Hi there! There are two kinds of emergency exit; Emergency Escape Staircase & Pedestrian Cross Passage Door
The Emergency Escape Staircase is located every 500 meters next to the extreme left lane, the exit leads to the street level.
Pedestrian Cross Passage Door is located every 100 meters next to the extreme right lane, the exit leads to the opposite bound tunnel.
To find out more about tunnel safety, you can read the full article here - https://bit.ly/2qodGsf