PUZZLE 048 Tunnel Vision

We need to use this truck to get through to the other side of the tunnel, but the truck is just a little bit too tall and it can't get through.
It looks like it would get through if a little something was removed from it, but what?
You're not allowed to break the truck or take off anything that isn't normally removeable.

Hint 1

You're not allowed to do anything to alter the tunnel such as enlarging the hole.
You need to solve this by working only on the truck.

Hint 2

The roof of the truck can't be removed and the truck must not be damaged.
It's not only parts of the truck you should be considering removing here.

Hint 3

Instead of worrying about the top of the truck getting hit, you should be focusing on the bottom of the truck.

Super Hint

Let's think about the tyres.
Is there anything you could remove that might help?
Bear in mind that the truck is only a tiny bit too tall to fit through the tunnel.

Answer for 'Tunnel Vision'

The answer is 'AIR'.