Problem: There is not enough tree canopy, and so temperatures will got hot.
Problem: Cars drive too fast.
Solution: Plant trees in the streets.
As shown in the figures below, Glebe and Haberfield, two of Sydney’s leafier suburbs, have trees planted in the street, using space that would otherwise be vacant most of the time (nominally available for car storage). Some newer areas, like the Bonar Street section of Arncliffe, are doing similar things. It is an excellent way to get more canopy than currently available, reduce travel speed and likelihood of collisions and because of the lowered speed, make collisions less severe, improve mental health and the physical environment. Walking under the canopy of trees is far more pleasant than walking directly under the hot sun, and so people will walk more in that environment. Planting trees also increases property value.
More suburbs should do this.
King Street in Enfield also does this (Google Streetview)