Assessing the Impact of 20 mph Speed Limits on Vehicle Speeds in Rural Areas: The Case of the Scottish Borders
Abstract
:1. Introduction
1.1. Background, Aim and Contributions of the Study
1.2. Previous Research on the Effectiveness of Lower Speed Limits
1.2.1. Lower Speed Limits and Vehicle Speeds
1.2.2. 20 mph Speed Limit, Public Health and Well-Being
1.2.3. Implementation of the 20 mph Speed Limit in Urban Areas
1.2.4. 20 mph Speed Limit in Rural Areas and Evidence Gap
2. Materials and Methods
2.1. Overview of the Intervention and Evaluation Process
- Survey 1: carried out before the introduction of the 20 mph speed limit, i.e., between August and September 2020 (also referred to as “before”).
- Survey 2: carried out immediately after (4 or 5 weeks for most of the sites) the establishment of the 20 mph speed limit (also referred to as “After I”).
- Survey 3: carried out several months (5 to 6 months for most of the sites) after the establishment of the 20 mph speed limit (also referred to as “After II”).
- Survey 4: carried out several months (7 to 8 months for most of the sites) after the establishment of the 20 mph speed limit (also referred to as “After III”).
2.2. Data Collection and Processing
2.3. Speed Metrics
- (i)
- An enforcement-based threshold that was set in the past by the former Association of Chief Police Officers (ACPO) in the UK (currently the National Police Chiefs’ Council—NPCC) as a typical tolerance for speed enforcement. This threshold is defined as the speed limit increased by 10% plus 2 mph (i.e., 1.1 × speed limit + 2 mph). For instance, on 20 mph speed limit roads, this speed threshold stands at 24 mph. Such a speed metric can provide useful insights into the extent of drivers’ compliance and observed speeding patterns after the onset of a 20 mph speed limit intervention. This speed value is hereafter referred to as the “ACPO threshold”.
- (ii)
- An excessive speeding threshold, which was suggested by the Department for Transport (DfT) in the UK; this is equal to the speed limit plus 15 mph. For instance, on a road with a 20 mph speed limit, the DfT threshold is equal to 35 mph. This threshold serves as a key metric in official reports and intends to capture the extent of extreme violations of the speed limit. This speed value is hereafter referred to as the “DfT threshold”.
2.4. Statistical Analysis
3. Results and Discussion
3.1. Before–after Analysis of Mean and 85th Percentile Speeds
3.1.1. Group 1: Sites with Mean Speed Less Than or Equal to 20 mph “Before”
3.1.2. Group 2: Sites with Mean Speed Greater Than 20 mph “Before”
