West Gate Bridge safe: VicRoads THE strength of Melbourne's West Gate Bridge has been unaffected by cracks believed to have been caused by last week's heatwave, VicRoads says. The inbound lanes of the bridge reopened to traffic at 6am (AEDT) after road crews worked through the night to repair a large crack on the surface. VicRoads acting chief executive Peter Todd said the bridge surface has been repaired and the bridge is now safe. A second crack, 29 metres long, was also confirmed late on Monday by the road authority. Experts found two water-proof membranes immediately underneath the asphalt layer had separated, causing the two large cracks. "Neither in any way affected the structure or the strength of the bridge," Mr Todd said in a statement. VicRoads believes last week's record heatwave, where temperatures reached more than 41C for four days in a row, damaged the membranes, causing the steel section of the bridge to expand, then contract, when temperatures dropped. Mr Todd said the cracks were confined to one section of the bridge and more work will be done in coming weeks to replace that section of damaged membrane. The work will require the lanes to be closed over a weekend.