Should Automatic Transmission Cars Shift to Neutral at Red Lights?
2 Answers
Automatic transmission cars can shift to neutral when waiting at red lights for more than 30 seconds. For waits under 30 seconds, simply applying the brake is sufficient. Using N gear while stopped at red lights reduces engine load, and since red light waits can sometimes be lengthy, keeping the brake pedal depressed for extended periods can be tiring. When waiting at red lights in D gear with the foot brake applied, because the passive wheel in the engine and transmission's torque converter is fixed, this creates a reaction force applied to the driving wheel, increasing the engine load. This can be understood as hindering engine operation. Consequently, the engine ECU increases fuel injection, leading to higher fuel consumption, which is why you can observe very high instantaneous fuel consumption when braking to a stop. It is not recommended to use P gear while waiting at red lights because shifting from P to D gear can easily cause the car to reverse, affecting the vehicles behind and potentially leading to rear-end collisions in severe cases, for which you would also bear some responsibility. Currently, some vehicles are equipped with an "autohold" function, which is an automatic handbrake. After pressing the button to activate this function, the vehicle automatically brakes once stopped, without the need to shift from reverse to drive gear, maintaining the parking state. However, not shifting into neutral still poses certain safety risks, such as the vehicle rapidly starting if the accelerator is accidentally pressed, which can easily lead to collision accidents. Additionally, the auto start-stop function is also suitable for use at red lights, saving fuel to some extent, and the engine, when turned off, does not emit exhaust gases into the car interior.
I've been driving automatic transmission cars for over twenty years and found that it's generally unnecessary to shift into neutral when stopping at traffic lights. If the light is short, just stay in D gear and hold the brake firmly, so you can start immediately with quicker response. Only when the light is exceptionally long, say over half a minute, do I shift to N gear and also engage the handbrake to give my right foot a little rest, which might save a tiny bit of fuel, but honestly, the effect is minimal. The key is to prevent the car from rolling—safety always comes first. Handle it flexibly based on the actual situation. Don’t make shifting a habit, as it might increase transmission wear unnecessarily, which isn’t worth it.