3.1.3. Evolution of Speed over Time
3.1.4. Percentage of Vehicles with Speed over PSL, ACPO and DfT
3.2. Statistical Analysis of Vehicle Speeds
3.2.1. Wilcoxon Signed-Rank Tests
3.2.2. Paired Sample t-Tests
3.2.3. Linear Regression Analysis of Vehicle Speeds
4. Policy Implications and Conclusions
4.1. Summary of Findings
4.2. Policy Implications and Future Work
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
Appendix A
Site No | Site Name | No. of Observations (n) | Mean | SD | SE | t-Stat | p-Value | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
before | after I | after III | before | after I | after III | before | after I | after III | before | after I | after III | B-AI | B-AIII | B-AI | B-AIII | ||
1 | Broughton | 11,848 | 7416 | 12,538 | 29.8 | 26.87 | 26.06 | 5.99 | 7.13 | 6.33 | 0.0551 | 0.0828 | 0.0566 | 29.45 | 47.39 | 0 | 0 |
3 | A703 | 45,549 | 36,320 | 48,508 | 29.71 | 24.82 | 24.55 | 4.27 | 5.11 | 5.12 | 0.02 | 0.0268 | 0.0232 | 146.22 | 168.27 | 0 | 0 |
4 | Eddleston (Central) | 45,074 | 36,599 | 48,159 | 26.94 | 22.64 | 22.52 | 4.33 | 3.89 | 3.94 | 0.0204 | 0.0204 | 0.018 | 149.29 | 162.93 | 0 | 0 |
5 | A703 | 44,856 | 36,530 | 48,597 | 30.4 | 24.31 | 25.48 | 5.14 | 5.03 | 5.64 | 0.0243 | 0.0263 | 0.0256 | 170.13 | 139.58 | 0 | 0 |
6 | A72 Pirn Road, Innerleithen | 42,383 | 37,072 | 44,710 | 24.58 | 20.86 | 21.62 | 6.71 | 5.53 | 5.71 | 0.0326 | 0.0287 | 0.027 | 85.62 | 69.8 | 0 | 0 |
7 | B709 Leithen Road | 8173 | 6183 | 9902 | 24.47 | 23.66 | 22.51 | 5.39 | 5.43 | 5.67 | 0.0597 | 0.0691 | 0.0569 | 8.91 | 23.82 | 0 | 0 |
8 | B7062 Kingsmeadow Road | 11,431 | 10,468 | 12,512 | 30.72 | 25.29 | 26.01 | 6.76 | 5.74 | 6.26 | 0.0632 | 0.0561 | 0.056 | 64.31 | 55.84 | 0 | 0 |
9 | A703 Edinburgh Road | 53,626 | 40,293 | 57,648 | 25.29 | 22.9 | 23.44 | 4.62 | 4.38 | 4.56 | 0.0199 | 0.0218 | 0.019 | 80.65 | 66.95 | 0 | 0 |
11 | A72 Neidpath | 28,358 | 21,290 | 32,337 | 27.4 | 22.99 | 22.97 | 6.7 | 5.87 | 5.69 | 0.0398 | 0.0402 | 0.0316 | 78.05 | 87.15 | 0 | 0 |
12 | A701 | 14,173 | 10,520 | 16,744 | 40.75 | 30.7 | 30.45 | 6.56 | 8.44 | 8.28 | 0.0551 | 0.0823 | 0.064 | 101.46 | 121.91 | 0 | 0 |
13 | A72 | 8570 | 6420 | 9468 | 32.69 | 27.47 | 27.05 | 5.15 | 5.75 | 5.53 | 0.0556 | 0.0718 | 0.0569 | 57.46 | 70.89 | 0 | 0 |
14 | A72 Peebles Road | 29,655 | 29,655 | 37,957 | 29.21 | 24.4 | 25.49 | 4.27 | 4.74 | 5.03 | 0.0248 | 0.0275 | 0.0258 | 129.66 | 103.73 | 0 | 0 |
16 | B6461 Duns Road | 1000 | 1000 | 13,476 | 30.11 | 26.09 | 27.11 | 5.79 | 6.28 | 6.79 | 0.183 | 0.1987 | 0.0585 | 14.89 | 46.79 | 0 | 0 |
