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Publication Number: FHWA-RD-03-037
Date: May 2005

Validation of Accident Models for Intersections

FHWA Contact: John Doremi,
HRDI-10, (202) 493-3052, John.doremi@dot.gov

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3. RECALIBRATION (Continuation)

3.5.3 Summary of AMFs

This research introduced two ways of deriving AMFs. One approach is to adopt the estimated parameter values from the statistically significant variables in the accident prediction models. The other approach uses a relatively untested regression procedure. Although in general the first approach is easier to apply, the second approach is recommended. This approach aims to attribute the difference between the observed number of crashes at a site and that predicted by a base model to the presence of non-base condition factors. This difference will explain a real effect of the presence of individual design features on safety.

Tables 185 through 187 compare the AMFs from the "Red Book" and those derived here. The AMFs from Harwood et al. are also shown in brackets.(5) As mentioned, none of the variables investigated showed any significant impact on safety for Type V sites, resulting in AMFs of one for these variables.

Compared to the previous works, for Types I and II, no AMF was estimated for SKEW. For right-turn lane on major roads, AMFs greater than one and less than one were estimated for Type II sites using the Group A dataset for the former and the Group B for the latter.

Whereas the "Red Book" provides separate AMFs for right-and left-turn lanes on major roads at Type II intersections, turning lanes at most sits in this dataset were provided on both approaches and separate effects could not be detected for one versus two approaches. SKEW did not provide a significant AMF different from 1 in the new data. And very few sites had deficient sight distance so an AMF could not be estimated.

For Type III and IV intersections, intersection angle (SKEW) was estimated as significant in the regression models. Right-turn lanes on major roads provided significant AMFs for Type IV intersections. For Type V intersections, no AMFs were found to be significantly different from 1.

Table 185. Comparison of Type I-II AMFs for TOTACC

AMF

"Red Book" and Harwood et al. (2002)

Full Models

Regression Models

Type I

Type II

Type I

Type II

Type I

Type II

SKEW

exp(0.004SKEW)

exp(0.0054SKEW)

Not calibrated

Not calibrated

1

RT MAJ

1.00 if none exist

0.95 on one approach

(0.86 on one approach)

0.90 on both approaches

(0.74 on both approaches)

0.88

1.19,0.861

0.71

LT MAJ

1.00 if none exist

0.78 if at least one exists

(0.56 if at least one exists)

1.00 if none exist

0.76 on one approach

(0.72 on one approach)

0.58 on both approaches

(0.52 on both approaches)

0.82

 

0.71

SIGHT DISTANCE

1.05 if limited in 1 quadrants

Not calibrated

Not calibrated

Not calibrated

Not calibrated

1.10 if limited in 2 quadrants

1.15 if limited in 3 quadrants

1.20 if limited in 4 quadrants

RT MIN

Not calibrated

Not calibrated

1.35

Not calibrated

1.48

HI1

exp(0.0263)

Not calibrated

Not calibrated

DRWY1

Not calibrated

1.13

MEDIAN

Not calibrated

1

0.77

1 Group A = 1.19, Group B = 0.86

Table 186. Comparison of Type III-V AMFs for TOTACC

AMF

"Red Book" and Harwood et al. (2002)

AMFs Derived From Full Models

AMFs Derived From Regression Models

Type III-IV

Type V

Type III

Type IV

Type V

Type III

Type IV

Type V

SKEW

None provided

exp(0.010SKEW) 

Not calibrated

Not calibrated

1+(0.016*SKEW)/ (0.98+0.016*SKEW)

1+(0.053*SKEW)/ (1.43+0.053*SKEW)

1

RT MAJ

1.00 if none exist

0.975 on one approach (0.96 on one approach)

0.95 on both approaches (0.92 on both approaches)

Not calibrated

1

1

1

LT MAJ

1.00 if none exist

0.82 on one approach

0.67 on both approaches

0.71

1

1

SIGHT DISTANCE

1

1

1

1

COMDRWY1

Not calibrated 

exp (0.0681COMDRWY1)

exp (0.0539 COMDRWY1)

Not calibrated

Not calibrated

Not calibrated

VEI1

exp(0.1081VEI1)

Not calibrated 

MEDWIDTH1

exp (-0.0106MEDWDTH1)

