There are two crossings of the Thames at Dartford. A tunnel and a bridge. Travelling north you go through the tunnel. South you cross the bridge. They are both toll crossings.
Looking downriver from bridge
The exit point seems huge
It gets big fast
Its not a long tunnel, soon see the exit
Entering the tunnel from the south
It looks bad but the traffic is just slow moving for a bit, this side goes through 2 tunnels of 2 lanes each.
The traffic going towards the camera will go through the tunnels under the Thames