17 | B6400 | 3533 | 2994 | 3877 | 27.59 | 25.01 | 24 | 5.93 | 5.34 | 5.54 | 0.0997 | 0.0976 | 0.089 | 18.44 | 26.86 | 0 | 0 |
18 | A698 Main Street | 18,380 | 12,743 | 18,521 | 28.57 | 21.92 | 23.78 | 4.58 | 4.16 | 4.33 | 0.0338 | 0.0368 | 0.0318 | 132.99 | 103.14 | 0 | 0 |
19 | Main Street | 2656 | 2491 | 2663 | 28.09 | 23.97 | 24.12 | 5.94 | 5.36 | 5.85 | 0.1153 | 0.1074 | 0.1133 | 26.14 | 24.53 | 0 | 0 |
20 | A698 Main Street | 28,936 | 23,068 | 30,702 | 29.89 | 23.32 | 23.98 | 4.79 | 4.86 | 4.97 | 0.0282 | 0.032 | 0.0284 | 153.93 | 147.61 | 0 | 0 |
21 | Oxnam Rd | 16,783 | 12,598 | 17,042 | 28.95 | 24.97 | 25.45 | 4.56 | 4.18 | 4.42 | 0.0352 | 0.0373 | 0.0339 | 77.69 | 71.68 | 0 | 0 |
23 | A699 Main Street | 15,392 | 11,849 | 15,662 | 30.52 | 24.32 | 25.18 | 5.08 | 5.35 | 5.55 | 0.041 | 0.0491 | 0.0443 | 96.86 | 88.51 | 0 | 0 |
24 | B6401 Main Street | 4319 | 3558 | 3903 | 25.25 | 21.58 | 21.86 | 5.99 | 5.4 | 5.46 | 0.0912 | 0.0906 | 0.0874 | 28.49 | 26.8 | 0 | 0 |
25 | Unnamed road | 1909 | 1417 | 1767 | 23.01 | 21.32 | 21.26 | 6.04 | 4.85 | 5.39 | 0.1384 | 0.1289 | 0.1283 | 8.91 | 9.26 | 0 | 0 |
26 | Unnamed road | 566 | 387 | 892 | 17.89 | 17.14 | 16.78 | 4.47 | 4.07 | 4.25 | 0.1879 | 0.2068 | 0.1422 | 2.7 | 4.69 | 0.01 | 0 |
27 | C78, Smailholm | 8003 | 6815 | 8063 | 32.24 | 26.67 | 27.94 | 6.48 | 6.33 | 6.66 | 0.0725 | 0.0766 | 0.0742 | 52.82 | 41.5 | 0 | 0 |
28 | B6350 | 12,611 | 7428 | 36.64 | 33.18 | 5.5 | 5.73 | 0.049 | 0.0665 | 41.83 | 0 | ||||||
31 | B6364 Main Street | 7904 | 6921 | 8809 | 29.55 | 25.67 | 26.27 | 4.92 | 4.91 | 4.98 | 0.0553 | 0.059 | 0.0531 | 48.01 | 42.87 | 0 | 0 |
32 | B6401 Cheviot Place | 4315 | 3432 | 4311 | 28.48 | 25.26 | 25.87 | 6.47 | 6.24 | 6.76 | 0.0985 | 0.1065 | 0.1029 | 22.21 | 18.28 | 0 | 0 |
33 | Unnamed road | 768 | 637 | 744 | 21.01 | 20.56 | 18.91 | 6.55 | 5.59 | 5.32 | 0.2365 | 0.2213 | 0.1951 | 1.42 | 6.86 | 0.16 | 0 |
34 | Unnamed road, Ashkirk | 3389 | 2704 | 4018 | 20.05 | 19.15 | 19.44 | 3.87 | 3.53 | 3.89 | 0.0665 | 0.0679 | 0.0613 | 9.49 | 6.72 | 0 | 0 |
36 | A72 Vine Street | 32,303 | 28,739 | 32,411 | 27.88 | 23.08 | 23.33 | 3.66 | 4.02 | 4.13 | 0.0204 | 0.0237 | 0.0229 | 153.41 | 148.28 | 0 | 0 |
37 | B6394 Main Street | 9163 | 8053 | 7783 | 15.64 | 14.24 | 13.52 | 3.08 | 2.96 | 2.69 | 0.0322 | 0.033 | 0.0305 | 30.39 | 47.76 | 0 | 0 |
38 | A6105 | 23,364 | 14,769 | 22,858 | 29.58 | 25.51 | 23.24 | 5.18 | 4.82 | 5.16 | 0.0339 | 0.0396 | 0.0341 | 78.01 | 131.76 | 0 | 0 |
39 | Main Street, Ettrickbridge | 2922 | 2194 | 3145 | 23.03 | 21.86 | 20.35 | 5.74 | 5.2 | 4.97 | 0.1061 | 0.1111 | 0.0886 | 7.63 | 19.34 | 0 | 0 |
