The following paragraph explaining the New York City law regarding idling trucks is taken from the New York City Administrative Code (ADC). The complete text of this particular regulation can be found here: http://law.onecle.com/new-york/new-york-city-administrative-code/ADC024-163_24-163.html

The complete ADC can be found on the NY State Legislature's website: http://public.leginfo.state.ny.us/frmload.cgi?MENU-55427175. Click on the "Laws of New York" link at the botttom of this page, then scroll down to the "ADC" link at the bottom of the following page. In order to locate a specific subsection, look at the numbers within the parentheses that follow chapters and subchapter titles.

§  24-163 Operation of motor vehicle; idling of engine restricted.

(a) No person shall cause or permit the engine of  a  motor  vehicle,  other
  than  a  legally  authorized emergency motor vehicle, to idle for longer
  than three minutes while parking  as  defined  in  section  one  hundred
  twenty-nine  of  the  vehicle  and  traffic  law, standing as defined in
  section one hundred forty-five  of  the  vehicle  and  traffic  law,  or
  stopping  as  defined  in section one hundred forty-seven of the vehicle
  and traffic law, unless  the  engine  is  used  to  operate  a  loading,
  unloading  or  processing  device.  When  the  ambient temperature is in
  excess of forty degrees Fahrenheit, no person shall cause or permit  the
  engine  of  a  bus as defined in section one hundred four of the vehicle
  and traffic law to idle while parking, standing, or stopping (as defined
  above) at  any  terminal  point,  whether  or  not  enclosed,  along  an
  established route.

(b)  The  department  of  transportation  shall post signs relating to
  prohibited idling that shall comply with the standards set forth in  the
  Manual  on  Uniform  Traffic  Control  Devices  and,  where practicable,
  include the maximum penalty that may  be  imposed  for  a  violation  of
  subdivision a of this section as follows:  

  [a number of situations are described, including the following:]

    (6)  signs  shall  be posted at other appropriate locations throughout
  the city as jointly determined by the commissioner and the  commissioner
  of transportation, including but not limited to, locations for which the
  city  receives  a  substantial  number  of  complaints  of  idling motor
  vehicles.

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