MEDTYPE1

0.73

PKTRUCK

Not calibrated

exp (-0.0479PKTRUCK)

PKTHRU2

exp (0.0249PKTHRU2)

PKLEFT

exp (0.0229PKLEFT)

SDR2

exp(-0.0003SDR2)

LIGHT

 

0.75

HEICOM

exp (-0.0288HEICOM)

Table 187. Comparison of AMFs for INJACC

AMF

"Red Book"

AMFs Derived From Full Models

AMFs Derived From Regression Models

Type I - V

Type I

Type II

Type III

Type IV

Type V

Type I

Type II

Type III

Type IV

SKEW

None provided

Not calibrated

Not calibrated

exp(0.0163SKEW)

Not calibrated 

Not calibrated 

1

1

1+(0.017SKEW)/ (0.52+0.017SKEW)

1+(0.048SKEW)/ (0.72+0.048SKEW)

RT MAJ

0.87

0.85

Not calibrated 

1

1

1

0.86 one approach, 0.74 both approaches

LT MAJ

0.8

Not calibrated

1

0.42

1

1

RT MIN

1.36

1.56

1

1

1

SIGHT DISTANCE

 Not calibrated

Not calibrated

Not calibrated

1

1

HI

exp (0.0286)

exp (0.0408)

Not calibrated

Not calibrated

DRWY1

Not calibrated 

1.09

MEDIAN

0.72

1

0.52

COMDRWY1

Not calibrated

exp (0.0627COMDRWY1)

Not calibrated

Not calibrated

HAZRAT1

exp (0.1889HAZRAT1) 

PKTRUCK

exp (-0.0253PKTRUCK)

exp (-0.0520PKTRUCK) 

PKTURN

exp(0.0254PKTURN)

Not calibrated

PKLEFT1

Not calibrated

exp (0.0523PKLEF)

SDR2

Not calibrated

LIGHT

0.67

HEI2

exp (-0.0284HEI2)


3.6 SENSITIVITY ANALYSIS RESULTS

A sensitivity analysis was performed to examine the estimated effect on safety of the AMFs derived from the full models and regression base models. The sensitivity analysis

applies each AMF to the base model estimate for various levels of AADT.

3.6.1 Type I Intersections

The predicted TOTAL and INJURY accident frequencies per year for each AMF derived from the full models and regression base models are presented in tables 188 through 195.

Type I TOTAL Accidents

The AMFs derived for TOTAL accidents for Type I intersections are HI1, right-turn lanes on major, right-turn lane on minor, and left-turn lanes on major roads. The sensitivity test results for these AMFs are presented in tables 188 through 191.

Table 188. Sensitivity of Safety to HI1 for Type I TOTAL Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

HI1

0

5

10

20

400

50

0.088

0.101

0.115

0.150

100

0.113

0.129

0.147

0.191

400

0.185

0.211

0.240

0.312

1,000

100

0.204

0.233

0.265

0.345

500

0.361

0.411

0.469

0.610

1,000

0.461

0.526

0.600

0.780

3,000

100

0.414

0.472

0.539

0.701

500

0.732

0.835

0.952

1.239

1,000

0.936

1.067

1.217

1.583

3,000

1.380

1.574

1.796

2.336

5,000

100

0.576

0.656

0.749

0.974

500

1.017

1.160

1.324

1.722

1,000

1.300

1.483

1.692

2.200

3,000

1.919

2.188

2.496

3.247

5,000

2.299

2.622

2.990

3.890

10,000

100

0.900

1.026

1.170

1.522

500

1.590

1.814

2.069

2.691

1,000

2.033

2.318

2.644

3.440

3,000

2.999

3.421

3.901

5.075

5,000

3.594

4.099

4.675

6.081

10,000

4.593

5.238

5.975

7.772

Note: Group B AADT base model was used.

The AMF for HI1 was derived from full models.

Table 189. Sensitivity of Safety to RT MAJ for Type I TOTAL Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

RT MAJ

No Right-Turn Lane on Major Road

Presence of Right-Turn Lane on Major Road

400

50

0.088

0.078

100

0.113

0.099

400

0.185

0.162

1,000

100

0.204

0.180

500

0.361

0.317

1,000

0.461

0.406

3,000

100

0.414

0.364

500

0.732

0.644

1,000

0.936

0.823

3,000

1.380

1.215

5,000

100

0.576

0.506

500

1.017

0.895

1,000

1.300

1.144

3,000

1.919

1.688

5,000

2.299

2.023

10,000

100

0.900

0.792

500

1.590

1.400

1,000

2.033

1.789

3,000

2.999

2.639

5,000

3.594

3.162

10,000

4.593

4.042

Note: Group B AADT base model was used.

