in the control location. Furthermore, Na levels remained relatively high at 20–50m from the main road. Our data suggest that while soil salinity is among the main stressors affecting roadside trees in Edmonton, salt spray deposition may also have a significant impact on trees located close to high vehicle traffic areas and dense road networks. Our study highlights the importance of collecting data over several years and from multiple locations to account for the spatial and temporal heterogeneity of the urban environments in order to better evaluate the impact of road salt application on urban trees.

Gathering place: Urban indigeneity and the production of space in Edmonton, Canada

Abstract Most major Canadian cities have displaced existing indigenous settlements and gathering places. The city of Edmonton, Canada today includes what will soon be the nation’s largest urban Aboriginal population. Though urban space and planning reflect colonial relationships, it has launched progressive initiatives preceding and following the work of the national Truth and Reconciliation Commission (TRC). This article examines material and intangible traces of Aboriginal history and cultural presence in a theoretical context concerned with public spaces promoting transformative, dialogic, cross-cultural encounters. Case studies consider urban spaces as gathering places in terms of their relevance to indigenous practices of metissage. What is at stake for settler colonial cities in the recognition and inclusion of indigenous presence and historical relationships? Aboriginal cultures can and must play a critical role in the development of a mature civic identity rooted in a complex mutual history, with implications for urban social and ecological sustainability in the future.

Towards setting credible speed limits: Identifying factors that affect driver compliance on urban roads

Road geometry, vehicle characteristics, and weather conditions are all factors that impact a driver’s perception of a safe or credible speed and, consequently, the driver’s decision on whether or not to comply with the posted speed limit. In fact, the role a road’s environment plays in a driver’s perception of a credible speed limit is a topic that has attracted the interest of many researchers in recent years. Despite that, not many studies have considered using empirical data to investigate what features of the road environment influence a driver’s compliance choice. This paper aims to address this matter by exploring the relationships between features of the road surroundings (geometric, temporal factors, and weather conditions) and driver compliance with speed limits. The paper uses data from almost 600 different urban roads in the city of Edmonton, at which over 35 million vehicle spot speeds were collected. Compliance was represented using a categorical ordered response variable, and mixed-effects-logistic-regression models were fitted. Two different models were built, one for arterials and another for collector roads. In general, the findings show that the more restricted drivers become, particularly on arterials, the more likely drivers are to comply with speed limits; potential restrictions include on-street parking and the absence of lateral shoulders. Furthermore, higher traffic activity during peak hours, and presumably on shoulder weekdays, both increase the likelihood of compliance on arterials. Similarly, posted speed limits and traffic volume are both positively correlated with compliance on both arterial and collector roads. The findings of this research provide evidence of the existence of an empirical relationship between road features and compliance, highlighting the importance of setting credible speed limits on roads and the possibility of achieving higher compliance rates through modifications to the road environment.

Lesson learned from the application of intersection safety devices in Edmonton

The City of Edmonton began its intersection safety device (ISD) program in 2009 with the installation of 50 cameras throughout the city. The ISDs are approach-specific and combine automated enforcement of red-light running and speed violations during the red and green phases of the intersection control. The goal of this study is to evaluate the safety performance of ISDs within the city of Edmonton, Canada and to identify factors that can lead to successful selection of future ISD sites. A before-and-after Empirical Bayes (EB) method is used to account for regression-to-the-mean and other confounding factors. A safety performance function and yearly calibration factors are developed using data from a set of reference intersections within Edmonton. The before-and-after analysis is applied at the overall intersection level and for each approach of the ISD intersections. The results showed significant reductions that ranged from 12% to 25% for total collisions, and from 33% to 43% for angle collisions. No significant reduction was observed for severe collisions at the intersection level, however significant reductions were found at the approach level at locations with a relatively higher collision history. The impact of site selection criteria on collision reduction was also evaluated. Greater reductions were found at sites with a higher collision frequency. Additionally, the impact of intersection characteristics on collision reduction was investigated. Speed limits, presence of separated right turn lane and the number of lanes were found to impact ISD collision reduction.

