The Effects of Commercial Electronic Variable Message Signs ...

APPENDIX B—DETAILED DESCRIPTION OF STUDIES
B.1 ON-ROAD INSTRUMENTED VEHICLE APPROACH
The most effective research strategy to emerge from the analysis undertaken in section 6.0 is the
on-road instrumented vehicle method. The following describes one possible study which might
be conducted using this method.
B.1.1 Method
The on-road instrumented vehicle method employs an instrumented vehicle which is brought to
the study site, along with a crew of about two or three researchers. The study site is a location
where there is at least one CEVMS installation along a public access roadway. Preferably, there
would be several CEVMS installations at the location so that a single test driving scenario might
pass a few different CEVMS in the course of about half an hour of driving. The investigation
should include at least two or three study sites which already have CEVMS in place. At each
study site, approximately 20 to 30 research participants would be recruited from the local area.
Each research participant would drive the instrumented vehicle along a prescribed route, which
includes CEVMS installations, standard (non-digital) billboards, human-constructed objects of
casual visual interest (houses, barns, etc.), and natural background control scenery (trees, fields,
etc.). Each drive takes less than 1 hour (preferably about 30 minutes), and each participant would
return for several drives on different days. Other aspects would vary as well, such as the time of
day, traffic density, and CEVMS conditions (e.g., CEVMS turned on versus CEVMS turned off).
Each participant would complete between three and six such drives. The instrumented vehicle
and crew would usually remain at a given study site for about 1 to 2 months. The crew would
consist of an experimenter and a safety observer, who would both be present in the instrumented
vehicle. The safety observer would also serve as a research assistant or technician. The
instrumented vehicle is capable of measuring vehicle speed, vehicle lane position, longitudinal
acceleration, lateral acceleration, GPS time and position, and driver eye glance direction and
duration. The instrumented vehicle is also equipped with accurate vehicle-mounted or headmounted
eye-tracking equipment, video cameras (forward and cab views) and a voice recorder.
B.1.2 Factors and Measures
The major factors or independent variables in the study are the presence or absence of CEVMS
and other comparison visual stimuli (standard billboards, buildings, etc.) along the driving path.
If possible, the CEVMS should be capable of being turned off and on or changed along some
other dimension like luminance or change rate, according to a prearranged experimental design.
The period of time that the CEVMS is off or changed could be kept relatively brief and carefully
controlled since the study will follow a strict protocol. Other important independent variables are
the time of day (day/night), traffic conditions (peak and nonpeak), and driver variables (age,
gender, and route familiarity). One or more of the primary CEVMS variables of interest to the
community concerned with outdoor advertising control should be represented by varying levels
along the driving route (e.g., different degrees of luminance, change rate, or display spacing) as
much as possible. Direct experimental control would be preferable to site selection in this regard.
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