The AMF for RT MAJ was derived from full models.

Table 190. Sensitivity of Safety to RT MIN for Type I TOTAL Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

RT MIN

No Right-Turn Lane on Minor Road

Presence of Right-Turn Lane on Minor Road

A

B

400

50

0.088

0.119

0.131

100

0.113

0.153

0.167

400

0.185

0.249

0.273

1,000

100

0.204

0.275

0.302

500

0.361

0.487

0.534

1,000

0.461

0.622

0.682

3,000

100

0.414

0.559

0.613

500

0.732

0.988

1.083

1,000

0.936

1.263

1.385

3,000

1.380

1.864

2.043

5,000

100

0.576

0.777

0.852

500

1.017

1.374

1.506

1,000

1.300

1.756

1.925

3,000

1.919

2.590

2.839

5,000

2.299

3.103

3.402

10,000

100

0.900

1.215

1.332

500

1.590

2.147

2.354

1,000

2.033

2.744

3.099

3,000

2.999

4.049

4.439

5,000

3.594

4.851

5.319

10,000

4.593

6.200

6.798

Note: Group B AADT base model was used.

A: AMF derived from full models.

B: AMF derived from regression models.

Table 191. Sensitivity of Safety to LT MAJ for Type I TOTAL Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

LT MAJ

No Left-Turn Lane on Major Road

Presence of Left-Turn Lane on Major Road

400

50

0.088

0.073

100

0.113

0.093

400

0.185

0.151

1,000

100

0.204

0.167

500

0.361

0.296

1,000

0.461

0.378

3,000

100

0.414

0.340

500

0.732

0.600

1,000

0.936

0.767

3,000

1.380

1.132

5,000

100

0.576

0.472

500

1.017

0.834

1,000

1.300

1.066

3,000

1.919

1.573

5,000

2.299

1.885

10,000

100

0.900

0.738

500

1.590

1.304

1,000

2.033

1.667

3,000

2.999

2.459

5,000

3.594

2.947

10,000

4.593

3.766

Note: Group B AADT base model was used.

The AMF for LT MAJ was derived from full models.

Type I INJURY Accidents

The AMFs derived for INJURY accidents for Type I intersections are HI1, right-turn lane on major, right-turn lanes on minor, and left-turn lanes on major roads. The sensitivity test results for these AMFs are presented in tables 192 through 195.

Table 192. Sensitivity of Safety to HI1 for Type I INJURY Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

HI1

0

5

10

20

400

50

0.036

0.042

0.048

0.064

100

0.046

0.053

0.061

0.081

400

0.073

0.084

0.097

0.129

1,000

100

0.082

0.095

0.109

0.145

500

0.142

0.163

0.188

0.251

1,000

0.179

0.206

0.238

0.317

3,000

100

0.166

0.192

0.221

0.295

500

0.287

0.331

0.382

0.508

1,000

0.362

0.418

0.482

0.642

3,000

0.526

0.606

0.700

0.931

5,000

100

0.231

0.266

0.307

0.409

500

0.398

0.459

0.530

0.705

1,000

0.503

0.581

0.670

0.892

3,000

0.730

0.842

0.971

1.293

5,000

0.867

1.001

1.154

1.537

10,000

100

0.361

0.416

0.480

0.639

500

0.621

0.717

0.827

1.101

1,000

0.786

0.906

1.046

1.392

3,000

1.139

1.314

1.516

2.018

5,000

1.354

1.562

1.802

2.399

10,000

1.712

1.975

2.278

3.033

Note: Group B AADT base model was used.

The AMF for HI1 was derived from full models.

