Kelly Burke, The Sydney Morning Herald

WHEN it comes to Sydney traffic, time really is money, according to a study that shows drivers who use toll roads are making huge savings on fuel and time spent in the car.

The six-day peak-hour survey by the NRMA shows that motorists prepared to pay the tolls are getting to work and back home again on average 75 per cent more quickly than those who take the free alternative routes. They are also using up to 40 per cent less fuel.

The difference between motorways and their free routes is even more marked on Saturday, the survey found, with drivers on toll-free routes taking more than twice as long as those on motorways, and using 45 per cent more fuel.

Drivers living in the outer north-west and paying four tolls to get to the city - on the M7, M2, the Lane Cove Tunnel and the Harbour Bridge - are reaping a 94 per cent saving in travel time, taking an average of 47 minutes.

That saving comes at a cost: further analysis by the Herald, based on Saturday's average petrol price of $1.18 a litre, shows those drivers spend near-identical amounts on tolls and fuel. A driver using the M7 entry point at Sunnyholt Road in Quakers Hill would have spent $11.61 on the four tolls, and $11.62 on petrol - a total cost of $23.23 for the 40-kilometre trip.

That appears less of a burden when the time and fuel costs of avoiding tolls are added up: the alternative toll-free trip takes 91 minutes, and the fuel cost leaps to $15.46. In effect a driver using the tolls is paying $7.77 to save those 44 minutes.

The NRMA's motoring and services president, Alan Evans, said the survey, conducted with identical cars in morning and afternoon peak times, showed that the north-west and M4 routes offered the best value for money. Using the M5 saved less time.

Nevertheless, motorists in the south-west are paying $4.13 more in fuel to avoid the $3.80 toll, and taking almost twice as long to reach the city as drivers using the M5. People from Penrith using the M4 are paying an additional 92 cents after taking tolls and fuel costs into account, yet reaching the city 42 minutes faster.

Mr Evans said the argument for completing Sydney's missing motorway links had never been stronger, not only to solve chronic traffic problems, but also to help the environment by reducing fuel consumption.

More needed to be done to find a solution for the northern beaches and the Victoria Road bottlenecks, he said.

The study found that trips from Brookvale to Cammeray via Pittwater Road took 44 minutes and the toll-free route from Parramatta to the city via Victoria Road took 50 minutes.