Characterizing New Channels of Communication: A Case Study of Municipal 311 Requests in Edmonton, Canada

City governments around the world are developing and expanding how they connect to citizens. Technologies play an important role in making this connection, and one frequent way that cities connect with citizens is through 311-style request systems. 311 is a non-emergency municipal notification system that uses telephone, email, web forms, and increasingly, mobile applications to allow citizens to notify government of infrastructure issues and make requests for municipal services. In many ways, this process of citizen contribution mirrors the provision of volunteered geographic information, that is spatially-referenced user generated content. This research presents a case study of the city of Edmonton, Canada, an early adopter of multi-channel 311 service request systems, including telephone, email, web form, and mobile app 311 request channels. Three methods of analysis are used to characterize and compare these different channels over three years of request data; a comparison of relative request share for each channel, a spatial hot spot analysis, and regression models to compare channel usage with sociodemographic variables. The results of this study indicate a shift in channel usage from traditional to Internet-enabled, that this shift is mirrored in the hotspots of request activity, and that specific digital inequalities exist that reinforce this distinction between traditional and Internet-enabled reporting channels.

Contrasting "back home" and "here": how Northeast African migrant women perceive and experience health during pregnancy and postpartum in Canada.

BackgroundInternational migration and the number of migrant women who experience pregnancy and childbirth in receiving countries have significantly increased in the last two decades. Migrant women often have unmet social and economic needs during pregnancy, and are more likely to have problems unaddressed by health care systems. In this qualitative study, we explored migrant women’s perceptions and experiences of health during pregnancy and postpartum, while participating in a perinatal program offered through a community-based organization. Additionally, we examined sociocultural factors that might have shaped women’s health upon migration to the Canadian city of Edmonton, Alberta.MethodsA community-based participatory research approach was used to engage migrant women connected to a community-based perinatal program in Edmonton. A focused ethnography was conducted with four Northeast African communities (Eritrean, Ethiopian, Oromo and Somali), and involved 10 focus groups with women (n = 8, per group) and direct observations of weekly perinatal program activities. Data generation and analysis occurred concurrently, and all generated data were analyzed using qualitative content analysis to inductively derive codes and categories.ResultsWomen expressed their perceptions and experiences of health during pregnancy and postpartum by contrasting their countries of origin with Canada, respectively identified as “back home” and “here”. Differences in social support and the physical environment (both natural and built) between “back home” and “here” were commonly described as factors that shaped their opportunities to eat healthy, be physically active and emotionally well before and after having a baby “here”. Overall, women described that in Canada they lacked the social and environmental factors perceived as key enablers of healthy pregnancies and postpartum.ConclusionA complex network of factors seem to influence Northeast African women’s health during pregnancy and postpartum upon migration to Canada. It is of the utmost importance to provide these women with the immediate sociocultural and environmental factors they need to successfully thrive during pregnancy and postpartum, especially while establishing social and support networks “here”.

Operating a mobile photo radar enforcement program: A framework for site selection, resource allocation, scheduling, and evaluation

This paper introduces a systematic, data-driven framework by which to operate a mobile photo radar enforcement (MPRE) program, consisting broadly of site choice, enforcement resource allocation and scheduling, and evaluation. The overall goal is provide a framework for operating an MPRE program that is well-defined and replicable, in order to improve efficiency in deploying finite enforcement resources and efficacy in improving traffic safety. To illustrate the process, the proposed program was applied to simulate a deployment plan for one month using data from the City of Edmonton. The results of program application were assessed against the results of the existing MPRE program in place in May 2014, using several candidate short-term evaluation measures. Based on the results, it is expected that with implementation of the proposed program, the City of Edmonton’s MPRE program may observe moderate to high improvements in travel distance efficiency and coverage of sites with safety issues. The promising test results do further indicate the need for a full-scale, real-life deployment of the proposed program. This proposed MPRE program design framework can provide planners, engineers, and law enforcement professionals with a systematic, analytic, and data-driven process by which to operate a MPRE program. Despite that the design framework was built in response to the needs of the City of Edmonton’s current MPRE program, its development was generalized for adaptation and adoption within any jurisdiction looking to begin a new program, or make improvements to an existing one, in their pursuit of greater traffic safety.

Relationship between road safety and mobile photo enforcement performance indicators: A case study of the city of Edmonton

ABSTRACTMobile photo enforcement (MPE) programs are commonly implemented to regulate speed and improve road safety. However, most previous research focuses mainly on validating the safety effects of MPE, with very minimal discussion on the enforcement performance indicators (EPIs). Therefore, the goal of this study is to provide a better understanding of the relationship between the three selected EPIs (number of enforced sites, average check length, and number of issued tickets) and the program's safety outcomes. In total, 8 years (2005–2012) of monthly citywide data were collected and used in a generalized linear Poisson model. The results show that as the number of enforced sites and issued tickets increased, the number of speed-related collisions decreased. Also, as the average check length decreased, a greater reduction of speed-related collisions was observed. These results indicate that collision reductions were associated with a MPE program that promoted: higher spatial coverage (i.e., more enforceable locations), more frequent checks (i.e., shorter average check length), and more issued tickets. The marginal effects of enforcing 100 sites and issuing 10,000 tickets per month were calculated to be 47 and 140 fewer speed-related collisions, respectively.

