Transportation is formally recognized as a social determinant of health, and the evidence backing that designation runs deeper than most people realize. The U.S. Department of Health and Human Services includes it within the “Neighborhood and Built Environment” domain of its Healthy People 2030 framework, and the healthcare sector has increasingly invested in addressing transportation gaps as a path to better outcomes. But calling something a “social determinant” can feel abstract. The concrete story involves missed doctor visits, children breathing exhaust near highways, pregnant women unable to reach clinics, and older adults cut off from the social connections that keep them well. Each of these pathways operates through different mechanisms and affects different populations, which is why transportation shows up again and again in public health research.
When People Cannot Get to the Doctor
The most immediate way transportation shapes health is straightforward: if you cannot reliably get to a clinic, you do not get care. Research has documented that transportation barriers lead to rescheduled or missed appointments, delayed treatment, and skipped medications. In one analysis, roughly half of missed appointments or late arrivals were attributed to transportation problems. The downstream effects compound quickly. Patients discharged from hospitals who had difficulty getting to a pharmacy filled prescriptions at far lower rates than those who did not report difficulty, and when Medicaid payments for transportation were restricted, medication refills dropped.1PubMed Central. Traveling Towards Disease: Transportation Barriers to Health Care Access
For people managing chronic conditions like diabetes or asthma, missing even a few appointments or running out of medication can set off a cascade. Blood sugar drifts out of control, symptoms flare, and what would have been a routine office visit turns into an emergency room trip. That pattern has been confirmed by studies showing that when transportation brokerage services were introduced for Medicaid beneficiaries, hospitalizations dropped for asthmatic children and preventable admissions fell for diabetic adults.2PubMed Central. Transportation brokerage services and Medicaid beneficiaries’ access to care
Do Rideshare Programs and Transportation Interventions Fix the Problem?
Given the clear link between transportation barriers and missed care, you might expect that providing free rides would solve things. The reality is more complicated. A meta-analysis pooling seven studies found that transportation interventions did reduce missed appointments, with about a 37% lower rate of no-shows compared to controls.3PubMed Central. Effect of interventions for non-emergent medical transportation: a systematic review and meta-analysis That sounds promising, but the evidence on whether those kept appointments translated into better health outcomes was too thin to draw conclusions.
When researchers tested rideshare-based solutions specifically, results were even less encouraging. A clinical trial offering free rideshare trips to primary care patients found that only about a quarter of those offered the service actually used it, and the missed appointment rate was virtually identical between the intervention group and the control group.4PubMed Central. Association of Rideshare-Based Transportation Services and Missed Primary Care Appointments: A Clinical Trial A separate study at an academic medical center found no significant difference in missed MRI appointments after implementing a rideshare program either.5PubMed Central. Analysis of the Effects of a Patient-Centered Rideshare Program on Missed Appointments and Timeliness for MRI Appointments at an Academic Medical Center
Why the disconnect? A systematic review of transportation interventions noted that most rigorous studies showed low patient uptake and inconsistent impacts on utilization. Part of the problem is that missing an appointment is rarely caused by transportation alone. People face overlapping barriers: work schedules, childcare, distrust of the healthcare system, phone and internet access needed to book rides, and mental health challenges that make it hard to follow through on plans. Handing someone a ride addresses one layer but may not be enough when multiple layers are stacked. The Iowa Medicaid experience illustrated a related issue: awareness of available transportation benefits was low, and the populations eligible for non-emergency medical transportation had higher overall vulnerabilities, which blunted the benefit’s impact.6PubMed Central. Transportation barriers for Iowa Medicaid-enrolled adults with and without non-emergency medical transportation services
Traffic Pollution and Children’s Lungs
Transportation does not just affect health by limiting access to care. The transportation system itself is a source of disease. Traffic-related air pollution (TRAP) is one of the strongest environmental pathways, and children are especially vulnerable. A large study of children in Southern California found that those living near busy roads had roughly 50% higher risk of developing asthma compared to children with lower exposure to traffic pollution near their homes, with a similar elevation for pollution exposure near schools.7PubMed Central. Childhood Incident Asthma and Traffic-Related Air Pollution at Home and School Another study found that children living within about 75 meters of a freeway had roughly double the odds of current asthma compared to those in the lowest-exposure areas.8PubMed Central. Residential Traffic and Children’s Respiratory Health National-level modeling has worked to quantify the total burden of childhood asthma attributable to TRAP across the United States.9PubMed. Traffic related air pollution and the burden of childhood asthma in the contiguous United States in 2000 and 2010
The damage goes beyond respiratory disease. Traffic noise and exhaust both contribute to cardiovascular risk in adults through overlapping biological pathways, including stress hormone elevation, disrupted sleep, vascular inflammation, and oxidative stress.10PubMed Central. Noise and Air Pollution as Risk Factors for Hypertension: Part II-Pathophysiologic Insight A review in Nature Reviews Cardiology described how nighttime traffic noise fragments sleep and raises stress hormones, promoting vascular dysfunction and hypertension over time.11Nature Reviews Cardiology. Transportation noise pollution and cardiovascular disease In other words, living near a major road can quietly increase your blood pressure and heart disease risk even if you never set foot in a car.
Getting to Groceries
Food access is another health pathway shaped heavily by transportation. In neighborhoods classified as food deserts, the absence of a grocery store within walking distance forces residents to rely on transit to buy fresh food. And that transit is often inadequate. An analysis of several U.S. cities found stark differences: in some metro areas, nearly half of food desert addresses had no bus stop within three-quarters of a mile, and in Raleigh, North Carolina, 44% of food deserts had zero grocery stores reachable within 30 minutes by public transit.12PubMed Central. Connecting People to Food: A Network Approach to Alleviating Food Deserts
When transit options disappear, diet quality follows. Research tracking what happens after public transportation routes are cut from urban food deserts found that lower-income households made fewer trips to grocery stores and more trips to dollar stores and drug stores. The shift showed up in purchasing data: fewer healthy foods, more unhealthy ones.13Journal of Regional Science. Public Transportation Access and Food Insecurity A separate geographic analysis found that people who are lower-income, non-White, older, or disabled are more likely to depend on buses for food shopping, and in less urban areas, bus access to affordable healthy food was effectively nonexistent.14PubMed Central. Transit bus access to healthy, affordable food
Prenatal Care and Birth Outcomes
The consequences of transportation barriers during pregnancy are severe enough to deserve separate attention. A scoping review of studies focused on Black and African American women found that lack of reliable transportation contributed to delayed initiation of prenatal care, missed appointments, and the need to reschedule visits in the majority of studies reviewed.15PubMed Central. Transportation Barriers to Prenatal Care Among Black/African Americans: A Scoping Review And those missed visits have real consequences for newborns. A study of women who received no prenatal care found they had significantly higher rates of preterm birth even after adjusting for demographic differences. Those same women lived in areas with longer transit times to clinics, averaging about 42 minutes compared to 30 minutes for women who did receive care.16PubMed. Geographic barriers to prenatal care access and their consequences
Distance matters in a dose-response fashion. A regression analysis found that every doubling of travel distance to a prenatal provider was associated with lower odds of initiating care on time and fewer total visits.17PubMed Central. The association of travel burden with prenatal care utilization, what happens after provider-selection This is not an abstract concern: preterm birth carries lifelong health consequences, and it is one of the leading contributors to infant mortality in the United States.
Who Gets Hit by Cars and Why It Is Not Random
Transportation infrastructure does not just move people; the physical design of roads determines who is safe walking in their own neighborhood. Pedestrian fatalities and serious injuries fall disproportionately on communities of color and lower-income areas, and the pattern traces back decades. An analysis of Chicago found that Black-majority neighborhoods, representing about 24% of the city’s population, accounted for 37% of severe pedestrian crashes.18PubMed. How racial segregation contributes to disparities in pedestrian safety An Oregon study found similar patterns: lower median income and higher proportions of BIPOC residents were associated with more pedestrian injuries, likely reflecting decades of underinvestment in sidewalks, crosswalks, and traffic-calming infrastructure.19Transportation Research Part D: Transport and Environment. Race and income disparities in pedestrian injuries
The historical roots run even deeper. Researchers mapped pedestrian fatality data from 2010 to 2019 against the federal government’s 1930s-era redlining maps and found a clear dose-response relationship: neighborhoods that had been graded “D” (labeled “Hazardous,” overwhelmingly communities of color) had a pedestrian fatality rate about 2.6 times higher than neighborhoods graded “A.” As the redlining grade worsened from A through D, pedestrian death rates climbed at each step.20PubMed Central. Structural Racism and Pedestrian Safety: Measuring the Association Between Historical Redlining and Contemporary Pedestrian Fatalities Across the United States, 2010‒2019 This is transportation as a social determinant in its starkest form: where a road was built, how fast traffic moves, and whether sidewalks exist are life-and-death decisions that were shaped by racial policy nearly a century ago and still kill people today.
