The Heysen Tunnels are twin tube road tunnels which carry the South Eastern Freeway under Eagle On The Hill in the Mount Lofty Ranges in South Australia. The tunnels were excavated using a tunnelling machine normally used in heavy-duty mining operations which tunnelled through 500 metres of rock for each tunnel at an average rate of 3 metres per day. The tunnels were completed in 1998 and officially opened in May 2000. Each tunnel carries 3 lanes of traffic. On average, they carry a total of 45,700 vehicles per day. The maximum height of vehicles permitted in the tunnels is , the same as the Crafers and Mt Osmond interchanges. Laser height detectors monitor traffic to provide warnings to drivers before they attempt to enter the tunnel.