Public Transit Equity

Imagine living in downtown Chicago, where it is easy to catch a bus or hop on the subway to get to work, visit friends, or run errands. If the transit system is well-connected, and stops are just a short walk from your home, this could make it convenient for you to rely on public transportation. Now, if someone lives in a small rural town where public transit might be limited to a few bus routes that only run a couple of times a day. The nearest bus stop could be several miles away, making it inconvenient to rely on public transportation. At the same time, some individuals may find it convenient to obtain services near their work or shopping locations, indicating that daily activity spaces other than residential locations can be more representative of origin in measuring public transit calculations. This highlights the importance of origin (location) in accessibility decision making.

Consider the example below:

• Apartment A: You are considering living in this apartment and the nearest bus stop is really close - only a 5-minute walk, and the bus comes often- every 10 minutes. However, the bus ride to downtown takes 20 minutes. Remember, walking to transit stops is often the most time-consuming part of a person's journey. Here, we can say that the difficulty involved in getting to your destination is low since the stop is closer, and the bus is frequent.
• Apartment B: You are considering living in this apartment and the nearest train station is close, only a 5-minute walk, but the train comes only every 30 minutes, and the ride downtown takes 25 minutes. The short walk is convenient, but the infrequent service increases the effort required as you may need to plan your trips carefully to avoid long waits, potentially limiting your flexibility and convenience.
• Apartment C: You are considering living in this apartment and the nearest subway station is a bit far - 15-minute walk, but the subway comes every 5 minutes, and the ride downtown takes only 10 minutes. The effort is higher due to the longer walk, but the subway is faster once you are on it.

In other words, opportunities that are closer and easier to reach are typically given more weight than those that are farther away or more challenging to access when determining the overall level of accessibility. Here, you are taking into account not just the distance to opportunities but also how convenient it is to reach them. The step below provides an example of how to quantify how easy it is for you to access public transit from your home:

• Identify transit stops: First, list all the public transit stops (e.g., bus stops, train stations) within a certain radius of your home. For example, there might be five bus stops and two train stations nearby.

• Determine proximity: Next, measure the distance from your home to each of these transit stops. Suppose Bus Stop A is 0.5 miles away, Bus Stop B is 1 mile away, Train Station A is 2 miles away, and so on.

• Assess Ease of Access: Consider how easy it is to reach each transit stop. Bus Stop A, despite being closer, might be harder to reach due to a lack of sidewalks or heavy traffic, making it less convenient. On the other hand, Train Station A might be 2 miles away but easily accessible by a direct and frequent bus route.

• Weight the transit stops: Assign weights to each transit stop based on their proximity and ease of access. Closer and more convenient stops will have higher weights. For example:

  1. Bus Stop A: Weight = 0.6 (because it’s close but difficult to walk to)
  2. Bus Stop B: Weight = 0.8 (a bit farther but easier to reach)
  3. Train Station A: Weight = 0.7 (farther away but very accessible by bus)

• Calculate overall transit accessibility: Add up the weighted scores of all the transit stops to get an overall measure of how accessible public transit is from your home. For instance:

  1. Bus Stop A: 0.6
  2. Bus Stop B: 0.8
  3. Train Station A: 0.7
  4. And so on...If you sum up these weighted values, you will get a total score that reflects how accessible public transit is for you. Higher scores indicate better accessibility, meaning that you have more convenient and nearby options for using public transit.

Every time we try to figure out how easy it is to get to different places; we have to think about the things that attract people to certain locations and the things that make those locations available for use. Keep in mind that, how they feel about traveling to a specific place and whether they find it appealing and their assessment of its attractiveness may differ from person to person because of individual preferences and varying resources commonly known as Person-level heterogeneity. For example, people with more money tend to have access to a wider variety of things to do and buy. Also, people who have a car can usually go to more places compared to those who do not have a car or cannot drive. However, in most transit equity measurements, the quality descriptions of what makes a place attractive are often ignored probably because it is hard to get all the data needed.

If your intention is to run errands, go shopping, or dine out etc., does public transit facilitate this type of travel? Envision residing in a neighborhood with superb public transit options. However, despite your neighborhood's excellent connectivity for commuting, it lacks local amenities or destinations that meet your needs the most (e.g. work). In this scenario, the neighborhood is highly accessible for commuting but less so for your daily needs.

Travel times are generally a much better measure of the effort or cost involved in making a trip since it means that accessibility for any activity type varies by travel mode. In addition, travel times can change depending on the time of day due to traffic (e.g. morning rush hour), how often public transportation runs(so if one leg is missed, how recoverable will entire the journey be), the speed of the journey (including wait times). A small variation in departure time, such as leaving at precisely 11:00am versus 11:03am, could significantly impact travel duration and the ability to access public transportation, depending on the timing of a person's departure in relation to the arrival of a public transport vehicle, as well as the level of coordination with service schedules for transfers.

