''There's a view that we have got to close city streets off to cars. But there are so many taxis and buses even without cars,'' professor Hensher said. ''We're at a crunch point in terms of capacity and we might need to talk about building an underground bus depot.'' Fixing peak-hour traffic chaos on York Street has perplexed the state government and the City of Sydney since the late 1980s - a similar idea was floated by the then transport minister, Bruce Baird, in 1989, when he suggested unused tram tunnels under the city could become a bus terminal. But commuters still travel at a snail's pace. Every weekday between 7am and 9am, an average of 550 buses travel down the strip, and 300 make the trip during 4pm and 7pm, according to figures provided by the Department of Transport. Congestion can become so bad, buses and taxis are often backed up across the Harbour Bridge to the northern approaches, prompting some southbound drivers to use general traffic lanes and then drive back into the bus lane at the top of York Street. Adding to the frustration is that journeys from the northern beaches and the north shore are often shorter than the trip across the bridge into the main stops at Lang Park and Wynyard.

The Rail, Tram and Bus Union said bus drivers were verbally assaulted at least once a week because of bad traffic. ''We do get a lot of frustrated passengers. When there are long delays [along York Street] it makes drivers' jobs very difficult,'' Gary Way, the NSW president of the union's tram and bus division, said. ''Then this makes the drivers late for their next trip.'' Mr Way said, if the state government could eliminate congestion along York Street, it would ''help drivers no end''. Proposed fixes to congestion over the years have included moving bus lanes and stops to the middle of the road, and banning cars. But the most oft-quoted solution has been light rail. Dr Michelle Zeibots, from the University of Technology, Sydney's, Institute for Sustainable Futures, said light rail just makes sense. ''The demand for public transport services that terminate at York Street has grown so much that buses just can't pick up and put down the crowds of passengers quickly enough. Consequently, they jam up the street,'' Dr Zeibots said.

''This doesn't mean there's anything wrong with buses. It's just that they aren't designed to cope with really big numbers of people like light and heavy rail, which has more doors to each carriage so that vehicle loading times are faster.'' A spokesman for the Department of Transport said new traffic signals at Carrington Street and Margaret Street, extra clearways and bus lanes, and a reorganisation of bus stops were all measures that had already been put in place to alleviate congestion. He signalled that the department was also looking at options like changing traffic lights, bus lanes and bus layover spots. The Minister for Transport, Gladys Berejiklian, said the government was taking congestion seriously and blamed a lot of the problems on the previous government. Loading

"The previous Labor government's failure to build the North-West Rail Link, and their slashing of ferry services has contributed in no small way to the current congestion problems in York Street and the CBD,'' Ms Berejiklian said. A spokeswoman for Sydney Lord Mayor Clover Moore said York Street could not be looked at in isolation, but the government had a responsibility to improve movement around the city. ''The City of Sydney eagerly awaits the State Government's promised City Centre Access Plan which will outline plans for future bus network routes and bringing light rail into the city centre.''