The Effects of Commercial Electronic Variable Message Signs ...

Variable Ref. # Advantages Disadvantages
3.2.2 Conspicuity; attention
grabbing
3.2.3 Search patterns 15 Indicative of visual
hypotheses.
3.2.4 Capacity: selfregulated
attention; spare
capacity
3.3 Subjective measures 161
15 Extremely important
concept.
51
Difficult to measure.
Hard to establish criterion
threshold.
3.3.1 Conversational drive Good possible method. Lots of extraneous data.
3.3.2 Rating scale Inexpensive. Imprecise.
3.3.3 Questionnaire Inexpensive. Imprecise.
3.3.4 Survey 125 Relatively inexpensive. Sampling frame difficult.
3.3.5 Focus group Small sample. Lots of data. Confounding social
variables.
4.0 Crashes 158, 125,
26, 44,
128, 161,
95, 121
4.1 Type: head-on;
sideswipe; rear-end;
backing; run-off-road;
pedestrian
4.2 Severity: fatal; injury;
property damage;
unreported
4.3 Method of
measurement
4.3.1 Direct observation:
simulator; field camera
39 Very important
discriminator variable.
Related to ultimate goal.
Important to determine
impact.
42 Best studied in simulator.
No chance of injury.
Rare events. Many
contributing factors. Difficult
to estimate statistically.
Rare events. Many factors.
Difficult to estimate
statistically.
Rare events. Hard to
estimate.
4.3.2 Before/after study 39, 158 Most common study type. No control site. Regression
toward mean.