Table 193. Sensitivity of Safety to RT MAJ for Type I INJURY Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

RT MAJ

No Right-Turn Lane on Major Road

Presence of Right-Turn Lane on Major Road

400

50

0.036

0.031

100

0.046

0.040

400

0.073

0.063

1,000

100

0.082

0.071

500

0.142

0.123

1,000

0.179

0.156

3,000

100

0.166

0.145

500

0.287

0.249

1,000

0.362

0.315

3,000

0.526

0.457

5,000

100

0.231

0.201

500

0.398

0.346

1,000

0.503

0.438

3,000

0.730

0.635

5,000

0.867

0.755

10,000

100

0.361

0.314

500

0.621

0.541

1,000

0.786

0.684

3,000

1.139

0.991

5,000

1.354

1.178

10,000

1.712

1.489

Note: Group B AADT base model was used.

The AMF for RT MAJ was derived from full models.

Table 194. Sensitivity of Safety to RT MIN for Type I INJURY Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

RT MIN

No right-turn lane on minor road

Presence of right-turn lane on minor road

A

B

400

50

0.036

0.049

0.056

100

0.046

0.062

0.071

400

0.073

0.099

0.114

1,000

100

0.082

0.112

0.128

500

0.142

0.192

0.221

1,000

0.179

0.243

0.279

3,000

100

0.166

0.226

0.260

500

0.287

0.390

0.447

1,000

0.362

0.493

0.565

3,000

0.526

0.715

0.820

5,000

100

0.231

0.314

0.360

500

0.398

0.541

0.621

1,000

0.503

0.684

0.785

3,000

0.730

0.992

1.138

5,000

0.867

1.180

1.353

10,000

100

0.361

0.490

0.563

500

0.621

0.845

0.970

1,000

0.786

1.068

1.226

3,000

1.139

1.549

1.777

5,000

1.354

1.841

2.112

10,000

1.712

2.328

2.670

Note: Group B AADT base model was used.

A: AMF derived from full models.

B: AMF derived from regression models.

Table 195. Sensitivity of Safety to LT MAJ for Type I INJURY Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

LT MAJ

No Left-Turn Lane on Major Road

Presence of Left-Turn Lane on Major Road

400

50

0.036

0.029

100

0.046

0.036

400

0.073

0.058

1,000

100

0.082

0.066

500

0.142

0.113

1,000

0.179

0.143

3,000

100

0.166

0.133

500

0.287

0.229

1,000

0.362

0.290

3,000

0.526

0.420

5,000

100

0.231

0.185

500

0.398

0.318

1,000

0.503

0.403

3,000

0.730

0.584

5,000

0.867

0.694

10,000

100

0.361

0.288

500

0.621

0.497

1,000

0.786

0.629

3,000

1.139

0.911

5,000

1.354

1.083

10,000

1.712

1.369

Note: Group B AADT base model was used.

The AMF for LT MAJ was derived from full models.

3.6.2 Type II Intersections

The predicted TOTAL and INJURY accident frequencies per year for each AMF derived from the full models and regression base models are presented in tables 196 through 204.

Type II TOTAL Accidents

The AMFs derived for TOTAL accidents for Type II intersections are ND, right-turn lanes on major, left-turn lanes on major, and median on major roads. The sensitivity test results for these AMFs are presented in tables 196 through 199.

Table 196. Sensitivity of Safety to DRWY1 for Type II TOTAL Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

DRWY1

0

3

5

400

50

0.056

0.064

0.072

100

0.082

0.093

0.105

400

0.175

0.198

0.223

1,000

100

0.158

0.179

0.202

500

0.380

0.429

0.485

1,000

0.554

0.626

0.707

3,000

100

0.346

0.391

0.442

500

0.831

0.939

1.061

1,000

1.212

1.369

1.548

3,000

2.204

2.491

2.815

5,000

100

0.498

0.563

0.636

500

1.196

1.351

1.527

1,000

1.744

1.971

2.227

3,000

3.173

3.585

4.051

5,000

4.190

4.735

5.350

10,000

100

0.816

0.922

1.042

500

1.960

2.215

2.503

1,000

2.859

3.230

3.650

3,000

5.200

5.876

6.639

5,000

6.867

7.760

8.769

10,000

10.016

11.318

12.789

Note: Group B AADT base model was used.

The AMF for DRWY1 was derived from full models.

