Effectiveness of Safety and Public Service Announcement Messages on Dynamic Message Signs

CHAPTER 6. Findings and Recommendations/Guidance

Summary data showed that respondents do take assertive PSAs quite seriously (e.g., monetary fine and number of deaths). In Philadelphia, respondents appeared to be more uncomfortable with messages that include direct consequences (e.g., drink and you will go to jail), when compared to Chicago and Houston. This could be due to the fact that those that drive in Chicago and Houston are more accustomed to seeing these message displays as compared to Philadelphia. Respondents in all four cities indicated that PSAs that show a monetary fine would impact their driving, as would data displayed on number of crashes.

There were two inferential models developed. Table 29 summarizes the findings from the four models developed to assess the usefulness of PSAs on DMS; an up arrow corresponds to “perceived as more useful,” a down arrow corresponds to “perceived as less useful,” and ‘ns’ corresponds to “not a significant variable within that location.” Four models were developed to observe the differences within each city. All factors in Philadelphia had an increasing effect on perceived usefulness; however, this was not observed in any other city. It is important to note that encountering PSAs often and considering PSAs effective increased perceived usefulness at all locations. In addition, two locations observed respondents younger than 30 year old to consider PSAs not useful.

Table 29. Perceived usefulness of PSAs on DMS summary.
Perceived Usefulness	Location
Perceived Usefulness	Philadelphia	Orlando	Chicago	Houston
Encounters PSAs often
PSAs on DMS are effective
PSAs on seatbelts are important		ns	ns	ns
PSAs on DUI are important		ns
PSAs on speeding are important	ns
Lives within greater area	ns	ns		ns
Male			ns	ns
Younger than 30 years old	ns	ns
Older than 60 years old	ns	ns		ns
Some high school or high school diploma	ns	ns	ns
Some graduate school or postgraduate degree	ns	ns	ns
Income less than $25,000 per year	ns	ns		ns
Has been in at least 1 crash within 5 years	ns	ns		ns
Has received at least 1 ticket within 5 years	ns		ns	ns

Another model was designed to examine the effectiveness of PSAs when compared to other media types (e.g., radio, billboard, TV), and this model was based on data pooled from all four cities. In this latter model, a smaller subset of data was used. More specifically, this model captured only data that was identical in all four cities. This summary is provided in Table 30, where up arrows indicate factors that increased perceived effectiveness and down arrows represent factors that decrease perceived effectiveness. Insignificant variables are not included in this summary.

Table 30. Perceived effectiveness of PSAs on DMS summary.
Perceived Effectiveness	Effect
Encounters PSAs often
PSAs on DMS are useful
Male with income less than $25,000 per year
Younger than 30 years old
Older than 60 years old
Some graduate school or postgraduate degree

Respondents were provided with specific PSAs commonly displayed on DMS in their city and asked whether they would change their driving behaviors when they saw those messages.

In Orlando, the largest proportion of responses stipulated that drivers would definitely change their driving behaviors when they saw all nine example messages.
In Chicago, the majority of responses were that all eight messages would probably or definitely change their driving behaviors. The messages with the largest impact on driving were about slowing down for work zones and emergency vehicles.
The eight example messages in Philadelphia had the largest number of responses in the “maybe” to “probably” changing driving behaviors.
Houston respondents reported the least amount of consistency in behavioral changes from their nine example messages. The only two messages with a majority response were “Drunk driving, over the limit, under arrest” and “100 deaths this year on Texas road,” based upon which drivers would definitely change their behaviors. It is to be noted that these were the only two messages with assertive language.

The assumption is that most survey respondents spoke English and had an 8th grade education level. Considering the population of survey respondents, this assumption appears to hold true as the majority did indicate English as their primary language, and the majority did indicate that they had some high school education or higher. Hence, many of the words used in the survey were not defined (e.g., distraction, safety, consequence). Based on earlier meetings with the state transportation agencies, it was deemed important to separate usefulness from effectiveness. Although the survey did not define usefulness or effectiveness to the survey respondents, the goal was to consider usefulness as a practical and functional application of PSAs on DMS. Effectiveness captured the perception that DMS were the most successful medium to deliver PSAs in a way that would impact driver behavior.

In general, most respondents across the four cities indicated that PSAs on DMS appear useful. Respondents with an income lower than $25,000 annually did not find these messages to be useful, but this effect was observed in Houston only. Respondents who have been in a crash or had received a ticket in the past 5 years were less likely to find PSAs to be useful.

When aggregated across all four cities, producing a larger sample size, young males with lower incomes tend not to find these messages effective. Older drivers and drivers with a higher education found safety and PSA messages on DMS to be effective, while younger drivers did not.

Traditionally, DMS are used to provide useful travel information to drivers so that they know whether they need to change routes, reduce speed, or change lanes. This study showed that there could be some possibility of changing driver behavior if safety and PSA messages were also posted on DMS. For example, those drivers who reported that certain safety issues are important to disseminate (e.g., driving under the influence or staying below the speed limits) also found PSAs to be both useful and effective. However, it would be very important to ensure that PSAs that are placed on DMS are both useful and effective. Hence, more testing and studies would be needed to validate whether the perceptions noted in the surveys translate to real-world driving. Often, drivers’ stated preferences differ from their revealed preferences. Another concern that should be tested on-road is whether the inclusion of additional PSAs would be more distracting to travelers, impacting their overall safety. Lastly, there is a cost associated with operating DMS in terms of maintenance and use. Again, these issues would need to be examined in the real world. Table 31 provides some overall recommendations based on the study’s key findings.

Table 31. PSAs on DMS—recommendations and guidance.
Findings	Recommendations/Guidance
Assertive PSAs (e.g., monetary fine and number of deaths) are taken seriously	Assertive PSAs need to be examined more carefully to identify the impact on driver behavior.
PSAs that show a monetary fine impact driving	It is uncertain whether including monetary fines has a good or bad impact on driving. Hence, PSAs that show monetary fines need to be examined on-road.
PSAs that include data on crash statistics impact driving	It is uncertain whether including crash statistics will have a good or bad impact on driving. Hence, PSAs that show crash statistics need to be examined on-road before further implementation.
There is an association between the frequency of observation of PSAs on DMS and the perceived usefulness	More studies need to be done to pinpoint the appropriate number and frequency of PSAs on DMS to avoid the introduction of an unnecessary number of messages.
Younger respondents (less than 30) are less likely to consider PSAs on DMS effective	Promote awareness on (and familiarity with) PSAs among the younger groups of population.

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