Billboard Resolution?

Hi all,

Have the job of designing a large-ish billboard advertisement.

I’ve only ever done magazine-size ads before and was wondering if I could get some guidelines for designing this billboard ad in regard to resolution.

The billboard is about three metres (approx 10’) wide, so if I design it at 300dpi, it’s going to be an insanely large file and chew up a heap of RAM.

Tips?

After a bit of Googling I’ve come to some sort of a conclusion; do the ad at a fraction of the actual size (half size, for instance), with any photographs in the ad at that size, but have any text and graphics in the ad in vector format.

Thoughts?