Traffic slowed to a standstill in Santa Venera on Monday evening as part of Regional Road was closed for the final stage of upgrading works.
Infrastructure Malta announced in a Facebook post earlier in the day that the northbound lane, from Santa Venera to Tal-Qroqq and Kappara, would be closed between 5pm and 5am from Monday to Saturday.
By 6pm, motorists were reporting hour-long traffic jams starting from the Santa Venera tunnels.
The closure is to allow overnight works on the final phase of the Regional Road Project, which involves the widening of the north-south link to six lanes - three in each direction - and the upgrading of seven of its junctions.
Authorities have said the lane that will be added within the northbound carriageway will provide safer access from the slip roads that join Triq il-Wied in Msida, Triq il-Ferrovija l-Antika in Birkirkara and Triq Kappillan Mifsud in Santa Venera with Regional road.
Meanwhile, works on the bridge structure over Triq il-Wied in Msida were completed in recent days.
The bridge built in the 1970s and which enables the two carriageways on Regional Road to pass over Triq il-Wied in Msida has been reconstructed to accommodate the new lanes and to improve the alignment of the road, making it safer and reducing the risks of accidents, the minister said.
The new bridge will be one of the widest structures of its type in Malta, with a total width of more than 23.5 metres.