Table 197. Sensitivity of Safety to RT MAJ for Type II TOTAL Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

RT MAJ

No Right-Turn Lane on Major Road

Presence of Right-Turn Lane on Major Road

A

B

C

400

50

0.056

0.067

0.049

0.040

100

0.082

0.098

0.071

0.058

400

0.175

0.208

0.151

0.124

1,000

100

0.158

0.188

0.136

0.112

500

0.380

0.452

0.327

0.270

1,000

0.554

0.659

0.476

0.393

3,000

100

0.346

0.412

0.297

0.246

500

0.831

0.989

0.715

0.590

1,000

1.212

1.442

1.042

0.860

3,000

2.204

2.623

1.896

1.565

5,000

100

0.498

0.592

0.428

0.353

500

1.196

1.423

1.028

0.849

1,000

1.744

2.076

1.500

1.238

3,000

3.173

3.775

2.728

2.252

5,000

4.190

4.986

3.603

2.975

10,000

100

0.816

0.971

0.702

0.579

500

1.960

2.332

1.686

1.392

1,000

2.859

3.402

2.459

2.030

3,000

5.200

6.188

4.472

3.692

5,000

6.867

8.172

5.906

4.876

10,000

10.016

11.919

8.614

7.111

Note: Group B AADT base model was used.

A: AMF derived from full models, Group A data.

B: AMF derived from full models, Group B data.

C: AMF derived from regression models

Table 198. Sensitivity of Safety to LT MAJ for Type II TOTAL Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

LT MAJ

No Left-Turn Lane on Major Road

Presence of Left-Turn Lane on Major Road

400

50

0.056

0.040

100

0.082

0.058

400

0.175

0.124

1,000

100

0.158

0.112

500

0.380

0.270

1,000

0.554

0.393

3,000

100

0.346

0.246

500

0.831

0.590

1,000

1.212

0.860

3,000

2.204

1.565

5,000

100

0.498

0.353

500

1.196

0.8449

1,000

1.744

1.238

3,000

3.173

2.252

5,000

4.190

2.975

10,000

100

0.816

0.579

500

1.960

1.392

1,000

2.859

2.030

3,000

5.200

3.692

5,000

6.867

4.876

10,000

10.016

7.111

Note: Group B AADT base model was used.

The AMF for LT MAJ was derived from regression models.

Table 199. Sensitivity of Safety to MEDIAN for Type II TOTAL Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

MEDIAN

No Median on Major Road

Presence of Median on Major Road

400

50

0.056

0.043

100

0.082

0.063

400

0.175

0.135

1,000

100

0.158

0.122

500

0.380

0.292

1,000

0.554

0.426

3,000

100

0.346

0.266

500

0.831

0.640

1,000

1.212

0.933

3,000

2.204

1.697

5,000

100

0.498

0.383

500

1.196

0.921

1,000

1.744

1.343

3,000

3.173

2.443

5,000

4.190

3.226

10,000

100

0.816

0.628

500

1.960

1.509

1,000

2.859

2.201

3,000

5.200

4.004

5,000

6.867

5.288

10,000

10.016

7.712

Note: Group B AADT base model was used.

The AMF for MEDIAN was derived from regression models.

Type II INJURY Accidents

The AMFs derived for INJURY accidents for Type II intersections are HI1, DRWY1, right-turn lanes on major, left-turn lanes on major, and median on major roads. The sensitivity test results for these AMFs are presented in tables 200 through 204.

Table 200. Sensitivity of Safety to HI1 for Type II INJURY Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

HI1

0

5

10

20

400

50

0.033

0.040

0.049

0.074

100

0.049

0.060

0.073

0.110

400

0.107

0.131

0.161

0.242

1,000

100

0.087

0.106

0.130

0.196

500

0.216

0.265

0.325

0.489

1,000

0.321

0.394

0.483

0.726

3,000

100

0.173

0.212

0.259

0.390

500

0.431

0.529

0.649

0.975

1,000

0.640

0.785

0.962

1.447

3,000

1.196

1.466

1.798

2.704

5,000

100

0.238

0.292

0.358

0.538

500

0.594

0.729

0.894

1.344

1,000

0.882

1.082

1.326

1.995

3,000

1.648

2.021

2.479

3.727

5,000

2.204

2.703

3.315

4.985

10,000

100

0.368

0.451

0.553

0.831

500

0.919

1.127

1.382

2.078

1,000

1.363

1.672

2.050

3.083

3,000

2.548

3.124

3.831

5.761

5,000

3.407

4.178

5.124

7.705

10,000

5.055

6.199

7.602

11.433

Note: Group B AADT base model was used.

