App of the Month: Map of Accident-Prone Road Segments

August 1, 2019 Mingsze Ho

As a GIS analyst, I create a lot of maps and applications that cater to a wide range of users. Many people think the biggest challenge of my work is thinking of a topic to work with. From experience, the hardest part is not coming up with the topic but the data. First, you need to find and retrieve the data, clean it (data can be messy sometimes, and it takes an analyst to translate the data into something meaningful) and organize it. This process is exactly what the Regional County Municipality of Brome-Missisquoi follows to keep their data well maintained for building applications like August’s App of the Month, Cartographie des tronçons routiers accidentogènes, which maps the location of accidents for the public to see.

The Regional County Municipality of Brome-Missisquoi is predominantly made up of rural areas in the eastern region of Québec, just south of Montréal. It encompasses 21 local municipalities with Cowansville being the largest city. Only four municipalities began with GIS integrated with their assessment team, and they worked over the years to integrate 17 other municipalities in their GIS system. Since then, they have built various up-to-date datasets accessible to their staff and the public. With a strong integrated GIS foundation in place, they built Cartographie des tronçons routiers accidentogènes to map the location of accidents within the municipality.

In 2016, the municipality embarked on a campaign to promote active lifestyles, focusing on active transportation and mobility. To do that, they had to ensure the number one concern of active transportation was met, and that was safety. They compiled 10 years’ worth of road accidents that have happened in the municipality and created an application. Data on 12,000 accidents were collected and recorded on a spreadsheet. They geocoded these points to show the distribution of accidents and identified roads and intersections that might need infrastructure changes to accommodate the active lifestyle the municipality was trying to promote.

Using Web AppBuilder for ArcGIS, the municipality created an interactive visual of accident information that allows for filtering options such as the number of fatalities, year in which the accident happened, the time of the day as well as the day of the week the accident happened. All filters are set to identify causations and isolate environmental variables that might have contributed to the car accident. For example, the function of the filter can be used by an urban planner trying to decide whether a road is prone to accidents during rush hour near a bus shelter.

Filter widgets allow you to see what environmental and temporal setting may cause accidents.

Aside from the simple filter widget, a Query widget can also be used to dive deeper into understanding the variables that might have caused different types of accidents. Users can pick a variable, in this case, the type of accident, and further filter down to predefined elements for a more specialized query.

From a cartographic perspective, I really like how the municipality symbolized the different types of queries.

The Query widget allows users to identify what variables contributed to certain types of accidents and where those accidents occurred.

This application is unique because it uses multiple methods of displaying data on a map, as shown above. At the initial extent of the map, the dots of all 12,000 accidents are displayed in a cluster using the clustering feature option. When this function is enabled, as you zoom in to the map, the point would get smaller and declutter. However, when you zoom out, areas of highly populated accidents would be represented by a large dot. And a friendly reminder, clusters do contain popups and you have the option of customizing them as shown in this app.

The app uses clustering with customized popups to present accident information.

Last but not least, the app includes custom widgets. Making custom widgets requires coding, so I recommend you search this library of custom widgets other users have created before making your own, to save time. In this application, there were two custom widgets added and they both help users to visualize statistics on car accidents that happened in a particular time frame. One widget allows you to see car accidents by day of the week, and the other displays accidents by time of day. Custom widgets allow you to design the experience and interactions you want your users to have with your data. To get started, I recommend reading this introductory blog post on creating custom widgets.

Web AppBuilder includes numerous out-of-the-box widgets that can allow users of your app to interact further with your data.

Cartographie des tronçons routiers accidentogènes is an effective application because it serves data and GIS capabilities to multiple audience groups and does it in a way that is user friendly. It makes good use of both out-of-the-box and custom widgets to enhance the user experience and increase their engagement with the data. Building this type of application requires good data and demonstrates the strong commitment and discipline that the Regional County Municipality of Brome-Missisquoi has in maintaining the quality of their data.

Have you built apps incorporating the various widgets in Web AppBuilder or developed your own custom widgets? Share your experience below.

About the Author

Mingsze Ho

Mingsze Ho is a GIS Analyst for Esri Canada. Fascinated with displaying data in a spatial way, she focuses on generating story maps and other applications using Esri technology. She discovered her passion for maps when she started colouring and drawing maps in elementary school, and she was determined to become a cartographer. Mingsze loves how a map can illustrate the ways that certain features or phenomena affect human lives. While obtaining a bachelor’s degree in Environmental Studies, she realized the world had moved on to digital maps. She was heartbroken initially, until she discovered the power of GIS and how it can be used to leverage both art and data to create beautiful, interactive maps. In her free time, Mingsze continues to draw maps. She just really likes maps.

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