This study provides new evidence on changes in a range of online activities due to the Coronavirus disease (COVID-19) pandemic. Online activities replaced physical participation in activities and contributed to changes in urban mobility during the pandemic. Using data from a nationwide survey in Greece, the paper examines changes in the importance and the frequency of engaging in online activities before and during COVID-19. Findings show that both the importance and the frequency of engaging in telework, teleconferencing, online learning (e-learning), telehealth, and online shopping (e-shopping) significantly increased during COVID-19 compared to pre-COVID-19. Substantial increases in importance were reported for telework (31% increase), teleconferencing (34% increase), online learning (34% increase), and telehealth (21% increase). Those who, on a daily basis, teleworked, teleconferenced, and made video calls with family or friends quadrupled during COVID-19, while daily online learners increased seven-fold. Telehealth and online shopping also increased but more modestly. Urban mobility in the post-COVID-19 era is likely to depend on the degree of prevalence and acceptance of these remote online activities, together with a set of complex and interconnected factors related to urban form, the spatial planning and decision-making system, and social awareness about the future of cities.

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The improvement of the urban microclimate in the densely-built central areas of Mediterranean cities should be a key objective of integrated urban and transport planning and design in accordance with the UN Sustainable Development Goals on energy, sustainable cities, and climate action. The urban climate of cities in warm regions, already burdened by the urban heat island effect, is expected to worsen further due to the global climate crisis. This study investigates the performance of common environmental street design strategies on microclimate, thermal comfort, and air quality under extreme heat conditions in the Mediterranean city of Thessaloniki, Greece. A typology of streets was selected using criteria such as road functional classification and orientation, land uses, building height/street width ratio, the sky view factor, and the continuity/discontinuity of buildings. A conservative scenario (use of cool/photocatalytic and porous materials for sidewalks, lighter pavements, additional tree planting, installations of green roofs) and a radical scenario (pedestrianization and total traffic prohibition) of environmental design interventions were simulated using the ENVI-met 5.1 software. The research findings demonstrated that the car-free interventions combined with the use of environmentally friendly materials in the public realm could significantly reduce the heat island effect and mitigate gaseous pollutants. The perceived air temperature (Physiological Equivalent Temperature—PET index) can decrease by up to 15 °C in well-shaded locations and near building corners, while nitrogen oxides can be reduced by up to 87% when considering a more radical pedestrianization scenario. The standardization of environmental interventions following a typology of urban streets could support planners and decision-makers in detecting the appropriate solutions for improving the urban microclimate.