When stopped at traffic lights, if your vehicle has an automatic transmission, putting it into ‘Neutral’ will take the pressure off it until the traffic lights turn green, when you can put it back into ‘Drive’. When the automatic transmission is in ‘Drive’, it’s still driving the wheels even if you have your foot on the brake to keep the vehicle stationary at traffic lights, for example. If you were to take your foot off the brake, the vehicle would drive forward under power without you even pushing the accelerator since the engine is running at idle speed and is therefore driving the automatic transmission.
Considering how much time the vehicle spends at traffic lights at a standstill, it’s best for the automatic transmission to be in ‘Neutral’ while stationary. Automatic transmissions are highly complicated, sensitive pieces of machinery. Relieving the tension in it by putting it into ‘Neutral’ when you’re stationary and waiting around will go a long way to keeping it in the best possible condition and avoiding unnecessary wear and tear.
