Don't get too cute as this is basically a rolling billboard, so think along the same line as a static billboard. You can only put so much information on one of those since drivers are the primary target audience, and the window for catching their attention is short. Do you have a catchphrase, a snappy name for your facility, a logo that has visual appeal, a website?

With four sides, you can push four different aspects of the business. For instance, one side is security - images of a camera, keypad, door alarm if you have those - and a phrase that speaks to the peace of mind security offers.

Maybe another side hits on the total access you're providing with the 24/7/365 approach, though you may be leaving money on the table by giving every tenant round-the-clock access. A lot of sites have a tiered pricing schedule based on the hours of access tenants get; may not be applicable to your facility, but it's out there.

I would probably NOT do a map; again, this is a rolling billboard and a map takes some time to work through. Not sure of the perceived value of being family-owned, either.

Upside is you have four sides and, as such, the opportunity to hit on four different aspects of your business. And with magnetic lettering and images, you can rotate the images. Just my two cents --