The really dangerous drivers in New York aren't dangerous because they're speeding.
They're really dangerous because they weave in and out of tightly packed traffic trying to find a minuscule gap to wedge themselves into to try and go around everybody.
If anything, being unable to go fast is going to psychologically compel impatient people to take even more risks to make up for time they'll be perceiving themselves as losing due to being limited in speed. Additionally, limiting their car's speed is going to make this process even more dangerous for bystanders because they're not going to have the power available to actually perform these maneuvers.
If you want to focus on public safety, figure out a way to get slow-pokes out of the passing lane who camp there next to a truck for an hour and clump up traffic, and get cops to focus on drivers who wildly weave from lane to lane with no signals.