Reducing the Footprint Behind Your Footprints Around Town

By Beatrix Teng, Priti Das, Krithika Satish, Himani Nijhawan

Problem Overview

The transportation industry is one of the biggest contributors to global warming. 27% of 2020 greenhouse gas emissions were from the transportation sector, making it the largest source of greenhouse gas emissions in the United States (1). Unfortunately, individuals still do not have access to technology in which they can easily monitor their carbon footprint from their transportation. Consequently, it is harder to compare and select more sustainable modes of transportation that work for the individual’s needs.


With our app, Sustainable Slay, users can monitor and decrease their carbon footprint. Their transportation carbon footprint can be tracked automatically using location data and city public transport data. The app also provides navigation, recommending a best route for users based on carbon emissions, time, and price. This will allow people to analyze their own impact on the environment, and then feel empowered to reduce it as they weigh the environmental, monetary, and time costs of their travel options.

Paper Prototype, Testing Process, and Results

We first tested our idea using a paper prototype in which we had multiple hand-sized slips of paper that were mockups of different pages of the app.

Figure 1: All possible user flows using paper prototype

The above figure shows all the possible user flows using the paper prototype. The home page of the app is on the left, and then as the test user presses different parts of the paper, one can follow the green arrows and discover a new page of the prototype.

We tested this prototype on multiple people and identified six problematic issues with our design. The most salient issue was the fact that test participants did not know you could select different modes of transportation for the navigation feature. The page is shown in the figure below.

Figure 2: Most problematic, unclear page in our paper prototype test

This was quite a severe problem because navigation is one of the main features of our app. To fix this issue, we added a clear button for every transportation option so it is obvious the user can select that option for navigation. This is shown in the figure below.

Figure 3: Fixed digital mockup page of first issue

The second most interesting issue was that our total emissions graph did not clearly indicate that the emissions were the total emissions of that day. This is shown in the figure below.

Figure 4: Second most problematic, unclear page in our paper prototype test

This was also quite a severe problem because our participants could not easily tell if the emissions graph showed the total emissions over the course of the day, or the emissions for each individual mode of transportation. To fix this issue, we changed the y-axis title on the emissions graph and made it say “Total Emissions.” This is important because we want to market our app to be as easy to use as possible.

Figure 5: Fixed digital mockup page of second issue

Digital Mockup

First Task: Find your carbon footprint for today and compare that with your friends.

Second task: Use the app to find options to navigate to Kane Hall from your current location, and then navigate there.

We learned from user testing that there was some confusion regarding our page with transportation options. One change that we made from our paper prototype was adding a confirmation page after selecting a transportation method. This confirmation page reiterated the method of transportation chosen, as well as the environmental impact of the method. The page is highlighted in a color according to how carbon efficient it is. If the user would not like to continue with this method, there is a back button, in case they re-evaluated their choice and want to pick another one.

Another change that we added was on the page that lists all of the transportation methods to the given destination, including the time it takes, kilotons of carbon emitted and price.This page is formatted as a table and it was unclear that the users could hover over/select a method of transport. Therefore, we added to the top of the page a header that says, “Select Transportation”.

We also modified the compare with friends page, so that it was formatted more like a leaderboard. Through our testing, we received feedback that this was unclear. The friend with the lowest carbon emissions is at the top of the page in larger font and with a star. The friends following them are listed in order from least to most carbon efficient. There is also a drop down menu at the top of the page that allows you to compare over today, a week, a month and a year.

Link to final digital mockup:


In our initial user research, we found that while individuals wish to reduce their carbon emissions, they prioritize time and efficiency because they are unaware of greener alternatives. Therefore, we visualized a solution that would help users effortlessly collect data on their personal carbon emissions, and offer them alternative energy-efficient routes for their daily commutes. Our app further encourages the reduction of carbon emission by enabling users to compare their emissions with friends and use the in-app navigation option to easily choose a greener transportation option.



University of Washington Computer Science, Intro to Human Computer Interaction

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CSE 440 Staff

University of Washington Computer Science, Intro to Human Computer Interaction