The program aimed to cut down on the number of people drink-driving and "drink-walking" in the Southern Highlands on Friday and Saturday nights during the silly season.

The project was a combined initiative of the Southern Highlands Liquor Accord, Berrima Coaches and Wingecarribee Shire council and was funded by the RTA.

The first stage of its operation was hailed a success, with hundreds of passengers using the service each week.

The initial results far exceeded organisers' expectations and encouraged them to look at extending the service throughout the year, if funding was available.

Liquor accord president John Griggs said the organising committee, patrons and licensed premises in the Highlands were all very pleased about the three-week extension.

He said extra funding had also been secured to provide a second bus on and New Year's Eve, to focus on Moss Vale, Berrima and Sutton Forest.

Council's road safety officer Kim Davis said more than half of those using the bus were from Moss Vale, most were in the 18-25 years age bracket and there was an equal mix of men and women using the service.

She said there had been a reduction in the amount of alcohol-related crime in the Southern Highlands since the scheme was set up.

The program had also run successfully in Wollongong, Nowra and Kiama, but it had never been extended beyond January 3.

Mr Griggs said the additional funding would be accompanied by a push for patrons to pay a $2 donation towards the service.