40 | Old Stage Road | 1065 | 829 | 1178 | 21.36 | 19.93 | 18.36 | 6.88 | 6.28 | 5.75 | 0.2109 | 0.2179 | 0.1676 | 4.72 | 11.17 | 0 | 0 |
41 | B6374 Melrose Road, Galashiels | 53,315 | 52,001 | 50,478 | 29.62 | 23.11 | 24.45 | 4.56 | 3.91 | 4.09 | 0.0198 | 0.0171 | 0.0182 | 248.66 | 192.23 | 0 | 0 |
42 | Scott Street | 42,612 | 42,612 | 47,150 | 23.73 | 20.93 | 22.91 | 4.77 | 4 | 4.29 | 0.0231 | 0.0194 | 0.0197 | 92.94 | 27.04 | 0 | 0 |
43 | A7 Abbotsford Road | 128,740 | 115,609 | 125,388 | 27.16 | 21.09 | 22.72 | 4.27 | 3.76 | 3.92 | 0.0119 | 0.0111 | 0.0111 | 373.67 | 273.19 | 0 | 0 |
44 | Windyknowe Road, Galashiels | 11,978 | 11,978 | 14,258 | 25.86 | 22.38 | 23.19 | 4.53 | 3.93 | 4.29 | 0.0414 | 0.0359 | 0.0359 | 63.48 | 48.7 | 0 | 0 |
45 | B6360 Main St, Gattonside | 17,177 | 14,875 | 16,202 | 29.78 | 23.86 | 24.55 | 4.89 | 4.68 | 4.94 | 0.0373 | 0.0384 | 0.0388 | 110.68 | 97.15 | 0 | 0 |
46 | Shoestanes Rd, Heriot | 749 | 662 | 1230 | 15.12 | 15.45 | 25.99 | 4.3 | 4.13 | 7.39 | 0.157 | 0.1604 | 0.2107 | −1.48 | −41.41 | 0.14 | 0 |
47 | Thirlestane Dr, Lauder | 3667 | 2592 | 4566 | 16.87 | 14.56 | 14.89 | 3.17 | 3.04 | 3.11 | 0.0523 | 0.0598 | 0.0461 | 29.1 | 28.41 | 0 | 0 |
48 | B6362 Stow Rd, Lauder | 13,547 | 3757 | 6378 | 34.77 | 26.48 | 28.27 | 9.37 | 6.37 | 6.62 | 0.0805 | 0.1038 | 0.0828 | 63.07 | 56.29 | 0 | 0 |
49 | B6359 Main St, Lilliesleaf | 3631 | 3631 | 4308 | 20.59 | 19.45 | 19.99 | 5.72 | 4.62 | 5 | 0.095 | 0.0766 | 0.0762 | 9.35 | 4.9 | 0 | 0 |
52 | Main Street, Midlem | 3551 | 3059 | 3081 | 23.5 | 21.75 | 23.03 | 6.08 | 5.36 | 5.18 | 0.102 | 0.097 | 0.0934 | 12.41 | 3.43 | 0 | 0.001 |
53 | B6361 Main Street, Newstead | 4163 | 3459 | 4518 | 21.78 | 20.66 | 20.31 | 4.75 | 4.18 | 4.28 | 0.0736 | 0.0711 | 0.0637 | 10.88 | 15.09 | 0 | 0 |
55 | Station Road, Oxton | 3392 | 3392 | 4118 | 22.25 | 20.68 | 19.49 | 5.44 | 4.77 | 5.21 | 0.0934 | 0.0819 | 0.0813 | 12.64 | 22.26 | 0 | 0 |
56 | Unnamed road | 862 | 862 | 989 | 15.15 | 14.84 | 15.13 | 3.49 | 3.49 | 3.45 | 0.1189 | 0.1188 | 0.1098 | 1.83 | 0.21 | 0.067 | 0.845 |
57 | A707 Linglie Road, Selkirk | 9723 | 5334 | 10,399 | 35.72 | 32.95 | 32.33 | 7.05 | 7.15 | 6.79 | 0.0715 | 0.0979 | 0.0666 | 22.82 | 34.67 | 0 | 0 |
59 | Bleachfield Road, Selkirk | 15,070 | 11,268 | 17,155 | 24.74 | 22.49 | 23.33 | 5.04 | 4.43 | 4.7 | 0.0411 | 0.0418 | 0.0359 | 38.51 | 25.82 | 0 | 0 |
60 | A7 Galashiels Road | 56,061 | 24,090 | 31,034 | 29.62 | 23.88 | 23.54 | 3.88 | 4.59 | 4.56 | 0.0164 | 0.0296 | 0.0259 | 169.74 | 198.69 | 0 | 0 |