The AMF for HI1 was derived from full models.

Table 201. Sensitivity of Safety to DRWY1 for Type II INJURY Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

DRWY1

0

3

5

400

50

0.033

0.036

0.039

100

0.049

0.053

0.058

400

0.107

0.117

0.127

1,000

100

0.087

0.094

0.103

500

0.216

0.236

0.257

1,000

0.321

0.350

0.381

3,000

100

0.173

0.188

0.205

500

0.431

0.470

0.512

1,000

0.640

0.697

0.760

3,000

1.196

1.303

1.421

5,000

100

0.238

0.259

0.283

500

0.594

0.648

0.706

1,000

0.882

0.961

1.048

3,000

1.648

1.797

1.958

5,000

2.204

2.403

2.619

10,000

100

0.368

0.401

0.437

500

0.919

1.001

1.092

1,000

1.363

1.486

1.620

3,000

2.548

2.777

3.027

5,000

3.407

3.714

4.048

10,000

5.055

5.510

6.006

Note: Group B AADT base model was used.

The AMF for DRWY1 was derived from full models.

Table 202. Sensitivity of Safety to RT MAJ for Type II INJURY Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

RT MAJ

No Right-Turn Lane on Major Road

Presence of Right-Turn Lane on Major Road

400

50

0.033

0.028

100

0.049

0.041

400

0.107

0.091

1,000

100

0.087

0.074

500

0.216

0.184

1,000

0.321

0.273

3,000

100

0.173

0.147

500

0.431

0.367

1,000

0.640

0.544

3,000

1.196

1.016

5,000

100

0.238

0.202

500

0.594

0.505

1,000

0.882

0.750

3,000

1.648

1.401

5,000

2.204

1.874

10,000

100

0.368

0.312

500

0.919

0.781

1,000

1.363

1.159

3,000

2.548

2.165

5,000

3.407

2.896

10,000

5.055

4.297

Note: Group B AADT base model was used.

The AMF for RT MAJ was derived from full models.

Table 203. Sensitivity of Safety to LT MAJ for Type II INJURY Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

LT MAJ

No Left-Turn Lane on Major Road

Presence of Left-Turn Lane on Major Road

400

50

0.033

0.014

100

0.049

0.020

400

0.107

0.045

1,000

100

0.087

0.036

500

0.216

0.091

1,000

0.321

0.135

3,000

100

0.173

0.072

500

0.431

0.181

1,000

0.640

0.269

3,000

1.196

0.502

5,000

100

0.238

0.100

500

0.594

0.250

1,000

0.882

0.370

3,000

1.648

0.692

5,000

2.204

0.926

10,000

100

0.368

0.154

500

0.919

0.386

1,000

1.363

0.573

3,000

2.548

1.070

5,000

3.407

1.431

10,000

5.055

2.123

Note: Group B AADT base model was used.

The AMF for LT MAJ was derived from regression models.

Table 204. Sensitivity of Safety to MEDIAN for Type II INJURY Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

MEDIAN

No Median on Major Road

Presence of Median on Major Road

A

B

400

50

0.033

0.024

0.017

100

0.049

0.035

0.025

400

0.107

0.077

0.056

1,000

100

0.087

0.062

0.045

500

0.216

0.156

0.112

1,000

0.321

0.231

0.167

3,000

100

0.173

0.124

0.090

500

0.431

0.311

0.224

1,000

0.640

0.461

0.333

3,000

1.196

0.861

0.622

5,000

100

0.238

0.171

0.124

500

0.594

0.428

0.309

1,000

0.882

0.635

0.459

3,000

1.648

1.187

0.857

5,000

2.204

1.587

1.146

10,000

100

0.368

0.265

0.191

500

0.919

0.662

0.478

1,000

1.363

0.981

0.709

3,000

2.548

1.834

1.325

5,000

3.407

2.453

1.772

10,000

5.055

3.640

2.629

Note: Group B AADT base model was used.

A: AMF derived from full models.

B: AMF derived from regression models.

3.6.3 Type III Intersections

The predicted TOTAL and INJURY accident frequencies per year for each AMF derived from the full models and regression base models are presented in tables 205 through 215.

