The NSW government is considering lowering the cost of train fares to Sydney Airport and raising tolls for cars in a bid to alleviate traffic gridlock.

A Productivity Commission report has recommended that the price of the $15 train ticket from the city be dropped significantly, following a huge surge in usage after the NSW government dropped prices to two nearby stations, Green Square and Mascot.

After the ticket price to those stations was dropped by 45%, usage increased by 50%.

Currently, only 11 per cent of the Airport Train's seats are filled by commuters, who have long complained that the $15 fee from the city to the airport is too close to the cost of a cab fare, and is uneconomical if several passengers are sharing a cab.

The rub is in the fact that Cityrail actually only charges $3.20 per passenger, while the rest of the ticket price -- a further $11.80 -- is charged by the private operator of the airport train station, Airport Link.

Surprisingly, it's Airport Link which is showing some willingness to budge on its high prices for once. After 10 years of poor patronage, Chief Executive Tim Anderson told News Limited, "The Productivity Commission has made comment on the structure and if the state government wishes to review the arrangements we'd be prepared to participate in the discussion."

It's expected that if Airport Link did drop prices, the NSW government would give it some compensation in the form of a "shadow fare" for each passenger that takes the train to the airport.

However, it would also take cars off Sydney's heavily congested M5 freeway, which the NSW government is considering tolling more heavily as a disincentive to driving to the airport.

Greater train use would also reduce parking pressure on Sydney Airport, which has just had to start construction on yet more parking -- another 2,000 spaces.

Sydney airport was recently slammed for having among the world's highest airport parking charges.