Troy has two ordinances that apply to your question. Our Temporary Merchant ordinance regulates food trucks. Our Solicitations ordinance regulates ice cream trucks. The distinction is that food trucks are usually stationary in a parking lot whereas ice cream trucks typically are roaming the city.
Here are the links for the chapters on Troy's website:
Temporary Merchant Businesses: http://troymi.gov/Portals/0/Files/C.../CH061.pdf