On August 18, 2020, Google announced that it would be adding detailed street maps for New York, San Francisco, and London:

Soon, you’ll be able to see highly detailed street information that shows the accurate shape and width of a road to scale. You can also see exactly where sidewalks, crosswalks, and pedestrian islands are located... We’ll start rolling out detailed street maps in London, New York, and San Francisco in the coming months, with plans to expand to more cities over time.

As of November 30, 2020, Google now appears to be testing this detail among a subset of Google Maps users.

The new detail includes real-world road and path widths and rounded street corners, crosswalks, sidewalks, shapes and icons for pedestrian staircases, and an overall increase in vegetation detail (such as strips of grass between roads):

A few more examples...

This new data isn’t just for display—it also appears to be incorporated into Google’s algorithms for walking directions. If you look closely below, you’ll notice that the route line crosses streets at the crosswalks...

...and follows the curves of the sidewalk shapes: