Road Safety Performance Associated with Improved Traffic Signal Design and Increased Signal Conspicuity

8.0 Results and Discussion

By utilizing the methodology described in the preceding section, the treatment effects can be calculated for each improvement site. Table 3 below shows the results for the reductions in the total claims for the 25 sites.

Table 3: Reductions Factors for each Improvement Site

ID No.	Site Type	Major Road	Minor Road	City Location	Claims Reduction1.
1	Treatment	Rte 17	Halibuton	Saanich	-25.5%
2	Treatment	Rte 17	Island View	Saanich	-5.5%
3	Treatment	Rte 17	Beacon	Saanich	-8.2%
4	Treatment	Rte 1	Morden	Nanaimo	-21.0%
5	Treatment	Rte 1	Cedar Rd N.	Nanaimo	-23.4%
6	Treatment	Rte 19	College Rd	Nanaimo	-24.9%
7	Treatment	Rte 19	Jingle Pt	Nanaimo	6.1%
8	Treatment	Rte 19	Northfield	Nanaimo	-11.7%
9	Treatment	Rte 19	Molstar/Jingle	Nanaimo	4.3%
10	Treatment	Rte 19	Aulds	Nanaimo	16.8%
11	Treatment	Rte 19	Ware	Nanaimo	-51.0%
12	Treatment	Rte 19	Cook Creek	Qualicum	-38.3%
13	Treatment	Rte 19	Cliff	Courtney	-2.8%
14	Treatment	Rte 19	Comox	Courtney	-60.7%
15	Treatment	Rte 19	Ryan	Courtney	-15.4%
16	Treatment	Rte 19	26th St	Courtney	-60.7%
17	Treatment	Rte 97	Rt 33	Kelowna	-5.5%
18	Treatment	Rte 97	Prairie Valley	Summerland	20.6%
19	Treatment	Rte 97	Rosedale	Summerland	2.9%
20	Treatment	Rte 97	Banks	Kelowna	-16.9%
21	Treatment	Rte 97A	Smith	Armstrong	-21.0%
22	Treatment	Rte 97A	Cliffe	Enderby	-47.2%
23	Treatment	Rte 16	1st Ave	Prince George	3.0%
24	Treatment	Rte 17	17th Ave	Prince George	-54.0%
25	Treatment	Rte 18	20th Ave	Prince George	-22.3%
Total Overall					-14.8%

^1.A negative value indicates a reduction

Of the 25 sites that were and investigated in this study, a total of 19 sites have shown a reduction in the number of claims after the implementation of the improvements to the conspicuity of the signal head backboard. The magnitude of the reduction in claim frequency ranged from a low of 2.8 percent to a high of 60.7 percent. Overall, it is estimated that the improvements to the signal head backboard will result in a 14.8 percent reduction in the total number of claims at an improved intersection. A total of 6 of the 25 improvement sites experienced an increase in the number of claims after the improvements to the signal head, with the magnitude of the increase ranging from a low of 2.9 percent to a high of 20.6 percent. These results are shown graphically below in Figure 4.

Figure 4. Reduction in the Total Claims at Treatment (Improved) Sites

As mentioned earlier, this current phase of the study represents the follow-up from an original study (phase 1) undertaken by Sayed in 1998 (Sayed et. al, 1998(1)). A similar methodology was used in the original study, with the exception that a reference group was used to account for the regression to the mean bias instead of the prediction model that was used in this study. In addition, the original study utilized collision data and not claims data. Based on 10 treatment sites in phase 1 of the study, Sayed reported a reduction of 24 percent in the total number of accidents. This result is considered to be consistent with the results of this study (i.e., 15 percent reduction), given the noted differences between the two studies.

There are several opportunities to expand the safety analysis, which will be completed and published at a later date. These opportunities include increasing the number of treatment sites, disaggregating the safety performance analysis into high severity claims (fatal and injury) and low severity claims (property damage only), determining the economic justification (i.e., benefit-cost ratios) for the signal head backboard upgrade, and evaluating the reliability of the results (Sayed and de Leur, 2001).

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