Researchers and transit experts have attempted to quantify the “minimum” population density required to justify light rail service in an urban area. Published research suggests somewhere around 19,000 people per square mile (ppsm) within the service area of a light rail system. Noted transit expert Christof Spieler describes a “tipping point” between 10,000 to 15,000 ppsm, at which neighborhoods generate enough trips to justify a higher-capacity transit mode and are complemented by a walkable urban form that discourages driving.
Only two of the St. Louis MetroLink’s 38 light rail stations are located in areas that fall within Spieler’s range, and none meet the threshold identified by researchers.
This doesn’t mean MetroLink was a bad investment—if anything, it’s a success story. The system smartly reused existing rights-of-way and underground infrastructure, allowing it to be built for a relatively low cost. It connects the region’s largest job centers and activity hubs, including Downtown, Clayton, three major universities, and the airport. Between Clayton and Downtown, the light rail is the spine of the Central Corridor, the city’s fastest-growing area, supporting hundreds of millions of dollars in transit-adjacent development. MetroLink is an asset for the region—one that should be utilized to its fullest potential.
St. Louis has an opportunity to differentiate itself from peer Midwestern metros by concentrating development around its high-frequency, fixed-route transit corridor. All new development is beneficial for the city, which urgently needs additional tax revenue, but development within walking distance of MetroLink is the holy grail of infill. In addition to the standard revenue benefits, MetroLink-adjacent development punches well above its weight by supporting the city’s sustainability and equity goals and maximizing the region’s return on its investment in transit. Second only to improvements in the bus network, transit-oriented development is key to increasing MetroLink ridership and strengthening the case for further investment in the system.
The MetroLink walkshed
MetroLink’s Red and Blue lines extend 46 miles across St. Louis County, the City of St. Louis, and St. Clair County in Illinois. The east-west breadth of the system covers a wide range of settings, from the urban heart of Downtown St. Louis to undeveloped fields near MidAmerica Airport. Without any formal analysis, it’s evident that across stations there’s wide variation in the population that lives within walking distance—and many stations serve almost nobody. Putting numbers to these observations will help calibrate our understanding of the system. How many people live near the system today? How much opportunity exists to populate its service area? Which stations stand out as particualrly good or bad?
Researchers and planners have generally found that people will walk up to half a mile to use fixed-route, high-frequency transit. Therefore, MetroLink’s “walkshed” is approximately the area within a half-mile walking distance (not as the crow flies) of the system’s stations. The size of a station’s walkshed is a function of the surrounding street network. Given a fixed walking distance, a station located within a dense grid of small, rectangular blocks will be quicker to access from any nearby point than a station on the side of a freeway in the suburbs, where streets are winding and intersections are few and far between.
Using basic QGIS tools and public data from the Census and Bi-State Development, I generated walksheds for each of MetroLink’s 38 stations. For each station, QGIS’s algorithm traced half-mile-long lines along the street network radiating from the centerpoint of the station. A separate tool converted this web of walking paths into a convex area. I then overlaid these polygons with Census blocks—a geographic unit that is typically coextensive with a city block—to obtain the population living within the walkshed.
Overall, about 45,000 people live within a half-mile walking distance of a MetroLink station. MetroLink’s direct service area covers about 12.7 square miles, or just 1% of the combined land area of the system’s three constitutent counties. The population density of the system’s direct service area is about 3,500 people per square mile—not even one-fifth of the density researchers have found is required to support high-frequency light rail service.
That sounds depressing, but the breakdown by station paints a more interesting picture. All thirteen MetroLink stations located in the City of St. Louis are represented in the top half of stations by population, with the Downtown stations capturing the greatest number of people. Belleville is the only station in Illinois represented in the top half, indicating that the system’s long exurban extensions into St. Clair County are a significant drag on the density of its service area.
This suggests MetroLink’s alignment is better-calibrated than one might assume from surface-level numbers. The segment of the system with the highest level of service, served by both the Blue and Red lines, generally coincides with the most populated areas.
Density, ridership, and opportunity
Walkshed population is just one variable that explains how well a station is utilized. Job density, the presence of major activity centers (e.g., airports, stadiums, tourist attractions), intersecting transit service (e.g., bus lines), and the quality of pedestrian infrastructure are other significant contributors. Given the number of confounding variables, we shouldn’t necessarily expect a strong, clean relationship between walkshed population and station ridership.
