How is it that you come up with the DEC number?
Calculating the Daily Effective Circulation (DEC) is relatively easy. You take the traffic that goes by the billboard based on your 24 hour traffic count (which is a two way count normally) and divide by 1/2. Then take this number and multiply by 2 due to an average of 2 people per car [or you can just use the 24 hour two-way count since 1/2 x 2 = 1]. Then you have to determine how long the billboard is illuminated for. If it is non-illuminated, take your 24 hour count and multiply by 12. If it is illuminated until midnight, then multiply by 18. If it is illuminated all night, then it equals your 24 hour count. That’s all there is to it.
Is it an accurate measure? Obviously, it’s pretty ballpark – so I would not get too uptight over being 100% accurate. It’s a very basic measure of traffic past a sign.
Thank You for the direction in calculating the DEC!
I also found a site that was a little more in depth with calculating.
Thanks for sharing that extra resource. Traffic Audit Bureau (TAB) have been around for a long time and are great people.