Check out 'lasagne gardening' or 'no-dig gardening'. You can do this over a solid base such as asphalt or concrete. And the raised edges would definitely help to contain the thick base layer of cardboard or newspaper, then straw/hay plus compost that you plant into.

Also check out the Square Foot gardening method. The instructions there for the width to use could be useful. A 'comfortable for you' stretch to the middle without having to walk on the bed.

Probably the main ingredient is plenty of compost on hand to make a thick enough planting bed. It settles quite quickly and will need to be replenished before replanting.

Two pluses I am imagining are- you'll have safe and dry access to your garden; and, you could have a useful micro-climate with the warmth coming off the exposed asphalt that will extend your season for you.

Thanks;

I used lasagna gardening for my front garden last year, to think of all those back breaking years that my mother and I toiled to rip out the sod first!! The only thing that concerns me with using a driveway for a base as opposed to a lawn, is that I know many of my plants that had deep roots eventually dug down into the original lawn soil. I am curious to know how tall the raised bed will need to be to accomidate proper root growth!

I was thinking along the same lines with the benifits of my location, also I can set up a fence for things like cuc's and peas to grow along, outside of the garden and not have to use valuable garden space...