They sell grates that are rated for weight. I know Home Depot has the plastic ones, but I'm not sure if they will support 2 tons (you'll have to look and see). Steel grates are available, but are a more expensive option. Basically you'll want to remove the existing concrete using a concret saw, then backfill with new concrete using a form to create a channel for the water. A 4x4 built of plywood (so it's easy to pull out of the set-up concrete) works well. Pitch the bottom of the form so that the water drains off to the correct side - drop it 1/4" per 3 feet and the water will drain properly.

Another option:

Use a concrete saw to remove a 8 inch wide trench about a foot from where the door hits your concrete pad. Dig the trench to the side deep enough that the pitch of the bottom of the trench falls off to that side. Lay in a piece of drain tile on the bottom, holes down and socked. Back fill with gravel. If the top of the drain tile is at least a 6 inches below the surface, your tires won't crush the pipe (the weight gets distributed by the gravel and edges of the trench). This is probably the cheapest and least time consuming method, but it won't be as pretty as the one above.

Either of the above is doable by the average joe with some power hand tool experience. You can rent the saw at Home Depot.

-- John