Over the past few years, transit agencies across the U.S. have seen stagnating or declining bus and rail ridership. This is concerning, as the transportation sector is the single largest contributor to greenhouse gas emissions and transit is key to reducing air pollution, promoting equity, and providing accessibility to transit-dependent communities. So, what is causing this decline in ridership?
Mobility Lab just published a study examining this question for Arlington County – or Arlington Transit (ART) – by looking at the determinants and barriers of ridership. Much of the research was guided by a literature review of pertinent studies on bus and transit ridership. Here is our summary of the review.
Broadly, three categories of factors can determine bus ridership:
- The transportation system and the built environment. This includes variables considered “internal” to transit systems; like fares, service level, and real-time information; as well as “external” variables; like the existence of competitive modes and land use patterns.
- Transportation users. This group of research discusses factors related to transportation demand, including demographics and user perception.
- External factors. This includes things that transit agencies and city planners can’t control, like the weather and the state of the economy, that are found in the literature to have a substantial impact on bus ridership.
What are the most important factors within these groups? And what impact does the literature suggest they have on bus ridership?
The transportation system and the built environment
Fare cost, a system’s level of service, and the availability of real-time information are all found in the literature to influence bus ridership. Increased fares are found to decrease ridership levels: studies find that a 10% increase in fares can decrease bus ridership anywhere from 2-4% (Pham & Linsalata, 1991; and Boisjoly et al., 2018). A system’s level of service – factors related to route frequency, route coverage, and route speed – are unsurprisingly found throughout the literature to be positively correlated to ridership. However, researchers find that there is a diminishing marginal return on service level improvements, meaning that improving service on a low-frequency or low-coverage route will have a greater impact than changes to an already high performing route. The literature also finds that real-time information, or bus tracking technology that delivers information about a bus’s real-time schedule, is linked with higher ridership. Mobility Lab’s recent study on real-time transit information in Arlington County found that access to accurate real-time bus arrival information impacts mode choice, because it helps travelers weigh factors of cost, convenience, and time as well as improves the perceived reliability of transit.
Research also finds that the existence of competitive modes (such as Uber or bikeshare) and land use patterns impacts bus ridership. In terms of land use, research finds that generally denser urban environments and street design that prioritizes buses and walking over private automobiles are associated with higher levels of bus ridership. Findings on the impact of competitive modes is not as conclusive. Research on the impact of Transit Network Companies (TNCs) such as Uber and Lyft are mixed; some studies find that the introduction of TNCs leads to reduced bus ridership (Graehler, Mucci and Erhardt, 2019), while others find that on average, TNCs have a complementary effect on transit systems (Hall, Palsson, and Price, 2018). Studies on the impact of bikeshare and bike infrastructure are similarly divided. Although research on e-scooters and other dockless mobility systems is currently limited, recent studies (including a recent Virginia Tech study) suggest that e-scooters are more likely to replace car trips than public transit trips. Mobility Lab’s recent study evaluating the shared mobility devices pilot program in Arlington County finds that only 3% of e-scooter or dockless e-bike riders substituted these trips for bus trips.
Research on bus ridership finds that certain groups of people are more likely to ride the bus than others, and that perceptions and attitudes towards buses also impact ridership. In general, studies find that immigrants, racial minorities, lower-income populations, and younger generations are more likely to ride the bus. New research on the shifting travel patterns of Millennials and younger age groups suggests that Millennials are more multi-modal and less likely to get their driver’s license at a young age than other age groups. These changes may be due to macro-economic conditions (e.g., the Great Recession’s impact on the costs of car ownership), life-stage changes, and changing attitudes about transportation modes (e.g., environmental consciousness). The impact of perceptions and attitudes on bus ridership is increasingly studied in the literature; safety, comfort, convenience, loyalty to a transit system, and pro-environmental attitudes are all associated with satisfaction with transit service and ridership levels.
Unsurprisingly, adverse weather such as rain, snow, or extreme temperatures have a large impact on bus ridership. However, measures that decrease the amount of time that people must wait for the bus while exposed to the elements may decrease this: bus shelters, accurate real-time transit information, and increased service level may all help transit agencies to prevent lost ridership in inclement weather.
Economic conditions explain a lot of bus ridership changes, according to the literature. When the economy is strong, as it has been in recent years, research finds that overall increased incomes make it easier for people to own and use cars. Economic recessions may also negatively impact transit ridership; for example, Taylor and McCullough (1998) find that the recession in the early 1990s was correlated with decreased public transportation ridership nationwide as systems suffered from budget and service cuts.
So, in summary, what can we learn from the literature about bus ridership trends?
It is difficult to determine a ranking of the factors that impact bus ridership across the literature, as each study we reviewed uses different factors and methodologies to analyze bus ridership. Also, certain ridership determinants (such as cost) are more heavily researched than others (such as perceptions), skewing our current understanding of bus ridership. However, as research on the under-studied aspects of bus ridership progresses – such as research on TNCs, new mobility modes, and perceptions and attitudes towards transit – we will hopefully be able to better understand the full suite of factors that impact bus ridership.
Comparing our literature review to recent reports on declining ridership, such as TransitCenter’s 2019 Who’s on Board report, it is clear that car dependence impacts bus ridership. The choice between taking the bus and a car in fact depends upon many of the variables discussed here, such as perceptions like bus stigma or environmental consciousness, the affordability of driving versus transit, and the convenience of taking transit versus a car, which is largely influenced by land use and service level.
Buses are a vital component of a sustainable, equitable transportation grid – they are more flexible than rail, they are affordable, and they cut back carbon emissions and air pollution by reducing the need for private vehicles. As such, building a better understanding of why people choose buses over other modes or vice-versa is crucial to reversing trends of reduced bus ridership. Mobility Lab’s newest publication fills a gap in this understanding in the context of ART in Arlington County.
References cited here, as well as the full literature review, can be found in our full ART Satisfaction Report (PDF).