lane markers were manually moved to mark the centre median. It is possible to see odd arrangements of flow during night periods when maintenance occurs, which may involve completely closing some lanes. Normally this is done between midnight and dawn, because of the enormous traffic demands placed on the bridge outside these hours. When the Sydney Harbour Tunnel opened in August 1992, lane 7 became a bus lane. Tolls The vehicular traffic lanes on the bridge are operated as a toll road. Since January 2009, there is a variable tolling system for all vehicles headed into the CBD (southbound). The toll paid is dependent on the time of day in which the vehicle passes through the toll plaza. The toll varies from a minimum value of $2.50 to a maximum value of $4. There is no toll for northbound traffic (though taxis travelling north may charge passengers the toll in anticipation of the toll the taxi must pay on the return journey). In 2017, the Bradfield Highway northern toll plaza infrastructure was removed and replaced with new overhead gantries to service all southbound traffic. Following on from this upgrade, in 2018 all southern toll plaza infrastructure was also removed. Only the Cahill Expressway toll plaza infrastructure remains. The toll was originally placed on travel across the bridge, in both directions, to recoup the cost of its construction. This was paid off in 1988, but the toll has been kept (indeed increased) to recoup the costs of the Sydney Harbour Tunnel. After the decision to build the Sydney Harbour Tunnel was made in the early 1980s, the toll was increased (from 20 cents to $1, then to $1.50 in March 1989, and finally to $2 by the time the tunnel opened) to pay for its construction. The tunnel also had an initial toll of $2 southbound. After the increase to $1, a concrete barrier on the bridge separating the Bradfield Highway from the Cahill Expressway was increased in height, because of the large numbers of drivers crossing it illegally from lane 6 to 7, to avoid the toll. The toll for all southbound vehicles was increased to $3 in March 2004. Originally it cost a car or motorcycle six pence to cross, a horse and rider being three pence. Use of the bridge by bicycle riders (provided that they use the cycleway) and by pedestrians is free. Later governments capped the