Introduction:
In this question, we are asked to identify which option is NOT a special means of transport. We are provided with four options: ambulance, autorickshaw, fire engine, and postal van. We need to determine which option does not belong to the category of special means of transport.

Explanation:
To answer this question, let's understand what special means of transport are. Special means of transport are vehicles that are specifically designed and equipped to perform certain tasks or provide emergency services. These vehicles are different from regular means of transport like cars, buses, and trains.

Ambulance:
- An ambulance is a special means of transport that is used to transport sick or injured people to hospitals.
- It is equipped with medical supplies and equipment to provide immediate medical care to patients during transportation.

Fire Engine:
- A fire engine, also known as a fire truck, is a special vehicle used by firefighters to extinguish fires.
- It carries firefighting equipment like hoses, water tanks, ladders, and other tools required to combat fires.

Postal Van:
- A postal van is a vehicle used by postal services for delivering mail and packages.
- While it may be a specialized vehicle for postal operations, it does not fall under the category of special means of transport as it does not serve emergency or specific tasks like ambulances and fire engines.

Autorickshaw:
- An autorickshaw, also known as a tuk-tuk or a three-wheeler, is a small motorized vehicle used for public transportation in many countries.
- It is not considered a special means of transport as it is primarily used for regular commuting and does not provide emergency or specialized services.

Conclusion:
Based on the above explanations, it can be concluded that the autorickshaw (option B) is not a special means of transport. It is a regular mode of transportation used for commuting purposes. The other options, namely ambulance, fire engine, and postal van, are all specialized vehicles used for emergency services or specific tasks.