Western Sydney 'burdened' by M8 motorway delays after sprinkler bungle

Three Sydney mayors have called for better infrastructure in the city's southwest after motorists experienced extensive delays and traffic on the M8 Motorway this morning.

Several lanes were forced to close after a fire sprinkler test flooded the tunnel, forcing traffic to a halt on both the M8 and M5 in southwest Sydney.

One lane in the tunnel between St Peters and Beverly Hills reopened in both directions at about 7.50am after being closed earlier due to late running maintenance overnight.

Traffic was backed up for 27km and continues to be slow-moving through the tunnel.

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Liverpool Mayor Ned Mannoun, Fairfield Mayor Frank Carbone and Campbelltown Mayor George Greiss have urged the state government to "reevaluate" its infrastructure in southwest Sydney, as the area's population continues to grow at a quick rate.

"Our community in South Western Sydney is unfairly burdened by both the traffic chaos caused by the M8 tunnel incident and the broader infrastructure deficit," Mannoun said.

"We are the engine of Sydney's growth, and it's high time our residents receive the support they deserve."

Carbone said that Fairfield residents play "a vital role in the economy," and said motorists are paying "premium tolls for a car park," which further pressures families in the cost of living crisis.

Greiss called for toll refunds to be issued to motorists stuck in traffic this morning.

"Campbelltown and South Western Sydney, in general, are absorbing a significant portion of Sydney's population growth," he said.

"Despite this, we continually face infrastructure challenges.

"The toll refund is a step towards acknowledging the strain on our residents and demanding the necessary resources for sustainable growth."

At 2pm AEDT all lanes of the M8 reopened with a reduced speed limit of 60 km/h.