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APPENDIX C. DETAILED EVALUATION RESULTS

This appendix presents the detailed results of the evaluation of the effectiveness of left- and right-turn lane improvement projects performed in this study. The results for the yoked comparison (YC), comparison group (CG), and Empirical Bayes (EB) approaches are presented separately. This appendix presents the results of all evaluations that were performed. Only those results that were found to be statistically significant are presented and interpreted in the main text of this report (see section 6).

Yoked Comparison Evaluations

The results of the YC evaluations performed in this study are presented in tables C-1 through C-10. These tables include the results for four specific dependent variables, two different target areas, and two different types of analysis approaches.

The YC approach to before-after evaluation has been described conceptually in section 5 of this report. The procedures presented in that section were used to obtain the analysis results in tables C-1 through C-10. These analyses involved one-to-one matching of treatment and similar unimproved comparison sites. Two analyses presented below involved only treatment site data; in this approach, the project-related accidents for the treatment site were evaluated using the non-project-related accidents for that same site as the "comparison site" data. These were referred to as auto-matching analyses.

Description of Results Tables

Each of the tables of YC results presents the results of a set of similar YC evaluation for a specific dependent variable, target area, and analysis type. Each row in a table presents the results of the evaluation performed for a specific type of improvement project. The following discussion guides the interpretation of individual columns in these tables.

Area type. The first column for each row of the table identifies the area type for the intersections evaluated. The codes used in this column are:

R = rural
U = urban

Traffic control: The second column identifies the type of traffic control at the intersections evaluated. The codes used in this column are:

N = Newly signalized intersection
S = Signalized intersection
U = Unsignalized intersection

Table C-1. Yoked Comparison Evaluation Results for Total Intersection Accidents.
Area type Traffic control Project type No. of legs No. of improved sites Percent change in accident frequency Treatment effect Test for homogeneity
Mean Mean per added lane Standard error Lower 95% confidence limit Upper 95% confidence limit Ratioa Calculated Z Significant at 5% level? Calculated H probability Homogeneous at 5% level?
R N L 4 2 -70.31 -35.15 7.60 -44.56 -9.52 4.63 -2.37 SIG 0.39 Yes
R N LR 4 1 8.58 4.29 65.60 -44.92 529.83 0.07 0.07 n/a   n/a
R N R 4 1 -10.38 -5.19 20.07 -31.38 57.82 0.26 -0.24 n/a   n/a
R S XL 3 2 -27.76 -27.76 54.20 -83.40 214.40 0.51 -0.43 NS 0.41 Yes
R S XL 4 3 -30.64 -30.64 27.62 -68.21 51.37 1.11 -0.92 NS 0.87 Yes
R S XLR 4 1 -44.32 -11.08 7.85 -20.39 17.07 1.41 -1.04 n/a   n/a
R U L 3 31 -63.68 -63.68 7.21 -75.39 -46.41 8.83 -5.10 SIG 0.20 Yes
R U L 4 21 -58.08 -32.10 4.70 -39.70 -20.78 6.83 -4.28 SIG 0.04 No
R U LR 3 11 -56.64 -44.50 15.08 -64.27 2.57 2.95 -1.89 NS 0.76 Yes
R U LR 4 12 1.96 0.98 13.39 -19.53 35.31 0.07 0.07 NS 0.74 Yes
R U R 3 11 88.66 88.66 77.59 -15.75 322.45 1.14 1.54 NS 0.86 Yes
R U R 4 27 -23.91 -15.37 10.99 -32.80 11.69 1.40 -1.22 NS 0.86 Yes
R U XL 4 1 82.06 82.06 222.08 -83.33 1,888.76 0.37 0.49 n/a   n/a
U N L 3 4 -30.29 -20.19 14.09 -41.01 17.52 1.43 -1.19 NS 0.02 No
U N L 4 24 -43.77 -22.35 3.18 -27.95 -15.39 7.03 -5.20 SIG 0.03 No
U S L 3 3 -32.62 -32.62 30.80 -72.49 65.08 1.06 -0.86 NS 0.18 Yes
U S L 4 33 -42.00 -12.95 1.16 -15.09 -10.53 11.17 -8.40 SIG 0.00 No
U S LR 4 9 -21.25 -5.46 2.20 -9.35 -0.65 2.48 -2.20 SIG 0.01 No
U S R 3 1 -36.52 -18.26 15.54 -37.84 32.85 1.18 -0.93 n/a   n/a
U S R 4 14 -13.65 -6.82 4.23 -14.37 2.32 1.61 -1.50 NS 0.00 No
U S XL 3 1 -25.11 -25.11 43.24 -75.85 132.21 0.58 -0.50 n/a   n/a
U S XL 4 2 14.95 9.97 15.24 -14.77 46.50 0.65 0.70 NS 0.80 Yes
U U L 3 10 -36.55 -36.55 17.52 -63.07 9.00 2.09 -1.65 NS 0.28 Yes
U U L 4 8 -70.46 -35.23 2.92 -39.97 -28.24 12.07 -6.17 SIG 0.63 Yes
U U LR 4 1 -0.85 -0.42 37.06 -38.55 164.58 -0.01 0.01 n/a   n/a
U U R 4 1 22.76 22.76 228.29 -96.79 4,599.26 0.10 0.11 n/a   n/a

