The cyclist was escorted out of the tunnel by police, reports newspaper VG.
“We received reports of the cyclist as he approached the entrance to the tunnel and followed him with our cameras,” duty operator Stein Ekholdt at Oslo's central traffic coordinator (Veitrafikksentralen) told VG.
“He suddenly stopped and sat down, so we closed the tunnel,” Ekholdt said.
After the tunnel was closed at 20:33 on Wednesday, police carried out a minor rescue operation, with two police officers entering the tunnel from the Buskerud side by motorcycle and two from the Follo side by car, according to the report.
“The man did not seem to have much experience in cycling long distances, and especially not up hills. He had a three-kilometre long incline ahead of him. The bicycle was an off-road cycle,” Ekholdt said.
The coordinator said that the situation in the tunnel could have become dangerous.
“It was going well whilst he went downhill, but he started to struggle when he got to the bottom. He was up on the pavement and then down again. With strong backdrafts from large trucks, that can be dangerous, [the tunnel] is not designed for cyclists,” he said to VG.
Cars were forced to queue at the entrance to the tunnel while the rescue patrol retrieved the man. After police reached him, they found that he only spoke Turkish, but was able to show them that he was using Google Maps to navigate.
“We opened the tunnel again as soon as the man was in the police car,” Ekholt said.
The tunnel was closed for around 30 minutes in total.
Charges will not be pressed against the man, who was dropped off by police in Drøbak, Follo Police District operations leader Tore Nuven told VG.