From what it looks like:
- Vehicles coming in around motorcycle size, about 1 Hull and 1 Structure.
- Vehicles coming around car size, about 2 Hull and 2 Structure. Enclosed car-sized vehicles such as ground cars gain +1 Hull.
- Military vehicles have 5 Hull and 5 Structure, and heavy vehicles such as GCarriers get 8 Hull and 8 Structure, possibly higher for MBTs (10 Hull / Structure?)
Between civilian car-sized transportation and military transports, one might expect large transports such as buses, trucks and articulated trucks.
- Van: 3 Hull, 3 Structure.
- Civilian bus: 4 Hul, 4 Structure.
- Civilian excavator (JCB): 4 Hull, 4 Structure.
- Truck: 5 Hull, 5 Structure.
- Heavy Truck: 6 Hull, 6 Structure.
That's roughly my guess, based on what I read in the table on p. 103. Scouts has more vehicles, and I'll refine my model based on what I read there, once I get my copy.