Not all trains have air conditioning or heating, and there are several reasons for this:
Train types and routes: Different types of trains are designed for various purposes and routes. Some trains, especially those used for short commutes or in regions with mild climates, may not have air conditioning or heating systems because the temperature variations are not extreme enough to warrant their installation.
Cost considerations: Installing air conditioning and heating systems in trains can significantly increase the initial cost of manufacturing and purchasing the trains. In regions with limited funds or where climate control is not a high priority, train operators may opt for simpler and more cost-effective train models without these features.
Open-window design: Some trains, especially older models, may rely on open windows for ventilation instead of air conditioning. In certain climates, this might be sufficient to maintain a comfortable temperature inside the train.
Energy efficiency: While it might seem more cost-effective to have a central engine or generator for each train to power climate control systems in all carriages, it can actually be more energy-efficient to have decentralized systems. Providing each carriage with its own heating and cooling system allows passengers to control their environment individually. This way, only the occupied carriages need to use energy for heating or cooling, saving power when fewer passengers are present.
Environmental impact: Running a central engine or generator for each train would consume more fuel and produce more emissions, making the overall operation less environmentally friendly compared to decentralized systems. It's important for train operators to consider both passenger comfort and environmental impact when designing and operating their fleets.
Flexibility and maintenance: Having individual heating and cooling units in each carriage provides flexibility in configuring train compositions. It also allows for easier maintenance and repair since the failure of one unit does not affect the climate control in the entire train.
In conclusion, the decision to include air conditioning and heating in trains depends on various factors, such as climate, passenger comfort requirements, cost considerations, and environmental impact. While it might seem more cost-effective to have a central engine or generator for climate control, decentralized systems often offer better energy efficiency, passenger comfort, and maintenance benefits, especially in modern train designs.