a Ratio of mean percent change in accident frequency to standard error of percent change in accident frequency per turn lane installed.

Table C-2. Yoked Comparison Evaluation Results for Fatal and Injury Intersection Accidents.
Area type Traffic control Project type No. of legs No. of improved sites Percent change in accident frequency Treatment effect Test for homogeneity
Mean Mean per added lane Standard error Lower 95% confidence limit Upper 95% confidence limit Ratioa Calculated Z Significant at 5% level? Calculated H probability Homogeneous at 5% level?
R N L 4 2 -82.61 -41.31 6.58 -48.03 -11.64 6.27 -2.31 SIG 0.69 Yes
R N LR 4 1 -3.95 -1.97 61.88 -46.16 550.18 0.03 -0.03 n/a   n/a
R N R 4 1 -2.86 -1.43 32.03 -36.67 126.92 0.04 -0.04 n/a   n/a
R S XL 3 2 -35.44 -35.44 63.34 -90.56 341.70 0.56 -0.45 NS 0.72 Yes
R S XL 4 3 63.45 63.45 85.33 -41.25 354.74 0.74 0.94 NS 0.98 Yes
R S XLR 4 1 18.67 4.67 24.66 -19.18 126.30 0.19 0.21 n/a   n/a
R U L 3 34 -58.55 -58.55 11.78 -76.26 -27.63 4.97 -3.10 SIG 0.78 Yes
R U L 4 22 -70.41 -39.72 4.85 -46.97 -26.90 8.18 -4.19 SIG 0.88 Yes
R U LR 3 11 -51.67 -40.60 22.18 -66.48 40.71 1.83 -1.25 NS 0.99 Yes
R U LR 4 14 -7.72 -3.86 16.19 -26.80 41.77 0.24 -0.23 NS 0.98 Yes
R U R 3 11 18.83 18.83 62.88 -57.88 235.23 0.30 -0.33 NS 1.00 Yes
R U R 4 28 -22.28 -14.51 15.09 -36.91 25.69 0.96 -0.85 NS 0.94 Yes
R U XL 4 2 156.22 156.22 335.09 -80.26 3,225.51 0.47 0.72 NS 0.27 Yes
U N L 3 4 -10.57 -7.04 28.32 -43.17 84.60 0.25 -0.24 NS 0.11 Yes
U N L 4 23 -42.68 -21.81 5.40 -30.70 -9.05 4.04 -3.02 SIG 0.67 Yes
U S L 3 3 -41.97 -41.97 40.03 -84.99 124.28 1.05 -0.79 NS 0.25 Yes
U S L 4 35 -39.35 -12.41 2.04 -16.01 -7.96 6.08 -4.69 SIG 0.00 No
U S LR 4 8 -27.75 -7.16 3.75 -13.23 1.84 1.91 -1.62 NS 0.36 Yes
U S R 3 1 -74.25 -37.13 12.09 -47.96 31.17 3.07 -1.44 n/a   n/a
U S R 4 12 -20.22 -9.71 7.22 -21.54 7.41 1.34 -1.20 NS 0.38 Yes
U S XL 3 1 -0.14 -0.14 99.86 -85.93 608.91 0.00 0.00 n/a   n/a
U S XL 4 3 -7.71 -4.62 19.19 -31.92 49.21 0.24 -0.23 NS 0.14 Yes
U U L 3 10 -41.59 -41.59 24.13 -74.01 31.27 1.72 -1.30 NS 0.67 Yes
U U L 4 8 -79.48 -39.74 3.04 -44.26 -31.65 13.06 -5.34 SIG 0.93 Yes
U U LR 4 1 -73.75 -36.88 18.17 -49.13 147.92 2.03 -0.97 n/a   n/a
U U R 4 1 84.14 84.14 379.61 -96.76 10,370.69 0.22 0.30 n/a   n/a

a Ratio of mean percent change in accident frequency to standard error of percent change in accident frequency per turn lane installed.