61 | A7, Stow (North) | 53,513 | 22,561 | 29,095 | 26.77 | 23.5 | 23.5 | 4.41 | 4.57 | 4.57 | 0.0191 | 0.0304 | 0.0268 | 91.09 | 99.51 | 0 | 0 |
64 | A6088, Chesters | 4736 | 2945 | 5496 | 22.93 | 21.47 | 21.28 | 3.96 | 4.24 | 3.83 | 0.0575 | 0.0782 | 0.0517 | 15 | 21.38 | 0 | 0 |
65 | A698 Jedburgh Road, Denholm | 28,552 | 26,541 | 32,163 | 28.72 | 23.83 | 24.33 | 5.4 | 5.47 | 5.81 | 0.032 | 0.0336 | 0.0324 | 105.38 | 96.43 | 0 | 0 |
67 | B6399 Liddesdale Road, Hawick | 11,828 | 8722 | 11,879 | 25.53 | 23.11 | 23.07 | 5.03 | 4.87 | 4.93 | 0.0462 | 0.0521 | 0.0452 | 34.74 | 38.09 | 0 | 0 |
69 | B6357 North Hermitage Street | 5836 | 3882 | 6744 | 29.11 | 22.77 | 27.58 | 5.51 | 5.6 | 5.78 | 0.0721 | 0.0898 | 0.0704 | 55.1 | 15.21 | 0 | 0 |
70 | B6437 Main St, Allanton | 8520 | 7194 | 8900 | 29.26 | 22.42 | 24.32 | 4.99 | 5.1 | 5.72 | 0.0541 | 0.0601 | 0.0606 | 84.61 | 60.87 | 0 | 0 |
71 | B6355, Ayton | 10,018 | 8653 | 11,267 | 25.75 | 21.78 | 22.45 | 5.01 | 4.29 | 4.53 | 0.0501 | 0.0461 | 0.0427 | 58.32 | 50.21 | 0 | 0 |
72 | Unnamed rd., Burnmouth | 5650 | 3226 | 6592 | 27.54 | 24.44 | 25.51 | 5.15 | 5.38 | 5.55 | 0.0686 | 0.0947 | 0.0683 | 26.54 | 20.96 | 0 | 0 |
73 | Crosshill/Kirkgate, Chirnside | 5929 | 5268 | 6200 | 18.38 | 17.5 | 18.64 | 3.16 | 2.95 | 3.13 | 0.0411 | 0.0406 | 0.0398 | 15.25 | −4.44 | 0 | 0 |
74 | Hoprig Rd /The Square | 3044 | 2940 | 3537 | 19.01 | 19.91 | 19.54 | 4.1 | 4.25 | 4.25 | 0.0743 | 0.0783 | 0.0715 | −8.37 | −5.17 | 0 | 0 |
76 | Duns Road, Coldsteam | 9108 | 7940 | 9066 | 28.11 | 22.76 | 22.8 | 5.36 | 4.93 | 5.36 | 0.0561 | 0.0553 | 0.0563 | 67.81 | 66.77 | 0 | 0 |
77 | Unnamed road, Cove | 2173 | 754 | 2069 | 14.47 | 15.18 | 14.13 | 3.64 | 3.86 | 3.52 | 0.078 | 0.1405 | 0.0774 | −4.37 | 3.12 | 0 | 0.002 |
78 | A6105 Langtongate, Duns | 28,455 | 26,039 | 31,635 | 28.82 | 22.82 | 23.87 | 6.04 | 4.78 | 5.09 | 0.0358 | 0.0296 | 0.0286 | 129.23 | 108.13 | 0 | 0 |
79 | B6461 Main Street, Eccles | 10,873 | 10,029 | 31 | 24.31 | 6.16 | 5.33 | 0.0591 | 0.0532 | 84.19 | 0 | ||||||
80 | A1107, Eyemouth | 23,653 | 15,069 | 23,742 | 28.54 | 23.74 | 23.35 | 4.29 | 4.25 | 4.69 | 0.0279 | 0.0346 | 0.0304 | 107.94 | 125.64 | 0 | 0 |
81 | Unnamed road, Foulden | 1331 | 1331 | 1479 | 23.35 | 22.64 | 23.91 | 6.97 | 5.78 | 5.9 | 0.191 | 0.1586 | 0.1534 | 2.85 | −2.31 | 0.004 | 0.021 |
82 | A6105, Foulden | 18,045 | 13,493 | 18,139 | 37.36 | 31.85 | 36.89 | 5.26 | 5.78 | 5.27 | 0.0392 | 0.0497 | 0.0392 | 87.04 | 8.48 | 0 | 0 |
83 | Main Street, Gavinton | 2153 | 2153 | 3153 | 28.59 | 23.71 | 22.75 | 5.43 | 5.22 | 5.76 | 0.1169 | 0.1125 | 0.1027 | 30.04 | 37.48 | 0 | 0 |
