Can certain vehicles be started by keeping the gears engaged?

It is generally unsafe and not recommended to start a vehicle with the gears engaged. Most modern vehicles are equipped with a safety feature called a "neutral safety switch" which prevents the vehicle from starting unless the gearshift is in the neutral position. This is done to prevent the vehicle from lurching forward or backward unexpectedly. Some older vehicles, tractors, or specialized vehicles may not have a neutral safety switch and may allow you to start the engine with the gears engaged. However, this is not a safe practice and can lead to accidents or damage to the vehicle.