Who pays the transfer penalty and why? A systematic review of socio-demographic patterns in transit transfer trips

The act of transferring between public transport services remains one of the most significant deterrents to ridership. This paper presents the first systematic review of empirical evidence of how transfer penalties vary by socio-demographic groups. It also explores causal factors which influence these variations. Adhering to PRISMA 2020 guidelines, a systematic search across Scopus, Web of Science, IEEE Xplore and PubMed identified 1,576 records, from which 59 studies were included in the final synthesis. A range of new standardisation methods were developed to enable objective comparisons of transfer penalties and factors influencing them between socio-demographic groups. Evidence is synthesised across five socio-demographic comparator pairs examined in Section 4: gender (women vs men), age (younger vs older), trip purpose (non-commuter vs commuter), income (low vs high), and disability (impaired vs baseline). Transfer penalties are generally larger for women (1.02× to 5.38× men; mean 2.17×), for non-commuters (1.09× to 2.26× commuters; mean 1.63×), and for low-income groups (mean ratio 3.70×); results for age and disability are mixed and hence inconclusive. The literature coverage is uneven, with commuters, gender and age receiving substantial attention, while mobility-impaired users and ethnic minorities remain severely under-studied. Causal factors driving socio-demographic differences in transfer penalties were identified; 10 individual causes grouped into psychological and cognitive factors, physical and environmental factors and operational and spatiotemporal factors were identified. An evidence weighting methodology is developed to synthesise the literature into a consistency matrix encompassing ten causal factor groups and thirteen demographic segments. Transfer duration emerges as the most broadly evidenced factor, while safety-related anxiety shows the strongest gender differentiation. The review highlights that age-sensitive and disability-differentiated design responses are needed at interchange facilities, rather than uniform approaches to accessibility. Implications of the research for future research and practice are discussed.