Shutting down (a small section of) Memorial Drive on Sundays in the summer also seems like a win. There's a parallel road on the other side of the river that can pretty much substitute at a lower traffic time, but you almost certainly wouldn't want to cut that capacity at rush hour on a weekday when both sides of the river are already horrible in terms of traffic capacity.

In a way, getting rid of cars is the special event: increased foot traffic, food vendors, outdoor seating, and other events like markets and live music tend to follow on naturally.

Apart from pedestrian streets, you also see this in well-integrated urban parks and plazas like Union Square, Washington Square, or Bryant Park in NYC.