Rural Distance and the Erosion of Access
In rural areas, the transportation barrier is physical distance itself. A scoping review found that the vast majority of studies on distance and healthcare access focused on specialist services, where the consequences of long travel are most visible. “Distance decay” in healthcare use, meaning people simply stop seeking care as trips get longer, was documented at distances as short as a few kilometers for routine visits and as far as 90 to 100 kilometers for specialist services like cancer treatment and psychiatric care.21Journal of Transport & Health. Impact of distance and/or travel time on healthcare service access in rural and remote areas: a scoping review
A cross-sectional study of older adults in the northeastern United States found that longer travel times to healthcare were associated with lower mental health scores and a higher burden of chronic disease, including increased odds of cancer and diabetes. Each additional 10 minutes of travel time was linked to a measurable drop in mental health scores.22PubMed Central. Evaluating the Connection Between Rural Travel Time and Health: A Cross-Sectional Analysis of Older Adults Living in the Northeast United States Rural patients also traveled farther for emergency care than their urban counterparts, adding time pressure to situations where minutes matter.23PubMed Central. National travel distances for emergency care
Older Adults, Disability, and Isolation
For older adults who no longer drive and people with disabilities, transportation is not just about healthcare access; it shapes whether you leave the house at all. A study of public transportation barriers experienced by people with disabilities found that a majority of respondents had difficulty accessing public transit, and that community activities without fixed schedules were hit hardest because paratransit services typically require advance booking.24PubMed. Community participation and public transportation barriers experienced by people with disabilities When spontaneous social outings become logistically impossible, isolation sets in.
On the flip side, well-designed transit systems can act as a buffer against loneliness. A natural experiment in Hong Kong found that the opening of a new metro line helped older women strengthen their social networks and reduce social isolation and loneliness, particularly among those who were already socially active at baseline. The key word there is “well-designed”: a system that is physically accessible, runs frequently, and connects to places people want to go.25PubMed. Gendered impacts of public transport on social isolation and loneliness among older adults Social isolation is itself a major health risk factor, comparable in magnitude to smoking or obesity, so the connection between transit availability and loneliness has real physiological consequences.
Active Transportation and the Built Environment
Transportation systems can harm health, but they can also promote it when they are designed to support walking and cycling. A systematic review of active travel interventions found consistent co-benefits beyond just increasing physical activity: about 70% of relevant studies showed improved safety outcomes, two-thirds showed improved health, and large majorities found economic and environmental benefits as well.26PubMed. The co-benefits of active travel interventions beyond physical activity: a systematic review A cross-national comparison found that countries with the highest rates of walking and cycling generally had the lowest obesity rates, and that Europeans walked and cycled substantially more than Americans.
The obesity connection is more nuanced than simply “walk more, weigh less.” A study of adolescents across eight countries found that walking for transportation was not significantly associated with lower obesity rates, but cycling for at least 10 minutes per week was linked to a modestly lower likelihood of being overweight or obese.27PubMed Central. Walking and cycling, as active transportation, and obesity factors in adolescents from eight countries The distinction matters for urban planning: building bike infrastructure may deliver more health benefit per dollar than simply making sidewalks wider, though both contribute to a more walkable and bikeable environment.
Redlining, Highways, and Persistent Environmental Injustice
Many of the health harms tied to transportation infrastructure are not distributed evenly because they were never meant to be. Neighborhoods graded C or D on the federal government’s 1930s redlining maps, grades assigned primarily on the basis of racial composition, continue to have consistently higher exposures to fine particulate matter and nitrogen dioxide, with no meaningful narrowing of the gap over the past several decades.28PubMed Central. Historical Neighborhood Redlining and Contemporary Environmental Racism Highways built through these same neighborhoods during the mid-twentieth century compounded the problem, concentrating exhaust, noise, and crash risk in communities that were already marginalized. Researchers have noted that cities like Oklahoma City, Cincinnati, and Albany share histories of racialized zoning and highway construction that helped create conditions for cumulative environmental injustice.29Environmental Science & Technology Letters. Historical Redlining and Cumulative Environmental Impacts across the United States
This intersection of transportation policy and racial history helps explain why calling transportation a social determinant of health is not just a label. It is a recognition that infrastructure decisions, from where highways get routed to which neighborhoods receive bus service, carry health consequences that persist for generations. The children breathing traffic exhaust near a freeway in a formerly redlined neighborhood are living with the health effects of decisions made before their grandparents were born.
When Extreme Weather Shuts Down Transportation
Climate change adds a newer dimension. As extreme weather events become more frequent, the transportation systems that people depend on for emergency care become unreliable precisely when they are most needed. A five-year study of motorcycle ambulance services in a resource-limited setting documented sharp declines in operational availability during heavy rain and extreme heat. Ambulance availability dropped from about 81% to 34% during these conditions, even as demand for emergency responses more than doubled over the study period.30PubMed Central. Climate Extremes and Healthcare Access: Assessing the Impact of Severe Weather Events on Emergency Motorcycle Ambulance Availability While this particular study focused on motorcycle ambulances, the broader lesson applies everywhere: heat waves buckle rail tracks, floods close roads, and ice storms ground transit systems. In communities that already have fragile transportation networks, climate disruption can turn a chronic access problem into an acute emergency.