CityLink is yet to find the cause of a computer glitch that has forced the closure of two of Melbourne's main road tunnels, bringing morning peak hour traffic to a standstill.
The city's Burnley and Domain tunnels remain closed on Wednesday after CityLink's neon speed and lane-changing signs stopped working about 5am (AEST), a VicRoads spokesman said.
And CityLink infrastructure manager Warren Gourley said he could not guarantee the tunnels will be open in time for evening peak hour.
'I would certainly hope so. At this stage it's still (too) early to call,' he told Fairfax radio on Wednesday.
'Our team is very much focused of finding the root cause and getting our system back online.'
The IT problem affected the tunnel's incident detection and safety systems that are activated in the case of an accident, Mr Gourley said.
The network problem also affected the back-up system.
The tunnels connect Southbank, Melbourne's CBD and Richmond under the Yarra River, with the closure causing gridlock on Melbourne's roads.
Traffic is heavy inbound on the Monash and West Gate freeways and all roads around the Melbourne CBD.
The tunnel closures even backed up traffic on the city's other roads, which then delayed some tram routes by up to an hour.
'The worst-affected routes are those which cross Punt Road and Hoddle Street,' Yarra Trams said in a statement.
It remains unknown, however, if motorists could get a refund from the CityLink delays.
'Our policy is that people who were caught up in the initial closure of the tunnel, they should call the call centre,' Mr Gourley said.
'We rely on getting the message out to people so they're informed on the potential of delays.'
Drivers of heavy vehicles travelling from Melbourne's east are advised to leave the Monash Freeway at Warrigal Road.
Motorists travelling from the west are advised to use Kings Way.