84 | Bankhouse, Grantshouse | 581 | 553 | 613 | 18.82 | 18.91 | 19.28 | 5.25 | 5.28 | 5.33 | 0.2176 | 0.2246 | 0.2154 | −0.3 | −1.5 | 0.764 | 0.133 |
85 | Duns Road between Queens Row and The Avenue Greenlaw | 17,091 | 16,998 | 9100 | 29.95 | 24.87 | 27.8 | 5.47 | 5.21 | 5.72 | 0.0418 | 0.0399 | 0.06 | 87.87 | 29.48 | 0 | 0 |
86 | B6461 Main Street | 9770 | 7936 | 9933 | 26.79 | 22.29 | 23.38 | 5.44 | 4.55 | 4.9 | 0.055 | 0.051 | 0.0492 | 59.99 | 46.16 | 0 | 0 |
87 | A6112, Lennel | 4911 | 3557 | 5043 | 28.75 | 23.4 | 24.64 | 5.84 | 5.65 | 6.39 | 0.0833 | 0.0947 | 0.09 | 42.38 | 33.53 | 0 | 0 |
88 | Gifford Road, Longformacus | 2052 | 1317 | 1753 | 18.64 | 17.77 | 18.49 | 3.58 | 3.3 | 3.61 | 0.0791 | 0.0908 | 0.0861 | 7.3 | 1.33 | 0 | 0.183 |
90 | A6112, Preston | 15,093 | 11,264 | 13,451 | 30.05 | 24.5 | 25.14 | 5.11 | 4.96 | 5.16 | 0.0416 | 0.0467 | 0.0445 | 88.82 | 80.64 | 0 | 0 |
91 | B6438 Main St, Reston | 4638 | 3609 | 5239 | 27.34 | 24.2 | 24.7 | 4.51 | 4.54 | 4.66 | 0.0662 | 0.0756 | 0.0644 | 31.23 | 28.59 | 0 | 0 |
92 | B6438, St Abbs | 7656 | 3073 | 7561 | 20.03 | 20.48 | 19.62 | 4.74 | 4.64 | 4.25 | 0.0542 | 0.0837 | 0.0488 | −4.44 | 5.7 | 0 | 0 |
93 | A6112, Main St, Swinton | 9670 | 7635 | 9324 | 24.97 | 22.53 | 23.96 | 4.68 | 4.11 | 4.62 | 0.0475 | 0.047 | 0.0478 | 36.46 | 14.96 | 0 | 0 |
94 | B6456, Westruther | 2911 | 2911 | 4691 | 26.15 | 22.81 | 23.87 | 5.44 | 5.3 | 5.25 | 0.1008 | 0.0982 | 0.0767 | 23.7 | 17.93 | 0 | 0 |
105 | South Parks | 6550 | 6304 | 9034 | 22.63 | 20.8 | 19.33 | 4.73 | 4.26 | 4 | 0.0584 | 0.0536 | 0.0421 | 23.06 | 45.72 | 0 | 0 |
106 | Traquair | 4463 | 3248 | 6463 | 29.02 | 26.34 | 26.47 | 7.34 | 7.35 | 6.84 | 0.1099 | 0.129 | 0.0851 | 15.84 | 18.31 | 0 | 0 |
107 | Kirkhouse (near Traquair) | 3052 | 2350 | 5312 | 25.27 | 25 | 24.15 | 6.33 | 6 | 5.95 | 0.1145 | 0.1237 | 0.0817 | 1.59 | 7.96 | 0.112 | 0 |
108 | Minto | 1897 | 1814 | 842 | 23.3 | 22.17 | 22.51 | 5.43 | 5.07 | 4.95 | 0.1246 | 0.1191 | 0.1706 | 6.56 | 3.71 | 0 | 0 |
109 | Yarrowford | 793 | 793 | 831 | 18.63 | 18.85 | 15.82 | 4.23 | 4.39 | 4.48 | 0.1503 | 0.1558 | 0.1554 | −1.01 | 12.96 | 0.311 | 0 |
111 | Cotgreen Road | 3522 | 3522 | 3892 | 19.06 | 17.29 | 18.32 | 3.78 | 3.45 | 3.78 | 0.0637 | 0.0582 | 0.0605 | 20.49 | 8.35 | 0 | 0 |
112 | Oxnam | 2178 | 2178 | 2764 | 28.03 | 25.08 | 24.52 | 5.85 | 5.86 | 5.62 | 0.1254 | 0.1255 | 0.1068 | 16.62 | 21.31 | 0 | 0 |
114 | Unnamed road, Lanton | 1092 | 985 | 1390 | 18.68 | 18.2 | 16.96 | 3.69 | 3.96 | 3.81 | 0.1117 | 0.1263 | 0.1022 | 2.85 | 11.37 | 0.005 | 0 |
