Today is the third day of New York's new congestion relief zone. And if you're curious to see how it's already impacting traffic conditions, here is a website run by Joshua Moshes and Benjamin Moshes, under the supervision of Brown University Professor Emily Oster.
The site collects Google Maps traffic data every 15 minutes for 19 routes leading into Manhattan (some of which are directly affected by the new relief zone and some of which are not). It then calculates average traffic times for each day of the week, both before and after the congestion charge.
Here is the Holland Tunnel on Sunday (which was day number one):

