Shaping Conversations about Transit with Interactive Isochrone Mapping
Engaging stakeholders in dialogue about proposed transportation projects is often a challenge. Public deliberations about bus-only lanes, for example, are often dominated by stakeholders tied to a narrow corridor and their concerns about localized disruptions; the wider population of potential corridor users may not realize they stand to gain, let alone advocate for a project when benefits seem speculative. Furthermore, if stakeholders suggest changes, the time and technical expertise needed to analyze their feedback using traditional transport models may lead them to disengage or regard the process with suspicion. Over the past years, Conveyal has supported numerous conversations about public transport with interactive mapping tools, and we’ve learned some lessons about meaningfully engaging stakeholders in these conversations.
In this post, we describe how researchers have tested interactive mapping tools in stakeholder engagement workshops, catalog examples of similar online tools, and share interactive mapping tools we just released for Los Angeles and Toronto. But first, an introduction to the cartographic representation that all of these tools have in common — isochrones.
What are Isochrones?
You’ve likely seen isochrones used on popular websites. Real-estate site Trulia is one example. LinkedIn recently launched “Your Commute,” which asks job-seekers where they will begin their commutes, which mode they prefer, and how long they are willing to travel. If, for example, you set a limit of 45 minutes of travel by public transport, opportunities located beyond that limit are hidden. Enclosing the area accessible within the selected time limit is a boundary of equal time, or isochrone.
Isochrones show how transport networks provide accessibility to a range of potential destinations. They can shift peoples’ focus from the everyday grind of their current commutes, with fixed origins and destinations, to new possibilities for living, working, or traveling. While transport modelers have long produced static isochrone maps, advances in web-based maps now allow broader audiences to interact with isochrones.
In a 2018 issue of the Journal of Public Transportation, Jarrett Walker argues that given such advances, isochrones — and the freedom to access opportunities they represent — should be more central in deliberations about public transport. In an article published a month later, Cara Giaimo offers this analysis of “why isochrone maps are enjoying a renaissance”:
The increasing availability of geographical and transit-related data has led to an explosion in isochrone experiments… When you can actually see the time it takes to get somewhere or do something, inequalities and opportunity gaps become more apparent, and sometimes more visceral.
Interactive isochrone maps can make the network effects of transit “more apparent” and “more visceral.” This power makes them effective tools for agencies seeking to shape conversations about public transport projects.
Testing Isochrone Maps in Stakeholder Engagement Workshops
As discussed above, stakeholder engagement efforts for public transport projects often face numerous challenges, including:
- Salience of localized disruptive impacts, which may attract more attention than marginal or nebulous travel-time savings
- Under-involvement of stakeholders who live outside the boundaries of a project and do not realize they stand to benefit from it
- Long turnaround time to analyze suggestions, discouraging meaningful feedback
In addressing these challenges, we’ve found interactive maps, showing accessibility indicators and isochrones for both a baseline network and a proposed future scenario, to be helpful. Maps that can be zoomed and panned help users orient themselves using familiar locations, making results more personalized and relevant. Even if a project will not improve a user’s commute to one specific destination, superimposed isochrones show how access to other potential destinations would be improved. And because these maps show only first-order changes in travel time, without trying to predict follow-on changes in demand or crowding, they do not require lengthy assignment calculations. Results are available in seconds.
Researchers have tested accessibility- and isochrone-based planning in a wide variety of stakeholder engagement workshops. In Europe, a COST action assessed the usability and usefulness of dozens accessibility-based tools. The MIT Mobility Futures Collaborative has been testing CoAXs, a tool backed by Conveyal Analysis, in other international workshops. While such research shows promise, as summarized in this volume of Transportation Research Part A, many of these experimental tools are designed to answer specific research questions and are not especially reliable, intuitive, or usable for general audiences.
Other Examples of Interactive Isochrone Maps
Other online tools, for both status quo and future transport networks, are increasingly intuitive and readily available. Tools like Mapbox Isochrones, Mobility Explorer, and the iGeolise Travel Time Platform can unlock insights into how well existing networks serve different places in a region. Azavea’s GoPhillyGo (which uses OpenTripPlanner) and Sidewalk Labs’ Totx (which uses R5) are other good examples.
Going beyond today’s networks, a number of custom tools allow users to compare current service and future scenarios. The interactive “time mapping” feature of Transport for London’s WebCAT allows users to compare networks based on forecast years, step-free access requirements, etc. Other examples include Remix’s Jane (showing circular buffers around transit stops) and dashboards used in Moscow and Richmond.
Many of these comparative, scenario-planning tools require substantial software development effort to code networks and customize user interfaces. And with some, users must wait for lengthy computation, which may limit the responsiveness of tools or the size and complexity of the networks considered.