Table C-3. Yoked Comparison Evaluation Results for Project-Related Intersection Accidents.
Area type Traffic control Project type No. of legs No. of improved sites Percent change in accident frequency Treatment effect Test for homogeneity
Mean Mean per added lane Standard error Lower 95% confidence limit Upper 95% confidence limit Ratioa Calculated Z Significant at 5% level? Calculated H probability Homogeneous at 5% level?
R N L 4 2 -33.84 -16.92 44.21 -47.59 404.14 0.38 -0.31 NS 1.00 Yes
R N LR 4 1 -47.97 -23.99 68.83 -49.85 4,598.55 0.35 -0.25 n/a   n/a
R N R 4 1 0.01 0.00 141.41 -49.80 12,730.59 0.00 0.00 n/a   n/a
R S XL 3 2 -7.57 -7.57 184.85 -98.17 4,558.33 0.04 -0.04 NS 0.98 Yes
R S XL 4 4 23.06 23.06 119.45 -81.64 724.77 0.19 0.21 NS 0.99 Yes
R S XLR 4 1 -2.90 -0.73 47.01 -24.45 1,055.24 0.02 -0.02 n/a   n/a
R U L 3 34 -1.04 -1.04 47.90 -61.68 155.56 0.02 -0.02 NS 1.00 Yes
R U L 4 23 -38.43 -21.56 16.71 -42.72 33.06 1.29 -1.00 NS 1.00 Yes
R U LR 3 12 -15.23 -12.18 53.44 -65.53 237.78 0.23 -0.21 NS 1.00 Yes
R U LR 4 15 68.38 34.19 44.25 -19.95 185.88 0.77 0.99 NS 0.95 Yes
R U R 3 11 4.90 4.90 89.46 -80.28 458.06 0.05 0.06 NS 1.00 Yes
R U R 4 28 -7.41 -4.83 28.83 -41.50 88.81 0.17 -0.16 NS 1.00 Yes
R U XL 4 2 50.26 50.26 242.29 -93.63 3,443.23 0.21 0.25 NS 0.57 Yes
U N L 3 4 -32.95 -21.97 59.60 -63.39 543.20 0.37 -0.30 NS 0.99 Yes
U N L 4 26 22.55 11.73 23.61 -21.17 79.74 0.50 0.55 NS 0.76 Yes
U S L 3 3 0.06 0.06 155.01 -95.20 1,984.29 0.00 0.00 NS 1.00 Yes
U S L 4 35 -39.09 -12.55 3.17 -17.87 -5.25 3.96 -3.06 SIG 0.53 Yes
U S LR 3 2 222.83 148.55 351.45 -57.90 5,216.77 0.42 0.72 NS 0.96 Yes
U S LR 4 7 -59.77 -15.50 2.24 -19.09 -10.02 6.90 -4.23 SIG 0.84 Yes
U S R 3 1 -46.90 -23.45 35.12 -48.01 304.93 0.67 -0.48 n/a   n/a
U S R 4 13 9.10 5.38 19.84 -23.82 58.74 0.27 0.28 NS 0.00 No
U S XL 3 1 299.43 299.43 1,018.34 -97.30 59,004.76 0.29 0.54 n/a   n/a
U S XL 4 2 5.15 3.44 118.54 -64.12 1861.12 0.03 0.03 NS 0.78 Yes
U U L 3 10 12.61 12.61 100.01 -80.25 542.02 0.13 0.13 NS 1.00 Yes
U U L 4 8 -78.97 -39.49 4.87 -45.76 23.93 8.11 -3.37 SIG 0.57 Yes
U U LR 4 1 162.46 81.23 215.63 -44.76 3236.40 0.38 0.59 n/a   n/a
U U R 4 1 -7.93 -7.93 260.41 -99.64 23,435.42 0.03 -0.03 n/a   n/a

a Ratio of mean percent change in accident frequency to standard error of percent change in accident frequency per turn lane installed.

Table C-4. Yoked Comparison Evaluation for Project-Related Fatal and Injury Intersection Accidents.
Area type Traffic control Project type No. of legs No. of improved sites Percent change in accident frequency Treatment effect Test for homogeneity
Mean Mean per added lane Standard error Lower 95% confidence limit Upper 95% confidence limit Ratioa Calculated Z Significant at 5% level? Calculated H probability Homogeneous at 5% level?
R N L 4 2 -28.78 -14.39 57.63 -48.51 799.48 0.25 -0.21 NS 0.83 Yes
R N LR 4 1 -47.97 -23.99 68.83 -49.85 4,598.55 0.35 -0.25 n/a   n/a
R N R 4 1 -0.01 0.00 141.41 -49.80 12,730.59 0.00 0.00 n/a   n/a
R S XL 3 2 -7.57 -7.57 184.85 -98.17 4,558.33 0.04 -0.04 NS 0.98 Yes
R S XL 4 4 177.73 177.73 311.15 -69.10 2,396.19 0.57 0.91 NS 0.86 Yes
R S XLR 4 1 45.65 11.41 80.05 -24.51 2,682.84 0.14 0.17 n/a   n/a
R U L 3 34 1.31 1.31 49.14 -60.85 162.14 0.03 0.03 NS 1.00 Yes
R U L 4 23 -36.33 -20.38 18.87 -43.42 44.50 1.08 -0.85 NS 1.00 Yes
R U LR 3 12 -17.33 -13.87 53.37 -66.40 241.59 0.26 -0.24 NS 1.00 Yes
R U LR 4 15 -4.91 2.46 30.40 -36.42 116.47 0.08 -0.08 NS 1.00 Yes
R U R 3 11 4.90 4.90 89.46 -80.28 458.06 0.05 0.06 NS 1.00 Yes
R U R 4 28 -4.40 -2.87 31.87 -42.30 104.69 0.09 -0.09 NS 1.00 Yes
R U XL 4 2 143.69 143.69 451.22 -93.53 9,082.86 0.32 0.48 NS 0.73 Yes
U N L 3 4 -3.68 -2.46 90.81 -62.65 959.95 0.03 -0.03 NS 1.00 Yes
U N L 4 26 -8.78 -4.57 22.33 -33.14 67.33 0.20 -0.20 NS 1.00 Yes
U S L 3 3 1.06 1.06 165.02 -95.88 2,380.82 0.01 0.01 NS 1.00 Yes
U S L 4 35 -32.67 -10.49 6.31 -19.91 6.21 1.66 -1.35 NS 1.00 Yes
U S LR 3 2 -25.28 -16.86 96.24 -65.54 2,131.34 0.18 -0.15 NS 0.89 Yes
U S LR 4 8 -49.63 -12.81 4.96 -19.65 1.64 2.58 -1.80 NS 0.65 Yes
U S R 3 1 -73.45 -36.72 33.85 -49.91 1,914.45 1.09 -0.52 n/a   n/a
U S R 4 14 40.32 20.16 30.02 -19.67 112.29 0.67 0.79 NS 0.59 Yes
U S XL 3 1 99.71 99.71 528.39 -98.88 35,587.40 0.19 0.26 n/a   n/a
U S XL 4 3 34.97 20.98 109.53 -54.29 1,087.46 0.19 0.22 NS 0.79 Yes
U U L 3 10 3.97 3.97 92.99 -81.99 500.14 0.04 0.04 NS 1.00 Yes
U U L 4 8 -81.50 -40.75 5.62 -47.19 -19.58 7.25 -2.78 SIG 0.95 Yes
U U LR 4 1 -47.51 -23.75 69.44 -49.85 4,639.94 0.34 -0.24 n/a   n/a
U U R 4 1 -7.93 -7.93 260.41 -99.64 23,435.42 0.03 -0.03 n/a   n/a

a Ratio of mean percent change in accident frequency to standard error of percent change in accident frequency per turn lane installed.

