It was planned as a two-tube tunnel, (one two lane tube for each direction), but lower than expected levels of traffic have meant that it has remained a single tube, single lane, two way tunnel. At its opening it was one of the best equipped tunnels with safety and surveillance systems: emergency phones, fire detectors, video surveillance, traffic signalling, radio and phone connections, air circulation monitoring and carbon monoxide sensors.
Less than a month after its opening, in late June of 1991, the Slovene terminus of the tunnel and its border post were briefly seized by an armored detachment of the Yugoslav People's Army during the Ten-Day War. The site witnessed brief but intense fighting, which included the ferrying of reinforcements to the Yugoslav troops by helicopter and culminated in an ineffectual airstrike by the Yugoslav air force. The border checkpoint building was heavily damaged in the crossfire.