Type III TOTAL Accidents

The AMFs derived for TOTAL accidents for Type III intersections are intersection SKEW angle, commercial driveways on major road, vertical curves on major road, median width on major road, painted median type on major road, and major road left-turn lane. The sensitivity test results for these AMFs are presented in tables 205 through 210.

Table 205. Sensitivity of Safety to Skew Angles for Type III TOTAL Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

SKEW Angle (degrees)

A

B

A

B

A

B

A

B

A

B

0

10

15

30

45

400

50

0.01

0.01

0.01

0.01

0.01

0.01

0.01

0.01

0.02

0.01

100

0.01

0.01

0.01

0.01

0.01

0.01

0.02

0.02

0.02

0.02

400

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.03

0.02

1,000

100

0.03

0.03

0.04

0.04

0.04

0.04

0.05

0.04

0.05

0.05

500

0.05

0.05

0.06

0.06

0.06

0.06

0.07

0.07

0.08

0.07

1,000

0.06

0.06

0.07

0.07

0.07

0.07

0.08

0.08

0.09

0.09

3,000

100

0.11

0.11

0.12

0.13

0.13

0.13

0.15

0.15

0.17

0.16

500

0.17

0.17

0.18

0.19

0.19

0.20

0.23

0.22

0.26

0.24

1,000

0.20

0.20

0.22

0.23

0.23

0.24

0.27

0.26

0.31

0.28

3,000

0.26

0.26

0.29

0.30

0.31

0.31

0.36

0.35

0.41

0.37

5,000

100

0.19

0.19

0.21

0.22

0.23

0.23

0.26

0.26

0.30

0.28

500

0.29

0.29

0.32

0.33

0.34

0.35

0.39

0.39

0.46

0.41

1,000

0.35

0.35

0.38

0.40

0.40

0.42

0.47

0.46

0.55

0.49

3,000

0.46

0.46

0.51

0.52

0.53

0.55

0.62

0.61

0.72

0.65

5,000

0.52

0.52

0.58

0.60

0.61

0.63

0.71

0.70

0.82

0.74

10,000

100

0.41

0.41

0.46

0.47

0.48

0.49

0.56

0.55

0.65

0.59

500

0.62

0.62

0.69

0.71

0.72

0.74

0.84

0.83

0.98

0.89

1,000

0.74

0.74

0.82

0.85

0.86

0.89

1.00

0.99

1.17

1.06

3,000

0.98

0.98

1.09

1.12

1.14

1.17

1.33

1.30

1.55

1.40

5,000

1.12

1.12

1.24

1.27

1.30

1.34

1.51

1.48

1.76

1.59

10,000

1.33

1.33

1.47

1.52

1.55

1.59

1.80

1.77

2.10

1.90

Note: Group B AADT base model was used.

A: AMF derived from full models.

B: AMF derived from regression models.


Table 206. Sensitivity of Safety to Commercial Driveways on Major Road forType III TOTAL Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

Commercial Driveways on Major Road (density)

0

5

10

15

400

50

0.01

0.01

0.02

0.03

100

0.01

0.02

0.02

0.03

400

0.02

0.02

0.03

0.05

1,000

100

0.03

0.05

0.07

0.09

500

0.05

0.07

0.10

0.14

1,000

0.06

0.08

0.12

0.17

3,000

100

0.11

0.16

0.22

0.31

500

0.17

0.23

0.33

0.46

1,000

0.20

0.28

0.39

0.55

3,000

0.26

0.37

0.52

0.73

5,000

100

0.19

0.27

0.38

0.54

500

0.29

0.41

0.58

0.81

1,000

0.35

0.49

0.69

0.96

3,000

0.46

0.65

0.91

1.28

5,000

0.52

0.74

1.03

1.45

10,000

100

0.41

0.58

0.82

1.15

500

0.62

0.87

1.23

1.73

1,000

0.74

1.04

1.47

2.06

3,000

0.98

1.38

1.94

2.72

5,000

1.12

1.57

2.21

3.10

10,000

1.33

1.87

2.63

3.70

Note: Group B AADT base model was used.

The AMF for CD on major road was derived from full models.

