Comment by thfuran

There are materials that do what you're looking for surprisingly effectively, staying many degrees sub-ambient even in direct sunlight. (See https://onlinelibrary.wiley.com/doi/full/10.1002/eom2.12284 for example). But a roadway is a really difficult use case for a surface coating. With something like 50% of the surface area of many American cities being road or parking, there's a lot of potential room for effectively mitigating the urban heat island effect, but I think roofs are a better target. They don't have cars sitting on top of them blocking sightlines nearly as often.