Table C-5. Yoked Comparison Evaluation Results for Total Accidents on Individual Intersection Approaches.
Area type Traffic control Project type No. of legs No. of improved sites Percent change in accident frequency Treatment effect Test for homogeneity
Mean Mean per added lane Standard error Lower 95% confidence limit Upper 95% confidence limit Ratioa Calculated Z Significant at 5% level? Calculated H probability Homogeneous at 5% level?
R N L 4 4 -67.45 -67.45 9.33 -44.71 0.07 3.61 -1.96 SIG 0.65 Yes
R N LR 4 2 -11.77 -5.88 47.18 -44.58 308.79 0.12 -0.12 NS 0.78 Yes
R N R 4 2 -7.11 -7.11 23.17 -32.53 73.49 0.15 -0.15 NS 0.49 Yes
R S XL 3 2 61.29 61.29 189.96 -83.96 1,522.35 0.32 0.41 NS 0.62 Yes
R S XL 4 4 -50.86 -50.86 26.61 -83.00 42.03 1.91 -1.31 NS 0.69 Yes
R S XLR 4 2 -39.42 -19.71 7.49 -14.31 26.55 0.88 -0.68 NS 0.41 Yes
R U L 3 34 -47.46 -47.46 16.56 -71.67 -2.55 2.87 -2.04 SIG 0.61 Yes
R U L 4 40 -47.32 -47.32 6.35 -35.29 -9.58 3.97 -2.84 SIG 0.70 Yes
R U LR 3 23 -51.34 -25.67 18.04 -63.87 17.14 2.26 -1.54 NS 0.99 Yes
R U LR 4 27 5.26 2.63 14.21 -19.00 39.36 0.19 0.19 NS 0.99 Yes
R U R 3 11 79.25 79.25 107.95 -44.94 483.59 0.73 0.97 NS 1.00 Yes
R U R 4 43 -18.72 -18.72 11.48 -28.98 17.69 0.96 -0.86 NS 1.00 Yes
R U XL 4 1 0.00 0.00 193.65 -97.75 4,350.15 0.00 0.00 n/a   n/a
U N L 3 6 -25.86 -25.86 19.80 -41.41 46.43 0.78 -0.67 NS 0.24 Yes
U N L 4 47 -55.50 -55.50 3.36 -34.08 -20.70 8.43 -5.47 SIG 0.32 Yes
U S L 3 3 70.74 70.74 121.99 -57.92 592.68 0.58 0.75 NS 0.98 Yes
U S L 4 106 -42.02 -42.02 1.19 -13.98 -9.32 9.97 -7.50 SIG 0.00 No
U S LR 3 3 -8.02 -4.01 31.23 -41.79 107.29 -0.15 0.15 NS 0.46 Yes
U S LR 4 32 -30.94 -15.47 1.56 -8.74 -2.55 3.84 -3.17 SIG 0.65 Yes
U S R 3 2 -62.59 -62.59 15.45 -46.30 44.46 2.02 -1.19 NS 0.04 No
U S R 4 28 -25.74 -25.74 3.86 -16.67 -1.36 2.59 -2.23 SIG 0.04 No
U S XL 3 1 33.33 33.33 238.82 -96.02 4,362.97 0.14 0.16 n/a   n/a
U S XL 4 4 -4.97 -4.97 15.07 -25.62 36.40 0.19 -0.18 NS 0.08 Yes
U U L 3 10 -55.44 -55.44 17.53 -79.39 -3.65 3.16 -2.05 SIG 0.61 Yes
U U L 4 16 -69.37 -69.37 3.26 -39.91 -26.76 10.64 -5.56 SIG 0.59 Yes
U U LR 4 2 53.64 26.82 80.23 -40.08 545.03 0.33 0.41 NS 0.18 Yes
U U R 4 1 -69.49 -69.49 71.55 -99.69 2,924.77 0.97 -0.51 n/a   n/a

a Ratio of mean percent change in accident frequency to standard error of percent change in accident frequency per turn lane installed.

