6. HIGHWAY SAFETY APPLICATIONS

            This Chapter focuses on highway-safety discussions primarily on highway-rail grade crossings, pedestrian and bicycle safety, intersection safety, speed management, and work zone safety. As such, the opportunities for ADUS highway safety applications discussion in this report are those that can contribute to addressing issues facing the aforementioned safety areas. The opportunities for ADUS public safety applications and transit safety and securing application are discussed in chapters 4 and 7, respectively.

            Highway safety is perhaps the area that is targeted the least in terms of data archiving. Nonetheless, because highway safety is a complex interaction among vehicles, roadways, environments and drivers, highway safety is also the area that will benefit the most from data archiving. Since highway safety transcends geographic boundaries (metropolitan vs. rural), data archived from almost any of the ITS infrastructure components (e.g., traffic surveillance) can be used to meet some of the data requirements in highway safety applications. For example, volume data collected from an ITS traffic surveillance project can be used to estimate accident exposure by time of day and day of the week. Another example is archived speed data which, in conjunction with information on highway geometry and weather, can be used to estimate the propensity of incidents or accidents. That said, data integration becomes ever more imperative in highway safety applications.

6.1 STATE-OF-THE-PRACTICE REVIEW

            Almost all of the data elements collected by the Freeway and Arterial Management Surveys can be used to fill data gaps in highway safety, particularly the exposure aspects of highway safety. From the highway safety perspective, exposure information categorized by different vehicle types is equally important to information on overall vehicle exposure.

            Based on the information collected from the ITS Deployment Tracking Surveys, by far the most commonly collected freeway data are: traffic volume, and information on scheduled work zones (Figure 6.1). The most common technique used to collect traffic data is loop detectors, followed by video imaging detectors. Figure 6.2 depicts the prominence of different techniques used to collect traffic data. It is obvious from this figure that less intrusive technologies are becoming popular in collecting traffic data. Traffic volume and vehicle classification data which are essential in deriving vehicle-type specific exposure data are the two data elements that are most likely to be archived. Eighty-seven percent of the agencies in 1999 that collected traffic volume data also archive them. And, seventy-six percent of the agencies that collect vehicle classification data also archive them (Table 6.1).

Figure 6.1 Freeway Data Generation and Archiving

(Out of 74 Agencies Reported Data Generation and Archiving in 1999. 

Out of 66 Agencies Reported Data Generation and Archiving in 2000)

Figure 6.2 Techniques to Generate Traffic Data

1999 and 2000 ITS Deployment Tracking Surveys 

            * These questions were not asked in 2000

           Other data elements specifically pertinent to highway safety are:

            ●          Information on current and scheduled work zones. Almost three quarters of the agencies that collected this information archive it.

            ●          Weather and roadway conditions. Weather conditions and road conditions are archived by at least half of the agencies that collect/report weather and road conditions as part of their Freeway Management Systems as well as their Arterial Management Systems.

            ●          Information on ramp metering strategies help understand the propensity of side swipes and rear-end collisions on ramps.

            ●          Data archived on emergency responses and emergency vehicle signal preemption provide a foundation to evaluate the effectiveness of emergency management controls in saving lives.

            ●          Information on traffic signal controls (turning movements, phasing and cycle lengths and queues) advances knowledge about the causes of intersection accidents.

            ●          Pedestrian and bicycle traffic at intersections.

            Tables 6.2 and 6.3 show the propensity for data archiving in 1999 and 2000, with a significant downward trend. No agencies collect all seventeen data elements identified on the survey questionnaire. In 1999 one agency collected 14 out of the 17 data elements and it archived every data element collected. Overall, 31 of the 78 agencies in 1999 archived all of the traffic data collected (cells on the diagonal line) while the corresponding numbers are 19 out of 66 agencies in year 2000. Ten agencies in 1999 and eight agencies in 2000 reportedly collected traffic data but did not archive any (the “0“ column).

Table 6.2 Distribution of Agencies by Number of Data Elements Generated and Number of Data Elements Archived

1999 ITS Deployment Tracking Survey

Table 6.3 Distribution of Agencies* by Number of Data Elements Generated and Number of Data Elements Archived

2000 ITS Deployment Tracking Survey