Table 207. Sensitivity of Safety to Vertical Curves on Major Road (VEI1) for Type III TOTAL Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

VEI1

0

3

5

10

400

50

0.01

0.01

0.02

0.03

100

0.01

0.02

0.02

0.04

400

0.02

0.02

0.03

0.05

1,000

100

0.03

0.05

0.06

0.10

500

0.05

0.07

0.09

0.15

1,000

0.06

0.08

0.10

0.18

3,000

100

0.11

0.15

0.19

0.33

500

0.17

0.23

0.29

0.49

1,000

0.20

0.27

0.34

0.59

3,000

0.26

0.36

0.45

0.77

5,000

100

0.19

0.27

0.33

0.57

500

0.29

0.40

0.50

0.86

1,000

0.35

0.48

0.60

1.02

3,000

0.46

0.64

0.79

1.35

5,000

0.52

0.72

0.90

1.54

10,000

100

0.41

0.57

0.71

1.22

500

0.62

0.86

1.07

1.83

1,000

0.74

1.03

1.27

2.19

3,000

0.98

1.36

1.68

2.89

5,000

1.12

1.54

1.92

3.29

10,000

1.33

1.84

2.29

3.93

Note: Group B AADT base model was used.

The AMF for VEI1 was derived from full models.

Table 208. Sensitivity of Safety to Median Width on Major Road (MEDWIDTH1) for Type III TOTAL Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

MEDWIDHT1

0

6

12

20

400

50

0.01

0.01

0.01

0.01

100

0.01

0.01

0.01

0.01

400

0.02

0.02

0.02

0.01

1,000

100

0.03

0.03

0.03

0.03

500

0.05

0.05

0.04

0.04

1,000

0.06

0.06

0.05

0.05

3,000

100

0.11

0.10

0.10

0.09

500

0.17

0.16

0.15

0.13

1,000

0.20

0.19

0.17

0.16

3,000

0.26

0.25

0.23

0.21

5,000

100

0.19

0.18

0.17

0.16

500

0.29

0.27

0.26

0.24

1,000

0.35

0.33

0.31

0.28

3,000

0.46

0.43

0.40

0.37

5,000

0.52

0.49

0.46

0.42

10,000

100

0.41

0.39

0.36

0.33

500

0.62

0.58

0.55

0.50

1,000

0.74

0.70

0.65

0.60

3,000

0.98

0.92

0.86

0.79

5,000

1.12

1.05

0.98

0.90

10,000

1.33

1.25

1.17

1.08

Note: Group B AADT base model was used.

The AMF for MEDWIDTH1 was derived from full models.

Table 209. Sensitivity of Safety to Painted Median Type on Major Road (MEDTYPE1) for Type III TOTAL Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

Median Type on Major Road

No Median

Painted Median

400

50

0.01

0.01

100

0.01

0.01

400

0.02

0.01

1,000

100

0.03

0.02

500

0.05

0.04

1,000

0.06

0.04

3,000

100

0.11

0.08

500

0.17

0.12

1,000

0.20

0.15

3,000

0.26

0.19

5,000

100

0.19

0.14

500

0.29

0.21

1,000

0.35

0.25

3,000

0.46

0.34

5,000

0.52

0.38

10,000

100

0.41

0.30

500

0.62

0.45

1,000

0.74

0.54

3,000

0.98

0.72

5,000

1.12

0.82

10,000

1.33

0.97

Note: Group B AADT base model was used.

The AMF for MEDTYPE1 was derived from full models.

Table 210. Sensitivity of Safety to Major Road Left-Turn Lane for Type III TOTAL Accidents Per Year

Major Road AADT (veh/day)

Minor Road AADT (veh/day)

Major Road Left-Turn Lane

No Left-Turn Lane

One Left-Turn Lane

400

50

0.01

0.01

100

0.01

0.01

400

0.02

0.01

1,000

100

0.03

0.02

500

0.05

0.04

1,000

0.06

0.04

3,000

100

0.11

0.08

500

0.17

0.12

1,000

0.20

0.14

3,000

0.26

0.19

5,000

100

0.19

0.14

500

0.29

0.21

1,000

0.35

0.25

3,000

0.46

0.33

5,000

0.52

0.37

10,000

100

0.41

0.29

500

0.62

0.44

1,000

0.74

0.53

3,000

0.98

0.70

5,000

1.12

0.79

10,000

1.33

0.95

Note: Group B AADT base model was used.

The AMF for Major Road Left-Turn Lane was derived from regression models.

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