raised bed questions

raised bed questions

I have an area of my driveway that I'd like to use for gardening. However, right now it's hard-packed gravel. Weeds do pretty darn good at growing there, and it drains, so it's not like it's cement. I want to put some raised beds there, about a food deep. What I'm trying to figure out is, do I need to get the gravel taken up and replaced with topsoil (something I've already gotten an estimate for and it's not too bad), or will my veggies do fine if I just put the raised beds right on top of the gravel?
What I did last night

What I did last night

ANOTHER unknown

ANOTHER unknown

What a night!

What a night!

Yay finally!

Yay finally!

Lenten Rose (Hellebore)

Lenten Rose (Hellebore)

Oh noes! Garden pests!

Oh noes! Garden pests!