4. Non-Signalized Intersections

Separate ranked lists were developed for non-signalized intersections, in part because signalization might be a mitigating strategy. Also, certain intersection safety problems are exclusive to signalization, such as dilemma zones and red light violations. Further, non-signalized locations might be associated with non-stop, high-speed traffic on the uncontrolled approaches, behavioral issues related to stop and yield signs, and choices and differences in gap acceptance. The intersections are listed in Tables 4.1-4.4 for 10- and 3-year study periods, based on the total number of crashes and the crash severity score. The research team did not distinguish between different types of non-signalized intersection, such as three-legged or four-legged, two-way stop, four-way stop, yield sign, and so forth.

An examination of Tables 4.1-4.4 reveals that all of the intersections are located along heavily-used roads in Regions 1, 2, 3 or 4 (Cedar City District). In many cases, the cross-street is a collector or local facility, and the major street has the right-of-way. Also, in many cases, the intersection is located near a signalized intersection. In fact, in some of these cases, the crash activity may be associated with "spillover" from the signalized intersection (although the research team excluded from consideration non-signalized intersections that were clearly within the functional area of influence of a nearby signalized intersection; in general, the spacing between these intersections was less than 500 ft). Because of the adjacency of one or more signalized intersections in many of these cases, signalization may not be a feasible strategy. Other approaches, such as turning restrictions, traffic calming devices, and speed limit modifications may need to be considered. The research team did not perform a close investigation of these intersections; site-specific studies would be recommended. The traffic signal warrants in the MUTCD would need to be evaluated. It is likely that a majority of the intersections listed in Tables 4.1-4.4 would satisfy the crash criteria in the 6th warrant ("accident experience").

As suggested above, the intersections listed in the four tables are dominated by two-way stop-controlled junctions between a major road and a minor cross-street. It would be of interest to compile separate rankings for other types of non-signalized intersections, including four-way stops, yield sign-controlled locations, T-intersections, and rotaries. Also, Weerasuriya and Pietrzyk (1998) found that the intersection configuration (e.g., number of lanes by approach) was a factor in predicting conflicts. Further, Kaysi and Alam (2000) found that factors such as driver learning, impatience, aggression, and complex gap acceptance were key explanatory variables in predicting the "quality of traffic service" at an unsignalized intersection. Regarding the latter factor, the authors noted that the "mode" of the traffic stream (i.e., the vehicle arrival stream) influenced the gap acceptance behavior of drivers. The behavior became increasingly complex as the conflicting traffic stream became more voluminous with reduced "platooning." A deeper investigation of the intersections listed in Tables 4.1-4.4 was beyond the scope of this study, but the need for examinations in the field is clear.

A total of 21 intersections appear on both the 10-year and 3-year lists based on total number of crashes. The high number of "repeat" intersections suggests that there were few or no improvements at these locations during the study periods. The large number also suggests that signal control may be a mitigating strategy, based on the hypothesis that the crashes occurring at these intersections are related to the lack of signalization. A total of eight intersections appear on both the 10-year and 3-year lists based on crash severity scores. These intersections may also be candidates for signal control. Between four and 15 intersections in each of Tables 4.1-4.4 also appear in the statewide "top 50" lists (Tables 2.2-2.5). These intersections' appearances on the statewide lists might be a further criterion for mitigation, including signalization. The following two intersections appear in all four tables (Tables 4.1-4.4):

• 3300 South and Sue Street (30 West) (SR 171 at milepoint 10.54 - South Salt Lake).
• 3300 South and Edison Street (145 East) (SR 171 at milepoint 10.83 - South Salt Lake).

These intersections are explored in greater deal in Section 6.