Highway expansion accelerates urban heat islands: systemic urban design flaws and policy failures drive thermal inequity

Indigenous land stewardship offers time-tested strategies for heat mitigation, such as the Tohono O’odham’s use of 'washes' (dry riverbeds) to channel cool air and the Māori practice of 'mara kai' (food gardens) interspersed with native trees to reduce urban heat. These approaches prioritize ecological balance over extractive infrastructure, yet they are systematically excluded from urban planning due to colonial land tenure systems and the dominance of Western engineering paradigms. Integrating indigenous knowledge would require ceding decision-making power to Indigenous communities and recognizing their land rights as foundational to climate resilience.

Highway expansion in the U.S. was not an organic urban growth pattern but a deliberate policy choice, codified by the 1956 Interstate Highway Act, which displaced over a million people—disproportionately Black and Latino communities—under the guise of 'urban renewal.' The same era saw the decline of streetcar systems and the rise of car dependency, embedding heat-absorbing asphalt into the urban fabric. Globally, colonial cities replicated this model, with highways slicing through informal settlements to serve elite mobility, a pattern repeated in postcolonial megacities like Lagos and Jakarta.

Cross-culturally, heat mitigation strategies diverge sharply: Mediterranean cities use whitewashed buildings and shaded public spaces, while Middle Eastern cities employ wind catchers and underground aqueducts to circulate cool air. In contrast, U.S. cities rely on energy-intensive air conditioning, which exacerbates the urban heat island effect by dumping heat outdoors. Asian cities like Tokyo have experimented with 'cool roofs' and permeable pavements, but these solutions are often scaled without addressing the root causes of car dependency that drive highway expansion.

Scientific consensus confirms that dark asphalt and concrete absorb and re-emit solar radiation, raising local temperatures by 2–8°C compared to rural areas, with highways acting as 'heat corridors' that channel thermal energy into urban cores. Studies show that highway retrofits—such as reflective coatings, porous pavements, and vegetated medians—can reduce surface temperatures by 3–5°C, though their efficacy depends on regional climate and maintenance. However, most research focuses on mitigation rather than prevention, ignoring the thermodynamic limits of retrofitting car-centric infrastructure.

Artistic and spiritual traditions often frame heat as a metaphor for imbalance or divine retribution, as seen in Islamic art’s use of blue and green to evoke coolness or Hindu temple architecture’s integration of water features for thermal regulation. Contemporary artists like Olafur Eliasson have used light and temperature to critique urban alienation, while Indigenous ceremonies in the Southwest emphasize reciprocity with land to maintain ecological balance. These perspectives challenge the mechanistic view of cities as machines, instead framing heat as a symptom of disconnection from place and community.

Future scenarios must account for the thermodynamic limits of retrofitting highways, as even 'cool' pavements cannot offset the heat generated by vehicle exhaust and tire friction. Scenario modeling suggests that transitioning to 15-minute cities, where daily needs are met within walking distance, could reduce highway-induced heat by 40% while improving public health. However, such models require integrating climate science with social equity metrics, as marginalized communities often lack the political power to resist highway expansion or demand alternative infrastructure.

Marginalized communities—particularly Black, Latino, and Indigenous neighborhoods—bear the brunt of highway-induced heat due to redlining, lack of green space, and proximity to industrial zones, yet their expertise in heat adaptation is rarely centered in policy debates. Grassroots groups like WE ACT for Environmental Justice have documented how highway expansions in NYC and Atlanta exacerbate asthma and heat-related illnesses, but their solutions (e.g., community gardens, shade networks) are dismissed as 'unscientific.' Amplifying these voices requires dismantling the deficit framing of marginalized communities and funding their leadership in urban design.