When many people think of future transportation advancements, self-driving cars immediately come to mind. Although those vehicles will almost certainly become prominent as technology improved, there are other cool car-related concepts in the works that are fascinating in their own right.

Take a look at these four:

1. Hybrid Air Technology

Most individuals have at least a basic understanding of how hybrid cars work. In addition to engines powered by gas, they have components that allow drivers to partially or completely operate the vehicles with electricity. This option significantly cuts down on fuel consumption, making stops at gas pumps less necessary.

However, recent research indicates hybrid cars currently on the market may not be as good for the environment as people think. That's because of the process used to create the cars' batteries.

A report shows the battery production process creates 150-200kg of carbon dioxide equivalent per kilowatt-hour. Plus, only five percent of lithium batteries get recycled versus 90 percent of conventional batteries.

However, as the name suggests, hybrid air technology works with compressed air and does not require a lithium-ion battery or electricity. The new engineering — in development by Peugeot — offers three driving modes and automatically adjusts to the best one depending on driving conditions.

Manufacturer statistics indicate the technology could reduce fuel consumption by 45 percent during city drives.

Outside the automotive sector, many other industries rely on compressed air. Often, it's because companies need on-demand access to clean, dry air, particularly when producing items in factories.

2. The AIRPod Vehicle

The concept above still requires using gas to propel the car in certain situations. However, the AIRPod is even more revolutionary because it entirely runs on compressed air and does not cause pollution.

The latter characteristic is possible because no combustion occurs. Instead, cold air compressed to 300 times the atmospheric pressure gets heated and fed into a piston engine's cylinders.

Also, there's a filter on the tailpipe. It makes the air that comes out of the car cleaner than that going into it. Drivers can recharge their cars at home with an air compressor or at filling stations for as little as $3.

The AIRPod's creators won a development deal for the vehicle on the TV show "Shark Tank" and want to manufacture the tiny car regionally in micro plants. They believe that arrangement will reduce potential logistical issues.

3. Augmented Reality Displays

Automakers perpetually look for ways to improve driver safety, and one of the ways they're doing that is by developing head-up displays enhanced by augmented reality.

Researchers know there are things artificial intelligence (AI) can do better than humans. In the case of augmented reality, special displays could help drivers keep their eyes on the road while also receiving information to keep them more informed during trips.

The displays can give details about what's happening around a vehicle or remind drivers of speed limits. They use holographic outputs and are extremely realistic, helping people behind the wheel feel more confident during their trips.

4. Pneumatic Regenerative Brakes

Many hybrid and electric cars have regenerative braking systems that use energy produced by a vehicle's turning wheels to recharge the battery with kinetic energy.

However, researchers are looking at a way to engineer a regenerative braking system that depends on pneumatics. If installed alongside a traditional braking system, it could minimize the overall energy requirements needed for the car's operation.

On the other hand, researchers say such a pneumatic system would not be appropriate for smaller vehicles or those that travel long distances. In the latter case, drivers don't apply the brakes frequently enough for the regenerative effect to be noticeable. Instead, they propose using it on a city bus.

The system contains a double-action piston compressor, a pressure vessel and a clutch linking the vehicle's transmission axis to the compressor. Scientists involved in testing the pneumatic braking system proposed above say it ultimately reduced energy consumption by 2.45 percent. They also say the power stored up with the regenerative system is useful for propelling a vehicle's components, such as windshield wipers.

These examples illustrate why there's so much to get excited about in the automotive sector. If these technologies make it to the mainstream, they could change how the vehicles of tomorrow function.