A collision involving two vehicles brought northbound traffic in the Sydney Harbour Tunnel to a complete halt on Saturday afternoon. The incident occurred within the tunnel itself, causing significant disruption for commuters. Authorities have closed the northbound lanes to manage the situation and assess the damage. Details regarding injuries, if any, have not yet been released. Motorists are advised to avoid the area and seek alternative routes. The closure is expected to last for an extended period, impacting travel times across the city. Transport officials are working to clear the scene and reopen the tunnel as quickly as possible.