Start/stop is a system fitted to many vehicles with both manual and automatic transmissions.

It is designed to stop the engine when you are stationary, typically at a junction or in a traffic queue, to cut emissions.

The systems are specific to each manufacturer but all tend to have a common way of operating.

Each time the vehicle is stationary, and in the case of a manual car when it's not in gear, the system will stop the engine - although the car ignition will still be on and so will your lights heating, radio and so on.

When you go to move off, in a manual car by engaging the clutch to place the vehicle in gear or by taking your foot off the brake in an automatic, then the system will restart the engine.

However, start/stop systems will not trigger the engine to stop every time you are stationary. Each time you come to a stop the car's computer brain (ECU) will assess many different factors, such as the outside temperature, the engine's temperature, the battery state of charge, the time since the system last triggered and so on, before deciding to stop the engine or not.

Therefore you may find you stop but the system keeps the engine running.

Similarly when the system has stopped the engine, it will continue to monitor the battery usage from the car, with your lights, heating and radio all draining battery power, and it may restart the engine to ensure the battery charge condition is properly maintained - even though you may not be attempting to move off.

It may take some getting used to if you have not driven a car with one of these systems before and many cars have a button to disable the system.
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