G318 Ya'an section is already a mountainous area. Erlang Mountain Tunnel is the longest in the local area, with a total length of more than 8 kilometers. It is presumed that such a long tunnel journey is also a great test for driving novices. After the speed limit in the tunnel, a little depressed, and then there is no big pressure, only see LED lights on the top of the tunnel and two walls to play a variety of fantasy screen effects, a sense of boredom.