Phoenix tried a reflective coating on black asphalt; noon surface heat fell 12°F
(economictimes.indiatimes.com)
I'll quote the relevant passages for you. It describes the results from two different studies.
Study #1:
The research found that mean radiant temperature, a measure of the thermal radiation absorbed by the body outdoors, rose by an average of 5.5°F on the coated streets.
Study #2:
It noted [...] mean radiant temperature over the [coated] pavement rose about 4°C (7.2°F) at midday