Freelanders and Passats that switch off when halted in traffic begin sale next year.

Stop-start technology, where vehicles turn themselves off whenever halted in traffic, is being adopted by two more makes – Volkswagen and Land Rover.

BMW already fits the system to its smaller-engined saloons with manual gearboxes and also the Mini. Citrn also has its own version, available on its C3 supermini and C2 city car.

Volkswagen is to introduce Stop-Start on its second-generation Bluemotion range of low-emissions, high fuel economy cars, beginning next year with the Passat. Land Rover, meanwhile, is to add the system to its Freelander line-up. In both cars, the system is similar. When the car is stopped, the gears in neutral and the clutch pedal raised, the engine stops. To restart, the driver simply dips the clutch. In each, there’ll also be an on/off switch on the dash.

For the Volkswagen, this and other refinements stretch fuel economy from the present model’s 55.4mpg best overall to 57.6 for the newcomer. CO2 output reduces from 136g/km to 128g/km.

It’s a similar story for the Land Rover. Compared to standard models with the TD4 turbodiesel engine, CO2 emissions reduce by 15g/km to 179, while fuel economy improves from 37.7mpg to 41.3. The system will be fitted as standard to Freelanders from mid-2009.

The engines in both vehicles are designed to re-start using a minimum of fuel. If you drive an older car, don't think you can achieve similar results by constantly turning off and on. Most actually use more fuel to restart than they would if left idling for up to three minutes.