Zoning regulations and districts are herein established in accordance with a comprehensive plan for the purpose of promoting the health, safety, morals and general welfare of the city. They are designed to lessen congestion in the streets; to secure safety from fire, panic and other dangers; to provide adequate light and air; to prevent the overcrowding of land, to avoid undue concentration of population; to facilitate the adequate provision of transportation, water, sewerage, schools, parks and other public requirements. They have been established with reasonable consideration, among other things, for the character of each district, and its peculiar suitability for the particular uses specified; and with a view to conserving the value of buildings and encouraging the most appropriate use of land throughout the city.