I used to deliver pizzas for 5 years (most of this part time while going to school), so I know exactly what Greadius and mayakovsky are talking about.
Some places make the drivers use their own cars, and some places pay the driver more than others, but at all the places I worked at, you just get paid minimum wage + a certain amount for each deliver (or a $ amount for 'gas' money based on mileage you put on your car), and the rest of their income is entirely dependant on tips. The places that put a set amount on the $ they give me/delivery, it was usually $.50, unless it was X miles away, then it would be $1.
$1 or $0.26/mile doesn't really pay me enough to drive 7 miles with my own vehicle to get no tip (you also have to consider the time it takes to drive there and back to the pizza place). And people wonder why we set a limit on how far away we can deliver
Depending on where you work, the income can drastically vary. At one place I delivered to predominately college students, but at another place it was mostly upper to middle class income families.
Worst tippers: Some rich people, professional athletes, and drug dealers (we always know where the 'crack houses' are, at least 6 months before the cops raid the house).
Best tippers: Middle class income families, and college students at parties (especially at around bar time).
Average, I would say $1.50-$2.00 tips was average for me if you consider all the big tippers and all the 'cheapskates' or 'stiffs'. If you don't count the stiffers, then $2-$3 is about right.