Interactive Accessibility Sites Published from Conveyal Analysis
In light of the limitations above, Conveyal has continued to develop and test our own mapping tools, supporting stakeholder engagement in Europe and North America. In the Netherlands, such published results will be the basis for ongoing performance monitoring of changes to the national rail network.
In another example, as part of Focus40 Long Range Plan for Boston’s MBTA, we customized a mapping tool for a large touchscreen used at an open house conducted by the Massachusetts Department of Transportation. Many attendees enthusiastically engaged with map, testing their commutes and access to jobs under different scenarios like the Green Line Extension, contributing to the overall success and “cool factor” of the event.
Recent optimizations in the R5 routing engine have further reduced the time and computational power needed to publish these sites, and we decided to create a few more for new contexts. Multiple North American agencies are considering upgrading legacy commuter rail networks to electrified, frequent, all-day service, and these projects, which have potentially transformative yet difficult to communicate benefits, seemed like ideal test cases.
Metrolink, the commuter rail operator for greater Los Angeles, released a regional rail vision called Southern California Optimized Rail Expansion (SCORE), which calls for increased frequencies across the network, operating every-30-minute service on most lines. To model these upgrades, we started with a baseline network of a large OpenStreetMap extract and 71 GTFS feeds (including Metrolink, Metro Bus, Metro Rail, Amtrak, and a plethora of municipal transit operators). For simplicity, we used the scenario editing functionality of Conveyal Analysis to select the fastest inbound and outbound trips for each of Metrolink’s lines and replicate them every 30 minutes. This simplification ignores SCORE’s plans for coordination between lines, express overlays, and through-running of trains enabled by LinkUS, but these would be straightforward refinements to add. We also extended the Purple Line Extension to Westwood and the Blue and Expo Lines to Union Station (representing the Regional Connector), and we added light rail currently under construction in the Crenshaw/LAX corridor.
With this 2028 Rail Expansion scenario in place, we published a proof-of-concept interactive accessibility site allowing users to compare accessibility and travel times by public transport across Southern California. We calculated the total travel time (walking, waiting, and in-vehicle time) for trips starting at every minute between 7 AM and 9 AM, then reported the median travel time in the published results. If passengers adjust the starting time of their trips to align with transit schedules, they will likely experience shorter travel times than the median; if they are unlucky and just miss a train or bus, they will experience longer travel times.
Consider a hypothetical traveler, Bob, who travels from Buena Park to UC Irvine. With the Metrolink Orange County Line running every 30 minutes, as in the SCORE vision, the median total time to walk to the Buena Park Station, ride to Tustin, wait for OCTA Route 473, ride that bus, and walk to the final destination is about an hour and a half. With today’s less frequent Orange County Line trains, Bob’s trip takes 113 minutes — 20% longer. Adjusting his departure time so he doesn’t have long waits at the station or transfer point may reduce his total travel time; but having to adjust his morning routine to meet transit schedules may impose inconvenient constraints. As the Jarrett Walker slogan says, “frequency is freedom.”
In addition to showing the difference in travel times, the graphic above shows the difference in accessibility to jobs. Without the SCORE upgrades, Bob would have access to 36% fewer jobs. Looking at these isochrones, Bob might be surprised that within the same travel time limit, the upgraded network also allows him to reach Beverly Hills and UCLA:
In the baseline network, transit from Buena Park to UCLA would take well over two hours, with the fastest trip requiring transfers from Metrolink to the Red Line, then the Expo Line, then the Culver City 6 bus. With SCORE and the Purple Line Extension, the trip is much shorter and requires only one transfer, as shown above. Even if Bob himself were a committed UC Irvine Anteater, uninterested in working at UCLA, the isochrones might help convince him of the wider benefits of a project like SCORE and make him a more enthusiastic participant in conversations about it. Pressing the play button animates these isochrones, communicating these wider benefits of expanded access dynamically.
We prepared a similar proof-of-concept interactive site for Toronto, where Metrolinx upgrades promise to transform the existing commuter rail system into a frequent, RER-like network. Even with frequency upgrades for only the Union-Pearson Express and Lakefront lines included, the increased access to the region’s workforce is widespread.
In a modern browser, these interactive sites load quickly regardless of how many users are accessing the site, because all results are pre-calculated. This speed can help encourage iterative exploration and dialogue.
Next Steps
Extensions of these sites could compare different combinations of modes (e.g. walking+transit vs. biking+transit vs. scooter+transit) or other scenarios formatted in Conveyal Analysis. Conveyal’s software is modular and open-source, so it is straightforward to customize similar sites for specific projects or engagement campaigns.
We’d love your feedback on this post. Do our observations align with your experiences engaging stakeholders and shaping conversations with interactive tools? Are there important interactive isochrone mapping tools we missed? As always, feel free to get in touch.
This post is the second in our series on interactive accessibility sites. The first covers Conveyal’s award-winning(!) site for Tokyo 2020. The third outlines some of the technical innovations enabling these sites.
