New bus lanes on the Albertbridge Road in east Belfast have begun operating.
They are located between Castlereagh Street and the Newtownards Road and follow weeks of roadworks in the area.
Members of the public will face fines if they drive in the lanes on weekdays during peak traffic times - from 07:30 to 09:30 and between 15:30 to 18:30.
The changes form part of the Belfast Rapid Transit project, which is due to be introduced next year.
A spokesperson for Department for Infrastructure (DfI) said: "The new bus lanes will support a faster, more reliable bus service for people travelling along the Albertbridge Road.
They said they had already seen a "growing number of people switching to the bus on this key route".
Passenger numbers have increased by about 4.5% on Translink's Metro-4 bus route since other bus lanes were installed further along the route.
Some bus lanes were already in place along parts of the Albertbridge Road, but they have now been replaced and extended to cover two thirds of the carriageway.
The DfI spokesperson said the aim was to "encourage more people to use public transport, ultimately helping to reduce congestion on this busy arterial route into the city in advance of Belfast Rapid Transit coming into operation".
That forthcoming project will see "tram-like" vehicles operating along several main roads in and out of the city by September 2018.
The masterplan is designed to cut public transport journey times between the city centre and parts of east Belfast, west Belfast and the Titanic Quarter.
Several parts of the city have already witnessed traffic changes in preparation for the future system.
When the first bus lanes began to operate in September 2012, they led to long traffic delays and complaints from the public.
The department said the latest changes wee being introduced "during the summer while traffic levels are traditionally lower", in order to give motorists time to adjust.
"DfI would ask drivers to take extra care when travelling on this stretch of the Albertbridge Road until they are familiar with the new arrangements," its statement added.