Measurements of the Impacts of Neighborhood-Scale Cool Pavement Deployments on Albedo, Temperatures, and Pedestrian Thermal Comfort in the Greater Los Angeles Area

Climate change is expected to exacerbate the urban heat island effect in cities around the world, increasing the public health risk of heat-related illnesses and mortality. Solar reflective “cool pavement” is one of several potential mitigation strategies that has the potential to counteract the negative effects of the urban heat island effect. In short, an increase in pavement albedo results in less heat being absorbed by the pavement, which in turn results in reduced surface temperatures. Near surface air temperatures could also be reduced if cool pavements are deployed at sufficiently large spatial scales, though this has never been confirmed by field measurements. There have been a number of modeling and laboratory studies investigating the heat mitigation benefits of cool pavement, but this study is the first to conduct measurements of the environmental consequences of neighborhood-scale cool pavement installations in the real world. We measured surface temperature, near-surface air temperature, albedo, and thermal comfort both before and after cool pavement installation. In addition, pavement albedo was measured several times after cool pavement installation to assess the extent to which it decreases due to aging after installation. Measurements were taken in the greater Los Angeles area, with three sites (~0.1 km² each) in the San Fernando Valley, California, and at one site in Covina, California (~0.7 km²). Continuous, mobile transect measurements of air and surface temperature were taken over each target area (with cool pavement installed) and a corresponding control area (upwind with no cool pavement), every three hours between 06:00 and 21:00 Pacific Time. Continuous, mobile albedo measurements were taken with an albedometer to assess the effect of weathering on the albedo of the cool pavement. Lastly, mean radiant temperature was measured on the sidewalk in the target areas, both pre-installation and post-installation, to quantify how pedestrian thermal comfort would be impacted throughout the day. Preliminary results show that cool pavement reduces surface temperature by ~3-10 Cº, with the largest reductions generally observed around 03:00 Pacific Time. Cool pavement albedo varied widely, from ~0.10 to 0.27, and we observed a clear decrease in albedo over time. Further analysis will be completed to quantify the effect of cool pavement on air temperature and pedestrian thermal comfort.