Vehicular
Circulation
Advertising
exposure to Out-of-Home advertising is called Daily
Effective Circulation ( DEC ). DEC is computed by
using factors which calibrate period of exposure,
directional traffic and vehicle occupancy.
Non-illuminated
displays are allowed 12 hours of exposure, while
illuminated displays are allowed 18 or 24 hours
depending upon whether the lights are turned off at
midnight or daybreak.
All two-way
traffic is converted to effective directional traffic
and DEC further converts traffic counts to people
exposure. The current load factor used for adult 18+
vehicle occupancy is 1.35.
Traffic
counts are derived from two sources: official and
manual.
Official
counts are generally available from departments of
transportation at city, county or state agencies.
State counts are taken on most roadways in three-year
cycles, while city and other regional agencies provide
new data less frequently. Factors used for converting
official 24 hour traffic counts to DECs are shown
below.
Manual counts
are performed by the plant operator. The tally method
utilizing hand tally counters is recommended. Short
counts of vehicles, 15 minutes in duration, are
conducted between 9.00 am and Noon or 1.00 and 4.00
pm.
At the right
are two sets of factors used for converting the manual
counts to one hours equivalents- the factors vary by
time of count. The second set of factors, which vary
by period of exposure, expand the one-hour equivalent
to DEC.
Factors
Used to Convert Official 24-Hour Counts to DEC
Important:
if any count, manual or official, is taken on one way
street, the factor must be doubled because of the
built-in divisor for directional circulation. However
never double the 15 minute multiplying factors nor the
base count of the vehicles.
1.35 = Adult 18+ Load Factor
95% = The percentage of the total daily traffic that
passes in an 18-hour period.
66.6% = The percentage of the total daily traffic that
passes in a 12-hour period.
