How does using train as a transport (compared to the use of bus) conserve more fuel?

Public transport (also known as public transportation, public transit, or mass transit) is transport of passengers by group travel systems available for use by the general public, typically managed on a schedule, operated on established routes, and that charge a posted fee for each trip. Examples of public transport include city buses, trolleybuses, trams (or light rail) and passenger trains, rapid transit (metro/subway/underground, etc.) and ferries. Public transport between cities is dominated by airlines, coaches, and intercity rail.

Bus services use buses on conventional roads to carry numerous passengers on shorter journeys. Buses operate with low capacity (compared with trams or trains), and can operate on conventional roads, with relatively inexpensive bus stops to serve passengers. Therefore, buses are commonly used in smaller cities, towns, and rural areas, and for shuttle services supplementing other means of transit in large cities.

Passenger rail transport is the conveyance of passengers by means of wheeled vehicles specially designed to run on railways. Trains allow high capacity on short or long distance, but require track, signaling, infrastructure and stations to be built and maintained.

A train uses more fuel than a bus but it is more profitable because a train has a number of coaches and each coach has a number of seats but bus has a very few seats compared to a train so a train makes more profit than a bus.