However, we can use walkshed density as a crude proxy for the “urbanity” of a station’s surroundings, capturing a large portion of the aforementioned variables. Places with high population density generally have better pedestrian infrastructure, more businesses, schools and other destinations, and a higher overall level of transit service. Plotting average weekday ridership against walkshed population density, we see a few patterns emerge:
The vertical and horizontal lines on the graph indicate the median walkshed density (~3,140 people/sq. mi.) and ridership (~890 riders per weekday), respectively. Segmenting the stations into quadrants based on these midpoints allows us to broadly categorize their ridership performance relative to expectations based on the surrounding population density:
- With low density and ridership, “room to grow” stations (12 total) suffer from their surrounding land use. While the decision to build light rail in many of these areas was questionable, they do present an opportunity to build new transit-oriented housing on mostly blank slates.
- “Exceeds expectations” stations (7 total) punch above their weight given the surrounding land use. Many of these stations are suburban bus terminals (e.g., North Hanley, Fairview Heights, Rock Road), indicating the importance of MetroBus to improving utilization of otherwise far-flung stations.
- “Underperformers” (7 total) have about the same ridership as the system’s most suburban stations despite relatively dense surroundings. These stations are the most challenging to assess—some combination of factors is hampering MetroLink’s attractiveness in otherwise favorable settings.
- Finally, the “exemplary” stations (12 total) benefit from their dense surroundings. We should look to these stations for lessons on what makes transit effective in a city like St. Louis. The two best-performing stations, Central West End and Forest Park–DeBaliviere, are sigificant outliers that merit closer examination.
The crown jewels of the Central Corridor
The heart of MetroLink is the Central West End station, which sits at the center of the Washington University Medical Campus, a conglomeration of hospitals and schools that hosts 26,000 employees. Covering just shy of 190 acres, the campus’s employment density is about 90,000 jobs per square mile—i.e., more than enough activity to support transit service.
Medical centers like the WashU Medical Campus are bread-and-butter features of many American light rail systems. In Houston, a large portion of METRORail’s ridership is generated by the Texas Medical Center, a massive complex with over 100,000 employees. Like central business districts and universities, these dense “activity centers” are some of the only places in the typical large U.S. city that are naturally suited for transit.
Still, the Central West End station does more than ferry hospital employees in and out of a complex with expensive parking. The station’s main entrance is on a pedestrianized segment of Euclid Avenue. Walk five minutes north and you’re at the foot of Euclid’s main drag through the heart of the Central West End, one of the densest and most pedestrian-friendly corridors in the city. Few places in St. Louis do more to discourage driving and make transit the preferable option.
Similar spatial forces are at play one station to the west, at Forest Park–DeBaliviere. Nestled under the intersection of Forest Park Parkway and DeBaliviere Avenue, the MetroLink station sits at the foot of a dense, walkable corridor along DeBaliviere, recently invigorated by the construction of multiple transit-oriented apartment buildings. A short walk from the station, Pershing and Waterman Boulevards are lined with dozens of large multifamily buildings. The station’s northern surroundings are naturally suited to transit, compensating for the lack of density to the south.
The key takeaway from these two stations is that a good transit stop drops you in the middle of things. It places you mere steps from a large number of homes, businesses, and amenities. This is, of course, the core principle of transit-oriented development. It’s the magic behind the New York CIty Subway, where you find yourself surrounded by activity the moment you ascend the stairs from the station.
This is a banal observation, but the majority of MetroLink’s stops are not positioned with this principle in mind—even in relatively dense areas.
MetroLink’s Blue Line extension in St. Louis County is a good idea on paper. The line links a number of activity centers with appreciable population or job density, including downtown Clayton, the St. Louis Galleria, and Maplewood. Yet its stations are consistent underperformers, failing to attract many more riders than semi-rural stations in Illinois. University City–Big Bend is a particularly severe example: despite having the fourth highest walkshed population, the station attracted only 486 riders on an average weekday in 2018, by far the fewest of the ten most populated stations.
A closer look at the station’s surroundings reveals a challenging environment for transit. The station’s walkshed population is high because its surroundings are exceptionally residential, with little vacant or nonresidential land use characteristic of many other stations in the system. However, this housing is predominately single-family, creating an environment where driving is convenient. Few will spend the time or make the effort to walk to the station, past unengaging rows of single-family homes, when their car is easily accessible in the driveway.
