The Homer Tunnel is the only road access to Milford Sound from the inland side (via the Milford Sound Highway). Without it, the journey would be impossible by vehicle. It's a single lane, meaning traffic can only pass in one direction at a time. This is managed by a traffic light system at each end. Be prepared for potential waiting times, especially during peak season. The tunnel itself is approximately 1.2 kilometers (0.75 miles) long and has a steep gradient descending towards Milford Sound.