There are symbols of two religions: Hinduism and Sikhism together on the truck for good luck and charm. One of the gods of Hinduism, Hanuman is on the top of the truck and the window pane has Khanda, one of the most important Sikh symbol. This tells you how different religions co-exists together in India for most part. Also, there are two languages on the truck, Punjabi and English.
On "Govt. Duty" means a private truck is subcontracted by the Government. The truck here carries gasoline for Hindustan Petroleum to gas stations.
It is possible that the truck is owned by Punajbi Hindu family, and commonly drivers are Sikhs, or vice versa or something like that. Often shops in India have mixed religious symbols too. It is quite common.