Other factors discussed such as the appeal or availability are also determined largely by time. The appeal or availability of a place may change throughout the day because of things like when stores are open or how busy they are (for example, a popular restaurant might be fully booked and not able to take walk-in customers). However, when it comes to walk-based accessibility, distance works pretty well as a measure because the farther you have to walk, the more effort it takes to get there.

We can use certain signs to check if the system treats everyone fairly instead of just looking at distance or time. These signs help us see if some groups, like people with low income, different races, disabilities, or living in certain areas, have a harder time using public transportation. This way, we can work to make things fairer for everyone. Some key things to consider:

• Do low-income areas or disabled riders have the same access to bus stops and transit stations as wealthier areas?
• Can everyone afford the transit fares? Are there programs in place to assist low-income riders?
• Do marginalized communities have longer commutes to reach essential services such as jobs, healthcare facilities, education, and other essential services?
• Do existing plans highlight specific areas where interventions may be needed?
• Do existing solutions help in tracking improvements over time and evaluating the impact of policies and investments?

• This is the simplest way to measure distance. Imagine a direct line from your house to your friend's house on a map.
• This line does not consider any buildings, roads, rivers, or obstacles – it is the absolute shortest path between two points, as if you are flying like a bird.
• It is simple but not always practical. You cannot walk/drive through buildings or private property, so you may not actually be able to take direct path as it seems to portray.
• When it is useful: Quick Estimates- It provides a basic idea of how close two places are. Initial Planning- It is most useful when details about roads or paths are not available

• This measures the actual distance you would travel along streets, sidewalks, or transit routes.
• It is like the route you would get from a GPS when driving or walking somewhere and it is more accurate for daily life, but you might have to walk down your street, turn a corner, and cross at a crosswalk, which could make an actual distance become one mile instead of half a mile.
• When it is useful: Travel Planning - This is most useful if you want to know how far you will actually travel, for delivery route or mail services planning.

• This measure is similar to the distance along roads or paths measure except that instead of considering distance along streets, sidewalks, or transit routes the focus is now on the actual time ( in minutes) it takes to travel that distance.
• Even if two places are close, heavy traffic or limited bus schedules might mean it takes longer to get there. So, it accounts for factors like speed limits, traffic, stoplights, and public transit schedules.
• When it is useful: Emergency Services – For instance ambulances and fire trucks may need to know how long it will take to reach someone in an emergency situation. Commuting – It helps to determine how easily people can access essential services like hospitals or grocery stores.

Acknowledging individual differences can complicate accessibility calculations and may require additional data, computational, and technical support. A number of transit equity measures simplify this complexity by using container-based measures which assess accessibility by grouping all the opportunities within predefined geographic areas commonly referred to as "containers" - neighborhoods, census tracts, or block groups. These measures assume that everyone within the container shares similar characteristics and that the area's attributes can represent the experiences of its residents, which makes it easier to analyze and compare.

You can pull a number of data from the American Community Survey (ACS for different areas or employ a combination of techniques) for container measures. Potential examples include:

1. Count of Bus Stops Within a Neighborhood

   • The neighborhood acts as the "container."
   • By aggregating the number of bus stops within this container, we are assuming that the accessibility to bus services is uniformly available to all residents in the area.
   • This count can be added as a new column or field in the dataset representing that area.
   • This measure simplifies individual differences by treating the availability of bus stops as a characteristic of the entire area.

2. Block Groups Within a Half Mile Buffer of a Transit Stop

   • Each block group serves as a container.
   • By determining which block groups fall within the half-mile buffer, we are assigning an accessibility attribute to the entire block group.
   • These block groups are marked or categorized based on whether they meet this proximity criterion.
   • This approach assumes that everyone within the selected block groups has similar access to the transit stop.

3. Proportion of Commuters That Use Public Transit (via ACS)

   • The census tract is the container.
   • By linking ACS data to the census tract, we are attributing the commuting behavior to the entire area.
   • This proportion is added as a field in the dataset representing that census tract.
   • This measure assumes uniformity in public transit usage within the tract.

4. Travel Diary Summary by Area

   • The area (e.g., neighborhood) acts as the container.
   • Individual travel behaviors are aggregated to provide average or typical travel patterns for the area.
   • This approach assumes that the summarized data represents the experiences of all residents within the container.

5. Census Tract Estimate of Percent of Low-Income Residents (via ACS) Within Half a Mile of a Bus Stop

   • The census tract is the container.
   • Combines ACS data on low-income residents at the census tract level with spatial data on bus stop locations.
   • This measure assigns an accessibility attribute (proximity to bus stops) to the tract based on the aggregated data of its residents.
   • It assumes that the accessibility level is uniform for low-income residents within the tract.

