Editing Sydney Harbour Bridge (section)

===Tidal flow===
The bridge is equipped for [[Reversible lane|tidal flow operation]], permitting the direction of traffic flow on the bridge to be altered to better suit the morning and evening peak hour traffic patterns.<ref>{{cite web |url=http://www.rms.nsw.gov.au/usingroads/managingtraffic/tmc_network.html |title=Managing the network|publisher=Roads & Maritime Services |date=6 September 2013 |access-date=9 June 2014 |archive-url=https://web.archive.org/web/20140610211513/http://www.rms.nsw.gov.au/usingroads/managingtraffic/tmc_network.html |archive-date=10 June 2014 |url-status=live  }}</ref>

The bridge has eight lanes, numbered one to eight from west to east. Lanes three, four and five are reversible. One and two always flow north. Six, seven, and eight always flow south. The default is four each way. For the morning peak hour, the lane changes on the bridge also require changes to the [[Warringah Freeway]], with its inner western reversible carriageway directing traffic to the bridge lane numbers three and four southbound. Until September 1982, during the evening peak the tidal flow was set as six northbound and two southbound lanes.<ref>Tidal Flow Operation on the Sydney Harbour Bridge ''Main Roads'' December 1983 page 109</ref>

The bridge has a series of overhead gantries which indicate the direction of flow for each traffic lane. A green arrow pointing down to a traffic lane means the lane is open. A flashing red "X" indicates the lane is closing, but is not yet in use for traffic travelling in the other direction. A static red "X" means the lane is in use for oncoming traffic. This arrangement was introduced in January 1986, replacing a slow operation where lane markers were manually moved to mark the centre median.<ref>Annual Report for year ended 30 June 1986] [[Department of Main Roads (New South Wales)|Department of Main Roads]]</ref>

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.{{citation needed|date = March 2014}}

When the Sydney Harbour Tunnel opened in August 1992, lane 7 became a [[bus lane]].<ref>Harbour Bridge Public Transport Lane ''[[Fleetline (periodical)|Fleetline]]'' issue 198 January 1992 page 13</ref><ref>Opening of Sydney Harbour Tunnel & Gore Hill Freeway ''[[Australian Bus Panorama]]'' issue 8/3 October 1992 page 38</ref>