Table C-6. Yoked Comparison Evaluation Results for Fatal and Injury Accidents on Individual Intersection Approaches.
Area type Traffic control Project type No. of legs No. of improved sites Percent change in accident frequency Treatment effect Test for homogeneity
Mean Mean per added lane Standard error Lower 95% confidence limit Upper 95% confidence limit Ratioa Calculated Z Significant at 5% level? Calculated H probability Homogeneous at 5% level?
R N L 4 4 -78.75 -78.75 8.67 -47.85 2.62 4.54 -1.90 NS 0.65 Yes
R N LR 4 2 -24.25 -12.12 44.62 -46.24 331.17 0.27 -0.24 NS 0.50 Yes
R N R 4 2 32.74 32.74 48.91 -34.35 231.36 0.33 0.38 NS 0.80 Yes
R S XL 3 2 64.93 64.93 203.08 -85.24 1,742.63 0.32 0.41 NS 0.86 Yes
R S XL 4 4 21.37 21.37 78.62 -65.90 332.02 0.27 0.30 NS 1.00 Yes
R S XLR 4 2 21.91 10.96 24.06 -14.67 190.29 0.15 0.17 NS 0.51 Yes
R U L 3 34 -40.80 -40.80 22.53 -71.92 24.82 1.81 -1.38 NS 0.99 Yes
R U L 4 41 -54.97 -54.97 6.89 -39.60 -11.12 4.25 -2.77 SIG 1.00 Yes
R U LR 3 24 -28.23 -14.11 28.77 -58.50 73.32 0.78 -0.66 NS 1.00 Yes
R U LR 4 29 -6.43 -3.22 15.69 -25.76 40.29 0.20 -0.20 NS 1.00 Yes
R U R 3 11 26.71 26.71 86.25 -66.62 381.08 0.31 0.35 NS 0.99 Yes
R U R 4 43 -10.90 -10.90 15.76 -29.77 35.65 0.41 -0.38 NS 1.00 Yes
R U XL 4 2 121.96 121.96 319.21 -86.75 3,619.01 0.38 0.55 NS 0.30 Yes
U N L 3 6 -38.23 -38.23 24.38 -49.79 74.56 0.94 -0.73 NS 0.80 Yes
U N L 4 49 -58.14 -58.14 4.99 -37.53 -17.26 5.94 -3.73 SIG 1.00 Yes
U S L 3 3 210.12 210.12 284.05 -48.49 1,767.16 0.74 1.24 NS 0.94 Yes
U S L 4 114 -39.99 -39.99 1.93 -14.58 -6.97 5.81 -4.46 SIG 0.81 Yes
U S LR 3 4 55.16 27.58 74.90 -41.65 360.97 0.49 0.61 NS 0.88 Yes
U S LR 4 34 -34.35 -17.17 2.62 -10.95 -0.39 2.56 -2.06 SIG 0.92 Yes
U S R 3 2 -86.69 -86.69 9.25 -49.56 51.49 4.69 -1.45 NS 0.78 Yes
U S R 4 30 -29.85 -29.85 6.36 -21.30 4.57 1.78 -1.48 NS 0.98 Yes
U S XL 3 1 -28.57 -28.57 148.85 -98.80 4,143.93 0.19 -0.16 n/a   n/a
U S XL 4 4 -53.37 -53.37 14.86 -48.21 22.37 2.05 -1.37 NS 0.30 Yes
U U L 3 10 -52.96 -52.96 26.42 -84.35 41.44 2.00 -1.34 NS 0.84 Yes
U U L 4 16 -77.79 -77.79 3.70 -44.22 -28.66 10.51 -4.52 SIG 0.90 Yes
U U LR 4 2 -62.87 -31.43 29.45 -49.17 365.89 1.07 -0.62 NS 0.58 Yes
U U R 4 1 -38.98 -38.98 149.46 -99.50 7,321.45 0.26 -0.20 n/a   n/a

a Ratio of mean percent change in accident frequency to standard error of percent change in accident frequency per turn lane installed.

Table C-7. Yoked Comparison Evaluation Results for Project-Related Accidents on Individual Intersection Approaches.
Area type Traffic control Project type No. of legs No. of improved sites Percent change in accident frequency Treatment effect Test for homogeneity
Mean Mean per added lane Standard error Lower 95% confidence limit Upper 95% confidence limit Ratioa Calculated Z Significant at 5% level? Calculated H probability Homogeneous at 5% level?
R N L 4 4 -29.35 -29.35 40.58 -46.28 285.61 0.36 -0.30 NS 0.85 Yes
R N LR 4 2 -28.14 -14.07 69.42 -49.19 1,535.50 0.20 -0.17 NS 0.87 Yes
R N R 4 2 0.01 0.01 100.01 -49.01 2,470.19 0.00 0.00 NS 1.00 Yes
R S XL 3 2 -12.07 -12.07 175.87 -98.26 4,331.89 0.07 -0.06 NS 0.96 Yes
R S XL 4 4 15.21 15.21 111.82 -82.81 672.11 0.14 0.15 NS 0.98 Yes
R S XLR 4 2 14.57 7.29 32.12 -15.96 499.57 0.08 0.08 NS 0.67 Yes
R U L 3 34 2.03 2.03 49.49 -60.57 164.00 0.04 0.04 NS 1.00 Yes
R U L 4 41 -25.66 -25.66 15.50 -34.87 32.03 0.88 -0.76 NS 1.00 Yes
R U LR 3 24 -10.95 -5.48 40.46 -56.60 136.84 0.22 -0.20 NS 1.00 Yes
R U LR 4 30 19.17 9.58 26.34 -24.94 91.70 0.36 0.40 NS 1.00 Yes
R U R 3 11 5.84 5.84 90.26 -80.11 463.06 0.06 0.07 NS 1.00 Yes
R U R 4 43 -9.68 9.68 21.27 -34.60 57.55 0.27 -0.25 NS 1.00 Yes
R U XL 4 2 30.05 30.05 209.71 -94.48 2,966.70 0.14 0.16 NS 0.57 Yes
U N L 3 6 -21.71 -21.71 51.73 -54.57 346.63 0.25 -0.22 NS 1.00 Yes
U N L 4 50 -8.21 -8.21 15.32 -26.36 37.90 0.27 -0.26 NS 1.00 Yes
U S L 3 3 -0.44 -0.44 162.58 -95.94 2,344.12 0.00 -0.00 NS 0.99 Yes
U S L 4 115 -33.88 33.88 2.87 -14.34 2.90 3.30 -2.66 SIG 1.00 Yes
U S LR 3 5 95.11 47.55 140.81 -49.82 1,109.84 0.42 0.58 NS 0.99 Yes
U S LR 4 32 -59.67 -29.83 1.77 -14.68 7.51 6.69 -4.10 SIG 0.79 Yes
U S R 3 2 -41.79 -41.79 47.53 -48.81 664.46 0.44 -0.33 NS 0.88 Yes
U S R 4 34 66.04 66.04 15.90 1.30 66.00 1.64 2.09 SIG 0.01 No
U S XL 3 1 0.00 0.00 282.84 -99.61 25,462.64 0.00 0.00 n/a   n/a
U S XL 4 5 108.84 108.84 113.24 -38.42 730.24 0.53 0.75 NS 0.71 Yes
U U L 3 10 14.06 14.06 101.30 -79.99 550.30 0.14 0.15 NS 1.00 Yes
U U L 4 16 -78.11 -78.11 5.15 -45.65 22.50 7.59 -3.23 SIG 0.97 Yes
U U LR 4 2 141.99 70.99 169.28 -42.21 1,828.13 0.42 0.63 NS 0.65 Yes
U U R 4 1 -38.98 -38.98 172.58 -99.76 15,497.21 0.23 -0.17 n/a   n/a

