Motorists stopping in lanes or reversing to avoid copping tolls by entering Sydney's new M4 East tunnels have prompted transport officials to urge drivers to slow down and continue on if they mistakenly end up heading onto the new roadway.

Several drivers of trucks carrying dangerous goods have also reversed or stopped just short of entering the new three-lane eastbound tunnel at Homebush over the past two days. Dangerous goods trucks are prohibited from Sydney's motorway tunnels because of the risks they pose.

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While traffic flows on the M4 East and connecting roads were smooth during the morning peak on Monday, transport authorities say the first test will come next Tuesday, when all of the city's schools have reopened after the holidays.

Traffic volumes on roads across Sydney, including the new M4 East, remain light due to the school holidays. The M4 East, which is the first major stage of the $16.8 billion WestConnex toll road, was opened to motorists in the early hours of Saturday morning, after more than three years of construction.