115 | B6356, Clintmains | 2463 | 1327 | 3111 | 28.11 | 21.75 | 21.63 | 5.23 | 4.35 | 4.86 | 0.1054 | 0.1195 | 0.0871 | 39.91 | 47.38 | 0 | 0 |
116 | B6356, Bemersyde | 1517 | 839 | 2094 | 20.97 | 19.85 | 20.37 | 5.12 | 4.88 | 5.12 | 0.1315 | 0.1686 | 0.1119 | 5.23 | 3.46 | 0 | 0.001 |
117 | Unnamed road, Hume | 1349 | 1272 | 1464 | 27.41 | 25.07 | 25.33 | 6.11 | 5.7 | 6.49 | 0.1664 | 0.1599 | 0.1696 | 10.17 | 8.74 | 0 | 0 |
120 | Auchencrow | 593 | 593 | 901 | 20.7 | 18.38 | 19.08 | 5.39 | 4.3 | 4.9 | 0.2212 | 0.1766 | 0.1632 | 8.2 | 5.93 | 0 | 0 |
121 | Nether Blainslie (near Lauder) | 1299 | 890 | 1729 | 26.38 | 23.71 | 21.67 | 8.36 | 6.8 | 7.27 | 0.232 | 0.2281 | 0.1748 | 8.19 | 16.17 | 0 | 0 |
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Survey Wave | n | Minimum | Maximum | Average | Std. Deviation | ||||
---|---|---|---|---|---|---|---|---|---|
Mean | 85th Percentile | Mean | 85th Percentile | Mean | 85th Percentile | Mean | 85th Percentile | ||
Survey 1 (“before”) | 109 | 14.50 | 18.10 | 34.80 | 42.40 | 25.33 | 30.21 | 4.564 | 4.896 |
Survey 2 (“after I”) | 109 | 14.20 | 17.30 | 27.60 | 34.10 | 22.22 | 27.03 | 3.018 | 3.753 |
Survey 4 (“after III”) | 109 | 13.50 | 16.20 | 30.20 | 35.60 | 22.64 | 27.59 | 3.274 | 3.932 |
Speed Band (mph) | Survey Wave | n | Minimum | Maximum | Average | Std. Deviation | ||||
---|---|---|---|---|---|---|---|---|---|---|
Mean | 85th Percentile | Mean | 85th Percentile | Mean | 85th Percentile | Mean | 85th Percentile | |||
0–20 | Survey 1 (“before”) | 20 | 14.50 | 18.10 | 20.00 | 26.10 | 18.06 | 22.22 | 1.671 | 2.193 |
Survey 2 (“after I”) | 20 | 14.20 | 17.30 | 20.50 | 25.30 | 17.41 | 21.36 | 1.781 | 2.252 | |
Survey 4 (“after III”) | 20 | 13.50 | 16.20 | 26.00 | 33.20 | 18.01 | 22.13 | 2.835 | 3.626 | |
>20–25 | Survey 1 (“before”) | 24 | 20.60 | 25.90 | 25.00 | 30.80 | 22.58 | 27.98 | 1.266 | 1.380 |
Survey 2 (“after I”) | 24 | 18.40 | 22.90 | 24.10 | 28.80 | 21.01 | 25.78 | 1.231 | 1.429 | |
Survey 4 (“after III”) | 24 | 18.40 | 23.30 | 24.00 | 30.00 | 21.12 | 26.04 | 1.706 | 1.832 | |
>25–30 | Survey 1 (“before”) | 52 | 25.20 | 29.40 | 30.00 | 36.40 | 27.94 | 32.74 | 1.412 | 1.654 |
Survey 2 (“after I”) | 52 | 21.10 | 24.10 | 26.90 | 34.10 | 23.71 | 28.60 | 1.293 | 2.131 | |
Survey 4 (“after III”) | 52 | 21.60 | 25.90 | 27.70 | 33.50 | 24.17 | 29.18 | 1.486 | 1.961 | |
>30–35 | Survey 1 (“before”) | 13 | 30.10 | 33.80 | 34.80 | 42.40 | 31.17 | 36.52 | 1.363 | 2.348 |
Survey 2 (“after I”) | 13 | 24.30 | 29.10 | 27.60 | 34.10 | 25.87 | 31.83 | 1.131 | 1.772 | |
