The new mirrors are required only for commercial vehicles weighing at least 26,000 pounds that operate on the streets of New York City (with the exception of expressways) and are registered in the state of New York.
The mirrors allow the driver to see any person at least 3 feet tall that is crossing the front of the vehicle at least 1 foot away. These same mirrors have been a requirement for school buses since the 1970s.
When we reported on the proposed law in July, not everyone was happy about the future requirement. In our article, a spokesperson for The New York State Motor Truck Association said the effectiveness of the mirrors decreases when a vehicle is in motion, and the majority of truck accidents occur when a truck is moving.
Some truck rental companies in areas surrounding New York City were also unhappy with the law because even though their companies weren't based out of the city, their trucks might end up in Manhattan, and the mirrors would then be required.
The legislation for the law can be found here: http://open.nysenate.gov/legislation/bill/S3151-2011