6. Census Tract Estimate of Percent of Low-Income Residents (via ACS) Within a 30-Minute Public Transit Distance of any Grocery Store

   • The census tract serves as the container.
   • Merging ACS data on low-income residents with transit network data to calculate travel times to grocery stores.
   • The measure aggregates individual accessibility into a tract-level statistic.
   • It attributes the calculated accessibility level to all low-income residents within the tract.

Limitations of Container-Based Measures:

• Overgeneralization: Container based measure assumes everyone in the area is the same, ignoring individual differences.
• Border Issues: It does not account for people who might possibly cross boundaries to access opportunities in nearby areas.
• No Travel Difficulty Consideration: Moreover, it does not consider how hard or easy it is to reach these opportunities.

Think of this measure as counting all the places you can get to within a certain time or distance(cutoff) towards or away from an origin. For example, how many grocery stores can you reach within a 15-minute walk? Instead of just looking at the distance or time it takes to get somewhere, this measure focuses on how many opportunities are available within your travel limits. It includes all opportunities within the cutoff and excludes those beyond it.

A cumulative-opportunity measure is most ideal when there is a strict limit on acceptable travel time or distance. For example, emergency services that must be reached within 10 minutes. In addition, cumulative-opportunity measure is useful when you are working with policies or regulations that specify maximum acceptable travel times that is needed which can be helpful to identify areas lacking essential services within a critical threshold.

How the cumulative-opportunity measure works:

1. Setting a Cutoff: Decide on a travel time or distance limit, like 30 minutes by bus.
2. Counting Opportunities: Count all the places (jobs, schools, parks) you can reach within that limit.

Limitations of Cumulative-Opportunity Measure:

• Ignores Small Differences: Cumulative-opportunity measure literally assumes that most people do not really care about small differences in travel times or distances(10 min vs. 12min)- arbitrary Cutoffs. As long as the options are within certain limits(the cuff off points), people are generally okay with them(arbitrary Cutoffs).
• Equal Weighting: It also treats all opportunities the same, even if some are more important or harder to reach. There is no gradual decline or weighting; it is an all-or-nothing approach.

This measure is like the cumulative-opportunity measure but offers more in-depth into reaching opportunities. The gravity measures of spatial accessibility consider not just how many places you can reach, but also the attractiveness of the destinations- that is how big and important the place is (like a large hospital vs. a small clinic). It gives more weight/importance to places that are closer and much easier to reach. They are most useful because they can adjust for different types of destinations and how people value those destinations. For example, people might be willing to travel further to a hospital than to a clinic because the hospital offers more services or because of substantial evidence of quality (e.g., patient care quality). How the Gravity Measure works:

1. Distance Decay Function: Distance decay is a concept that describes how the significance of a location diminishes as the distance from it increases. This idea offers an alternative approach for addressing the fact that certain travelers or segments of the population are willing to tolerate longer travel times than others. Various formulas, such as exponential, fixed_exponential, linear, or logistic, are used to comprehend how people's willingness to travel is influenced by distance.
2. Weighted Opportunities: Closer and more attractive places have a bigger impact on the accessibility score.

Limitations of Gravity Measure:

• Complexity: Requires more data and understanding of the factors that influence accessibility.
• Setting Factors: Deciding how much distance affects accessibility (the impedance factor) can be challenging.

• Coordinates: Latitude and longitude of starting points and destinations.
• Geographic Units: Use of centroids from census tracts, blocks, or custom grid cells.

• Public Transit: Buses, trains, subways.
• Active Transportation: Walking, cycling.
• Private Vehicles: Cars, motorcycles.

• Departure Time: The time at which the journey starts, affecting transit schedules and traffic conditions.
• Time Windows: Specified periods during which the analysis is conducted, such as peak or off-peak hours.

• Cutoff Times: Maximum acceptable travel times (e.g., 30 minutes) to consider opportunities accessible.

• Decay Functions: Mathematical functions that model how the likelihood of accessing an opportunity decreases with increasing travel time or distance (e.g., exponential, logistic functions).
• Weights: Assigning importance to opportunities based on travel time, cost, or other factors.

• Transit Schedules: Timetables for buses, trains, and other transit services.
• Road Networks: Maps of streets and pathways, including attributes like speed limits and road types.
• Walking and Cycling Paths: Inclusion of pedestrian walkways and bike lanes.

• Frequencies: How often transit services run.
• Capacities: The number of passengers that can be accommodated.
• Costs: Fares or expenses associated with different modes of travel.

• Walking Speeds: Average or specific walking speeds to account for different populations.
• Transfer Penalties: Additional time or inconvenience associated with changing transit modes or lines.
• Accessibility Needs: Considerations for people with disabilities or mobility challenges.

• Barriers: Physical obstacles like rivers, highways, or restricted areas.
• Topography: Elevation changes that may affect travel times and modes.

• Zoning Regulations: Areas where certain types of development are permitted or restricted.
• Environmental Constraints: Protected areas where development or transit infrastructure is limited.