Gridlock greeted the opening of the Queensferry Crossing, with close to 100,000 vehicles thought to have used the bridge on its first day.
Drivers are warned to expect further congestion this weekend when 50,000 people take part in walks across the new crossing.
Tailbacks from the bridge on the M90 yesterday stretched for at least five miles north into Fife, and three miles south as far as the M9.
Traffic Scotland, the official information service, said the surge of extra traffic had doubled some journey times.
The total number of vehicles carried by the crossing, measured by electronic sensors, is expected to be far more than the 80,000 a day that cross the Forth Road Bridge, which it will replace.
First over the 1.7-mile bridge when the northbound carriageway opened at 1:49am was economy secretary Keith Brown and Roy Brannen, chief executive of the Scottish Government’s Transport Scotland agency, which is in charge of the £1.35 billion project.
They travelled in a support vehicle from the Forth Crossing Bridge Constructors consortium which built the bridge, followed by a police car. The southbound carriageway opened an hour later at 2:49am.
Mr Brown said: “The weather this morning proved a perfect backdrop for all those who wanted to be a part of this historic day.
“This is leading to large volumes of traffic on the approaches which is causing some delays.
“People are very excited about this opportunity and we appreciate the patience that they are showing when waiting to cross.
“You immediately notice coming over the new bridge the absence of the ‘slap, slap, slap’ that you get on the existing bridge. It’s a very smooth passage.”
However, motorists were soon venting their frustration at the delays.
Seonaidh tweeted: “First time I’ve seen North bound queues at 8am. Great bridge but utter traffic chaos.”
Emma tweeted: “Don’t understand why the old bridge can’t open for those who just want to get home! #QueensferryCrossing #shambles.”
Transport Scotland said the delays were mainly on the approach roads and traffic on the bridge was free flowing.
The crossing has a temporary 40mph speed limit which will be raised to 70mph when it becomes a motorway.
That will be around mid-October once new road links are completed to the Forth Road Bridge for buses.
A spokesman said: “Peak traffic began earlier than usual from around 6am and has continued across the day.
“Drivers are coming over the bridge and coming back again, which triples normal traffic.
“Observations of day trippers, people crossing the bridges twice, and drivers taking the opportunity to become familiar with the new roads layouts, have contributed to the congestion.
“However, it’s understandable because there is only one opportunity to cross the bridge on its first day.”
The only reported incident was a southbound lorry breaking down on the bridge around 7am, which was moved onto the hard shoulder.
Traffic Scotland operator manager Stein Connelly told The Scotsman: “Things went exactly as we thought they would – we have had an early arrival of people wanting to experience the drive across the Queensferry Crossing.”
Mr Connelly said if the lorry had broken down on the Forth Road Bridge, traffic would have been reduced to one lane, causing more disruption.
The new bridge remains open today but is then due to close early on Friday for six days until next Thursday for the bridge walks, and the official opening by the Queen on Monday.
All traffic will be switched back to the Forth Road Bridge, which is open today for cyclists and pedestrians only on a segregated footway on the east side of the bridge.
Neil Greig, of the IAM RoadSmart motoring group, said: “The first day or two was always going to be difficult as drivers get used to the new layouts and the temporary speed limits. The real test will come next week when the novelty wears off and real life takes over.”
Further walks are being laid on for 10,000 local residents and school pupils next Tuesday. A clear-up operation the following day will prepare for the Queensferry Crossing to open permanently, which is likely to be in the early hours of next Thursday.
The Forth Road Bridge’s west footway will be open to pedestrians only on Saturday and Sunday, with cyclists using the east footway.
The bridge will be closed to both pedestrians and cyclists on Monday for the Queen’s visit. The east footway re-opens for use by both from Tuesday.