So here's a shot with a Toyota in the bed...or is that a Nissan...? whatever...they're all the same.
Looks like 4 lanes wide to me.

The really interesting thing to me though is, that while there is a difference in size between the Terex and the CAT 797, the most poignant difference is the method in which they motivate.
Both companies relied on their core competence to develop these huge earth/mineral moving machines.
Terex being owned by GM at the time relied on their railroad experience, while Cat being Cat relied on their typical direct drive experience.
At the time, GM owned Terex, they also owned EMD, Electro Motive Diesel which produced trains. Their approach was to power the Terex using the diesel engine/electrical generator/traction motor method...ie...a train on rubber tires.
CAT however, relied on their direct drive capabilities, which married fuel fired power plants with torque converters and automatic transmissions. I can't help but believe the later is a more efficient method to use for rubber tired vehicles.
Thus the reason Terex produced a single vehicle while CAT continues to produce multiple 797 dump trucks.