Survey 4 (“after III”) | 13 | 24.90 | 30.00 | 30.20 | 35.60 | 26.45 | 32.47 | 1.581 | 2.042 |
Survey Wave | n | Average Traffic Volume (Vehicles) | >PSL | >ACPO | >DfT |
---|---|---|---|---|---|
Survey 1 (“before”) | 109 | 2383 | 25% | 7% | 0.04% |
Survey 2 (“after I”) | 109 | 1820 | 64% | 33% | 2% |
Survey 4 (“after III”) | 109 | 2506 | 68% | 38% | 3% |
“Before” vs. “after I” Comparison | |||
Wilcoxon Signed-Rank Test | n | Mean Rank | Sum of Ranks |
Sites with speed decrease | 108 | 60.10 | 6491.00 |
Sites with speed increase | 6 | 10.67 | 64.00 |
Ties | 1 | ||
Before” vs. “after III” Comparison | |||
Wilcoxon Signed-Rank Test | n | Mean Rank | Sum of Ranks |
Sites with speed decrease | 101 | 56.15 | 5671.00 |
Sites with speed increase | 7 | 30.71 | 215.00 |
Ties | 1 |
Key Variable | Mean | Standard Deviation | Minimum | Maximum |
---|---|---|---|---|
Mean speed (mph) | 23.48 | 3.85 | 13.50 | 34.80 |
85th percentile speed (mph) | 28.37 | 4.36 | 16.20 | 42.40 |
20 mph indicator (1 if 20 mph speed limit is in place, 0 otherwise) | 66.67% | - | 0.00 | 1.00 |
Average traffic volume (103 vehicles/day) | 2.256 | 2.772 | 0.055 | 18.391 |
Mean Speed | 85th Percentile Speed | |||||||
---|---|---|---|---|---|---|---|---|
Coefficient | t-Statistic | 95% Confidence Interval | Coefficient | t-Statistic | 95% Confidence Interval | |||
Intercept | 24.454 | 66.77 | 23.736 | 25.172 | 29.609 | 68.03 | 28.756 | 30.462 |
20 mph indicator (1 if 20 mph limit is in place, 0 otherwise) | −2.836 | −7.07 | −3.622 | −2.049 | −2.863 | −6.01 | −3.798 | −1.929 |
Average traffic volume (103 vehicles/day) | 0.410 | 5.95 | 0.270 | 0.540 | 0.300 | 3.64 | 0.140 | 0.450 |
Log-likelihood at zero | −903.893 | −944.715 | ||||||
Log-likelihood at convergence | −864.335 | −920.779 | ||||||
Likelihood Ratio Test (LRT) results | 79.11 | 47.87 | ||||||
F-test results | 44.34 | 25.54 |
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Olowosegun, A.; Fountas, G.; Davis, A. Assessing the Impact of 20 mph Speed Limits on Vehicle Speeds in Rural Areas: The Case of the Scottish Borders. Safety 2023, 9, 66. https://doi.org/10.3390/safety9030066
Olowosegun A, Fountas G, Davis A. Assessing the Impact of 20 mph Speed Limits on Vehicle Speeds in Rural Areas: The Case of the Scottish Borders. Safety. 2023; 9(3):66. https://doi.org/10.3390/safety9030066
Chicago/Turabian StyleOlowosegun, Adebola, Grigorios Fountas, and Adrian Davis. 2023. "Assessing the Impact of 20 mph Speed Limits on Vehicle Speeds in Rural Areas: The Case of the Scottish Borders" Safety 9, no. 3: 66. https://doi.org/10.3390/safety9030066