Dust is the dominant source of “heavy metals” to peat moss (Sphagnum fuscum) in the bogs of the Athabasca Bituminous Sands region of northern Alberta

Sphagnum fuscum was collected from twenty-five ombrotrophic (rain-fed) peat bogs surrounding open pit mines and upgrading facilities of Athabasca Bituminous Sands (ABS) in northern Alberta (AB) in order to assess the extent of atmospheric contamination by trace elements. As a control, this moss species was also collected at a bog near Utikuma (UTK) in an undeveloped part of AB and 264km SW of the ABS region. For comparison, this moss was also collected in central AB, in the vicinity of the City of Edmonton which is approximately 500km to the south of the ABS region, from the Wagner Wetland which is 22km W of the City, from Seba Beach (ca. 90km W) and from Elk Island National Park (ca. 45km E). All of the moss samples were digested and trace elements concentrations determined using ICP-SMS at a commercial laboratory, with selected samples also analyzed using instrumental neutron activation analysis at the University of Alberta.The mosses from the ABS region yielded lower concentrations of Ag, As, Bi, Cd, Cu, Pb, Sb, Tl, and Zn compared to the moss from the Edmonton area. Concentrations of Ni and Mo in the mosses were comparable in these two regions, but V was more abundant in the ABS samples. Compared with the surface vegetation of eight peat cores collected in recent years from British Columbia, Ontario, Quebec and New Brunswick, the mean concentrations of Ag, As, Bi, Cd, Cu, Mo, Ni, Pb, Sb, Tl and Zn in the mosses from the ABS region are generally much lower. In fact, the concentrations of these trace elements in the samples from the ABS region are comparable to the corresponding values in forest moss from remote regions of central and northern Norway.Lithophile element concentrations (Ba, Be, Ga, Ge, Li, Sc, Th, Ti, Zr) explain most of the variation in trace metal concentrations in the moss samples. The mean concentrations of Th and Zr are greatest in the moss samples from the ABS region, reflecting dust inputs to the bogs from open pit mines, aggregate quarries, and gravel roads. Linear regressions of V, Ni, and Mo (elements enriched in bitumen) versus Sc (a conservative, lithophile element) show excellent correlations in the mosses from the ABS region, but this is true also of Ag, Pb, Sb and Tl: thus, most of the variation in the trace metal concentrations can be explained simply by the abundance of dust particles on the plants of this region. Unlike the moss samples from the ABS region and from UTK where Pb/Sc ratios resemble those of crustal rocks, the moss samples from the other regions studied yielded much greater Pb/Sc ratios implying significant anthropogenic Pb contributions at these other sites.

Exploring the association between speed and safety: A path analysis approach

Road safety is influenced by many factors; these factors include characteristics of the road, climate, traffic and, most importantly, vehicle speeds. Previous research shows that increases in speed are typically associated with an increased collision risk. Moreover, previous studies have also found relationships between road and traffic characteristics and collisions. In addition, these features have also been found to affect speeds. This paper aims to model all the aforementioned relationships simultaneously using a Structural Equation Modelling approach. More specifically, the paper attempts to model the relationship between average speed and collision frequency, while taking into account the effects of factors that confound the relationship. Moreover, the analysis attempts to assess the mediated effects that some variables have on collisions through their effects on speed. The data used in this study originated from 353 two-lane urban roads in the city of Edmonton, Canada. The average speeds were obtained from 35 million speed survey observations collected over a five-year period. The speed data are linked to the crash frequency at each location during the same time frame, along with the other factors (road, traffic and climate). The results show that, among others, average speed, volume, segment length, medians and horizontal curves all have statistically significant effects on collisions. On the other hand, shoulders, speed limits and vehicle-lengths are some variables that significantly influence speeds. The results also show that the effects of some variables on safety are indeed mediated through speeds (both partial and full mediation is observed). These findings provide valuable insight that may assist decision makers in choosing and developing alternative speed management strategies, which, in turn, could help improve safety.