Add me to the "who cares" group.
Anyhow, when bobtail my Volvo is pretty slow in the lower gears since the drive axle is geared for the highway, but once it hits 40 MPH it has some serious get up and go.
It all depends on the drive axle gearing. Get a tractor built for city delivery service and it will have more than adequate acceleration but it will get lousy milage on the highway and be spinning pretty good RPM.
A real world example. As I said, once it is up over 40 my Volvo has plenty of punch. Towing a 19k fiver with a smart car on the deck I cruise at about 62 MPH - 1450 RPM. If I come up on a slower moving semi, and want to get around fast to avoid holding up traffic, I can punch it and we will be at 75 by the time my cab comes even with his.