a Ratio of mean percent change in accident frequency to standard error of percent change in accident frequency per turn lane installed.

 

Table C-8. Yoked Comparison Evaluation Results for Project-Related Fatal and Injury Accidents on Individual Intersection Approaches.
Area type Traffic control Project type No. of legs No. of improved sites Percent change in accident frequency Treatment effect Test for homogeneity
Mean Mean per added lane Standard error Lower 95% confidence limit Upper 95% confidence limit Ratioa Calculated Z Significant at 5% level? Calculated H probability Homogeneous at 5% level?
R N L 4 4 -15.07 -15.07 52.96 -46.32 439.40 0.14 -0.13 NS 1.00 Yes
R N LR 4 2 -28.14 -14.07 69.42 -49.19 1,535.50 0.20 -0.17 NS 0.87 Yes
R N R 4 2 0.01 0.01 100.01 -49.01 2,470.19 0.00 0.00 NS 1.00 Yes
R S XL 3 2 -12.07 -12.07 175.87 -98.26 4,331.89 0.07 -0.06 NS 0.96 Yes
R S XL 4 4 163.58 163.58 295.30 -70.67 2,268.98 0.55 0.87 NS 0.86 Yes
R S XLR 4 2 29.41 14.70 37.44 -15.95 631.00 0.13 0.15 NS 0.90 Yes
R U L 3 34 2.03 2.03 49.49 -60.57 164.00 0.04 0.04 NS 1.00 Yes
R U L 4 41 -23.73 -23.73 16.79 -35.19 38.08 0.75 -0.66 NS 1.00 Yes
R U LR 3 24 -11.66 -5.83 40.56 -57.05 137.67 0.23 -0.22 NS 1.00 Yes
R U LR 4 30 -2.49 -1.25 23.43 -30.99 75.04 0.05 -0.05 NS 1.00 Yes
R U R 3 11 5.84 5.84 90.26 -80.11 463.06 0.06 0.07 NS 1.00 Yes
R U R 4 43 -5.70 -5.70 23.30 -34.49 67.48 0.14 -0.14 NS 1.00 Yes
R U XL 4 2 110.86 110.86 390.43 -94.40 7,845.84 0.28 0.40 NS 0.73 Yes
U N L 3 6 2.78 2.78 71.21 -53.59 532.89 0.02 0.02 NS 1.00 Yes
U N L 4 50 -16.09 -16.09 15.63 -30.09 36.55 0.53 -0.48 NS 1.00 Yes
U S L 3 3 -0.44 -0.44 162.58 -95.94 2,344.12 0.00 0.00 NS 0.99 Yes
U S L 4 116 -2.23 -2.23 5.62 -9.66 13.00 0.11 -0.11 NS 1.00 Yes
U S LR 3 5 -3.01 -1.51 75.60 -57.24 636.13 0.02 -0.02 NS 1.00 Yes
U S LR 4 33 -50.96 -25.48 3.37 -14.93 0.69 3.01 -2.06 SIG 1.00 Yes
U S R 3 2 -10.24 -10.24 89.76 -49.11 2,211.92 0.06 -0.05 NS 0.97 Yes
U S R 4 35 62.30 62.30 21.67 -6.69 84.83 1.12 1.41 NS 0.96 Yes
U S XL 3 1 0.00 0.00 282.84 -99.61 25,462.64 0.00 0.00 n/a   n/a
U S XL 4 5 29.49 29.49 80.25 -47.48 584.96 0.20 0.23 NS 0.99 Yes
U U L 3 10 5.30 5.30 94.18 -81.76 507.82 0.06 0.06 NS 1.00 Yes
U U L 4 16 -68.60 -68.60 8.60 -44.63 4.08 3.99 -2.12 SIG 1.00 Yes
U U LR 4 2 -27.38 -13.69 70.16 -49.18 1,552.27 0.20 -0.17 NS 0.86 Yes
U U R 4 1 -38.98 -38.98 172.58 -99.76 15,497.21 0.23 -0.17 n/a   n/a

