Bus timetables and routes were rewritten to allow for construction to begin of the light rail line from Circular Quay to Randwick. Market Street will be a challenge once part of George Street is closed to vehicles on Friday. Credit:Sahlan Hayes CBD transport co-ordinator general Marg Prendergast said the closure of the first part of George Street on Friday would put significant pressure on surrounding streets such as Market, King, Elizabeth, York, Castlereagh and Clarence. "What we are worried about is Market Street – particularly Market and Clarence - because the Hills buses have to get back out," she said. "[The change to the bus network] was only an enabler for the main game, which is the closure of George Street. It has the potential to bring us gridlock. Our mission is to avoid that happening."

A lane of the closed section of George Street between Market and King streets will be maintained for emergency service vehicles and for business owners to access three driveways. Access to the lane on George Street will be controlled. George Street provides about 25 per cent of north-south traffic capacity in Sydney's CBD, and Ms Prendergast said the closure of the first section was "just the tip of the iceberg". Extra police will be stationed at key intersections to ensure commuters follow the rules. The entire route for the light rail line is 12 kilometres long, and its construction has been divided into 31 zones, each of which will be closed separately. By late next year, 17 zones will be off limits to all vehicles. A zone between Hunter and Bathurst streets will never be reopened to traffic. The second section of George Street – between Market and Park streets – will be closed for construction work from December 3.

Motorists are urged to avoid the city if they can and, if they need to enter the so-called inner core of the CBD, to avoid the peak travel periods. "York Street in the morning also has to be avoided. That's why it's in drivers' best interest to just skirt the city, and particularly avoid the peak," Ms Prendergast said. "If you're going to come in the middle of the day, you're going to have to find an underground car park if you drive." Those driving into the CBD from the north are advised to use the Western Distributor or Cahill Expressway. Roadway capacity on Macquarie, College and Wentworth streets has been increased as part of efforts to create a key north-south corridor, and an alternative to George Street. Martin Currie transport analyst Andrew Chambers said the reduction of road capacity in the CBD from the closure of George Street would undoubtedly put pressure on other roads.

However, he doubted it would funnel a large amount of extra traffic into the Cross City Tunnel, which is operated by Australian toll-road giant Transurban. "If congestion gets worse, those people who didn't want to use a toll road will be more incentivised to use that tunnel ... but I imagine it would be quite low," he said. Unlike the patchwork of roads above ground, the tunnel gave motorists only a few ways of getting to their destinations in the city. Mr Chambers said more congestion in the CBD could discourage motorists, which could affect patronage of other toll roads in the city. "The Eastern Distributor is the classic example. If you can't get off it, because of congestion [in the CBD], you might get less traffic."