Unviersity City–Big Bend and nearby stations also suffer from suboptimal demographics for high transit ridership. In line with the predominance of single-family homes, this part of University City is quite wealthy, with a median household income exceeding $100K. Wealthier households are more likely to own multiple cars, are less sensitive to the costs of car ownership, and place a higher value on their time. A higher level of transit service is required to coax them from their cars.
These characteristics apply to most of the stations on the Blue Line extension. It’s not impossible for light rail to succeed in wealthier, more suburban places like central St. Louis County, but generating ridership requires a more thoughtful strategy than “build it and they’ll come”.
The bus must walk before the train can run
I started this post talking about the poor land use surrounding most of MetroLink’s stations. It’s fairly easy to demonstrate that most of MetroLink’s service area does not meet well-established density thresholds for strong transit ridership. Encouraging transit-oriented development is a no-brainer strategy for the city and Bi-State Development—there is plenty of opportunity to add housing near stations, as long as zoning regulations are loosened and incentives are properly aligned. However, this is the slow path to increased ridership; new development will take years to materialize, and there are significant political barriers to intensifying land use in many areas.
We cannot look solely to land use to cure Metro’s woes, nor can we rely solely on MetroLink to provide a comprehensive transit system for the region. Much of St. Louis’s transit discourse ignores the role of MetroBus, despite the bus system carrying nearly twice as many riders as MetroLink on a typical weekday in 2019. Commenters often pontificate about extensions of MetroLink further into St. Louis County and out to St. Charles, as if slow, expensive, circuitious light rail service to far-flung suburbia would be of practical use to anybody. MetroLink’s existing service in Illinois demonstrates this isn’t the case—pouring capital dollars into expanding the system’s geographic reach will not produce a meaningful shift from driving to transit, nor will it significantly benefit existing riders.
The framing of MetroLink as the region’s only legitimate form of public transportation is undoubtedly reflective of the bus’s lower status, even (perhaps unconsciously) in the minds of self-identifying liberals. In the popular imagination, the train represents revitalization, high technology, speed, and “big city” pedigree, while the bus is lumbering, old-fashioned, and obscure. This sentiment has helped keep federal support for transit restricted to capital expenditures, leaving high-opex bus systems scrounging for resources and producing transit networks that are over-built and under-serviced. (This is the very framework that made the maligned Loop Trolley possible.)
The region must recognize that MetroLink cannot succeed without a strong bus network. As mentioned earlier, this conclusion is supported by the ridership data: outlying stations that also serve as bus terminals punch well above their weight given their low surrounding population density. It’s also in line with international best practices. With similarly suburban development patterns and rates of car ownership, Canadian and Australian cities are the best benchmarks we have for transit system implementation—and they have achieved much higher per-capita ridership than comparable American cities by using extensive, high-frequency bus networks to ferry passengers to rail lines. Calgary (below) and Perth are two particularly instructive examples, with populations and densities comparable to St. Louis.
The answer is actually quite simple; good service (as often as every 6 minutes on the CTrain), and some of the best suburban bus service on the continent. Almost everywhere in the city is within a short walk of one bus route or another, feeding thousands of riders into the CTrain pic.twitter.com/5kqO2NrPtN— The Red Line Podcast (@TheRedLine_pod) February 1, 2023
In its current configuration, MetroBus is a poor foundation for MetroLink. The system’s geographic coverage is weak even in the densest areas of the city, with routes restricted to a handful of major arterial roads. Service frequencies are abhorrent, with the busiest lines running only every half hour and many other routes running less than once an hour. No investment in light rail is justifiable with such inadequate service.
The pandemic’s impact on MetroBus is difficult to exaggerate. Like many other American transit systems, Metro is suffering from a severe operator shortage and lacks the institutional dexterity (or strength of leadership) to respond sufficiently. The agency’s admirable 2019 plan to create a high-frequency network feels incredibly distant as post-pandemic service cuts worsen with no end in sight.
Before Bi-State Development begins seeking federal support to build the North-South line, before commenters on r/StLouis demand a Red Line extension to St. Charles County, before St. Louis’s superficially progressive leaders pay more lip service to the ideals of equity and climate action—the bus system must be fixed. There is no hope for public transportation in the city without functional buses; no matter how vibrant MetroLink’s service area becomes, its population is not enough to sustain the light rail system. More people should live near MetroLink—and it turns out the easiest way to accomplish that is for more people to live near a frequent bus line.