In case of a crash involving a pedestrian and a motor vehicle, just a small decrease in motor vehicle speed can mean a dramatic increase in survival rates. A little extra speed has a big impact on pedestrian-rich streets and sidewalks of New York City. For every extra mile per hour of speed:

• Required stopping distance increases
• Required time to react to avoid a crash decreases
• The impact of a crash is more severe on involved vehicles, drivers, passengers and pedestrians

In case of a crash, speeds over 20 mph exponentially increase the likelihood of fatality:

• Hit someone at 40 mph, there is a 70 percent chance they will die
• Hit someone at 30 mph, there is an 80 percent chance they will live
• Hit someone at 20 mph, there is a 98 percent chance they will live

According to the Department of Motor Vehicles, speeding is the number-one cause of deadly crashes in NYC. From the safe speed recommendations of the Safe Routes to School and Safe Streets for Seniors program to Terminal Velocity, T.A.'s seminal study of NYC's speed epidemic, T.A. has been pushing for years to lower the speed of NYC streets.

In the NYC DOT's Pedestrian Safety Study and Action Plan, the City committed to piloting at least one 20 mph zone on a neighborhood-wide basis in 2011. Communities across the United Kingdom have implemented a 20 mph speed limit, and their evidence has shown that even without extensive changes to the roadway, lowering the speed on residential streets is an effective method to calm traffic.

Whether New York City can accelerate and expand the program of reduced-speed zones around schools or learn from the U.K. by introducing lower speed limits in a wider area as a complement to an extensive system of school zones, we must follow the example of our sister cities across the world and start aggressively reducing traveling speeds to less than 20 mph in residential areas.

Run the Pedestrian Injury Simulator to see the impact of speed and various driving impairments upon your thinking and braking distances.