a Ratio of mean percent change in accident frequency to standard error of percent change in accident frequency per turn lane installed.

ss
Table C-9. Yoked Comparison Evaluation for Project-Related Intersection Accidents—Auto Matched.
Area type Traffic control Project type No. of legs No. of improved sites Percent change in accident frequency Treatment effect Test for homogeneity
Mean Mean per added lane Standard error Lower 95% confidence limit Upper 95% confidence limit Ratioa Calculated Z Significant at 5% level? Calculated H probability Homogeneous at 5% level?
R N L 4 2 109.08 54.54 104.11 -35.16 686.24 0.52 0.74 NS 0.99 Yes
R N LR 4 1 283.33 141.67 393.27 -46.56 10,643.71 0.36 0.65 n/a   n/a
R N R 4 1 -38.64 -19.32 61.82 -49.41 1,542.16 0.31 -0.24 n/a   n/a
R S XL 3 2 350.52 350.52 705.43 -79.07 9,595.30 0.50 0.96 NS 0.94 Yes
R S XL 4 4 7.61 7.61 82.50 -76.06 383.60 0.09 0.10 NS 0.91 Yes
R S XLR 4 1 -9.38 -2.34 36.95 -24.07 528.79 0.06 -0.06 n/a   n/a
R U L 3 34 123.68 123.68 83.83 7.30 366.29 1.48 2.15 SIG 1.00 Yes
R U L 4 22 3.70 2.09 20.20 -26.68 58.70 0.10 0.11 NS 0.90 Yes
R U LR 3 12 120.86 96.69 118.15 -32.36 575.28 0.82 1.18 NS 0.98 Yes
R U LR 4 15 66.35 33.17 30.01 -9.00 118.72 1.11 1.41 NS 1.00 Yes
R U R 3 11 7.02 7.02 75.92 -73.36 329.86 0.09 0.10 NS 1.00 Yes
R U R 4 28 27.10 17.64 30.75 -25.16 106.30 0.57 0.65 NS 1.00 Yes
R U XL 4 2 89.07 89.07 190.91 -73.87 1,268.04 0.47 0.63 NS 0.22 Yes
U N L 3 4 33.86 22.57 89.80 -54.25 574.73 0.25 0.29 NS 0.81 Yes
U N L 4 24 92.22 48.12 23.77 10.85 107.42 2.02 2.76 SIG 0.41 Yes
U S L 3 3 72.16 72.16 220.51 -86.02 2,019.53 0.33 0.42 NS 0.64 Yes
U S L 4 37 -0.32 -0.10 3.88 -6.86 8.50 0.03 -0.03 NS 0.05 Yes
U S LR 3 2 21.81 14.54 107.34 -60.58 1,016.60 0.14 0.15 NS 0.64 Yes
U S LR 4 9 -44.51 -11.45 2.30 -15.31 6.15 4.98 -3.66 SIG 0.28 Yes
U S R 3 1 237.50 118.75 181.91 -29.60 1,345.85 0.65 1.13 n/a   n/a
U S R 4 12 2.36 1.23 8.42 -12.97 20.58 0.15 0.15 NS 0.02 No
U S XL 3 1 100.00 100.00 406.20 -96.27 10,611.75 0.25 0.34 n/a   n/a
U S XL 4 3 -31.92 -19.15 21.37 -45.35 53.87 0.90 -0.73 NS 0.78 Yes
U U L 3 10 202.64 202.64 213.44 -24.04 1,105.75 0.95 1.57