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From page 385... ... 385 APPENDIX C: PROPOSED HSM FREEWAYS CHAPTER CHAPTER 18 -- PREDICTIVE METHOD FOR FREEWAYS TABLE OF CONTENTS List of Figures ................................................................................................................................ 387 List of Tables .................................................................................................................................. Read the entire page →
From page 386... ... 386 18.9. Calibration of the SPFs and SDFs to Local Conditions ........................................................ Read the entire page →
From page 387... ... 387 LIST OF FIGURES Figure 18-1. The HSM Predictive Method ...................................................................................... Read the entire page →
From page 388... ... 388 LIST OF TABLES Table 18-1. Urban Freeway Segment SPFs .................................................................................. Read the entire page →
From page 389... ... 389 Table 18-25. Coefficients for Median Width CMF–Speed-Change Lanes ..................................... Read the entire page →
From page 390... ... 390 Chapter 18 -- Predictive Method for Freeways 18.1. INTRODUCTION This chapter presents the predictive method for freeways. Read the entire page →
From page 391... ... 391 The predictive models used in this chapter are described in detail in Section 18.3. The variables that comprise the predictive models include a series of subscripts to describe precisely the conditions to which they apply. Read the entire page →
From page 392... ... 392 Classifying an area as urban, suburban, or rural is subject to the roadway characteristics, surrounding population, and surrounding land uses, and is at the analyst's discretion. In the HSM, the definition of "urban" and "rural" areas is based on Federal Highway Administration (FHWA) Read the entire page →
From page 393... ... 393  Eight-lane freeway segment (8) -- a length of roadway consisting of eight through lanes with a continuous cross section providing two directions of travel in which the opposing travel lanes are physically separated by either distance or a barrier. Read the entire page →
From page 394... ... 394 total, or by crash type or severity. This section describes the predictive model for freeway segments. Read the entire page →
From page 395... ... 395 Different CMFs are used in Equation 18-3 to Equation 18-6. The first term in parentheses in each equation recognizes that the influence of some features is unique to each crash type. Read the entire page →
From page 396... ... 396 pdoatnEXscpfiatnEXscpasatnEXscp NNN ,,,,,,,,,,,, += ( ) Read the entire page →
From page 397... ... 397 Define roadway limits and facility type. Define the period of study. Read the entire page →
From page 398... ... 398 There are 18 steps in the predictive method. In some situations, certain steps will not be needed because data are not available or the step is not applicable to the situation at hand. Read the entire page →
From page 399... ... 399  An existing roadway network, facility, or site for which alternative geometric design or traffic control features are proposed (for near-term conditions) and site traffic volumes are known. Read the entire page →
From page 400... ... 400  If AADT volume is available for only a single year, that same volume is assumed to apply to all years of the evaluation period.  If two or more years of AADT data are available, the AADT volumes for intervening years are computed by interpolation. Read the entire page →
From page 401... ... 401 Any site can be selected for evaluation because each site is considered to be independent of the other sites. However, good practice is to select the sites in an orderly manner, such as in the order of their physical occurrence in the direction of increasing milepost. Read the entire page →
From page 402... ... 402 Step 13 -- Apply site-specific EB Method (if applicable) and apply SDFs. Read the entire page →
From page 403... ... 403 The decision to apply the project-level EB Method was determined in Step 3. If this method is not used, then the project-level expected average crash frequency for each year of the study period is limited to the project-level predicted average crash frequency for that year, as computed in Step 11. Read the entire page →
From page 404... ... 404 s asatacaSe asatacaSe n N N * ,,,, ,,,, = Where: Ne, aS, ac, at, as = overall expected average crash frequency for all sites aS and all years in the study period (includes all cross sections ac, all crash types at, and all severities as) Read the entire page →
From page 405... ... 405 Taper point Exit Ramp with Taper Design Entrance Ramp with Parallel Design Ramp Exit Length Ramp Entrance Length * Read the entire page →
From page 406... ... 406  Presence of a horizontal curve on one or both roadbeds. If a curve is present, then the three data elements in the following list are needed. Read the entire page →
From page 407... ... 407 Increasing milepost travel direction Curve in both directions (concentric) Rules 1. Read the entire page →
From page 408... ... 408  Widths of lanes, outside shoulders, inside shoulders, and median. The first three elements represent an average for both roadbeds. Read the entire page →
From page 409... ... 409 Lib,1 Lib,2 Wof f ,in,1 Wof f ,in,2 Lib,4Lib,3 Wof f ,in,4 Wof f ,in,3 Wm WisReference line Increasing milepost Figure 18-6. Barrier Variables  Width of continuous median barrier, if present. Read the entire page →
From page 410... ... 410 Lwev = w eaving section length 2' 2' Lwev Figure 18-7. Type B Weaving Section and Length  Distance to nearest upstream entrance ramp in each travel direction. Read the entire page →
From page 411... ... 411 Segment Increasing mile post Begin milepost Xb,ent Xb,ext End milepost Xe,ext Xe,ent All measurements are to the marked gore point. Read the entire page →
From page 412... ... 412 Tree Tree Tree Fence line Whc,1 Whc, 2 Increasing milepost Whc, 3 Lone tree not considered Guardrail not considered Median Reference line Whc = clear zone width Figure 18-9. Clear Zone Width Considerations  Proportion of freeway AADT volume that occurs during hours where the lane volume exceeds 1,000 vehicles per hour per lane (veh/h/ln) Read the entire page →
From page 413... ... 413 PLAN VIEW COMPONENT PARTS Speed-Change Lane Speed-Change Lane Type: ramp entrance Type: ramp exit Seg. length = Len Seg. Read the entire page →
From page 414... ... 414  Outside shoulder width. Measure the outside shoulder width at successive points along the roadway. Read the entire page →
From page 415... ... 415 Seg. Read the entire page →
From page 416... ... 416 for the development of SPFs for use in the predictive method are addressed in the calibration procedure presented in Section B.1.2 in Appendix B to Part C Each SPF has an associated overdispersion parameter k. Read the entire page →
From page 417... ... 417  Inside shoulder width (paved) 6 ft  Median width 60 ft  Length of median barrier 0.0 mi (i.e., not present) Read the entire page →
From page 418... ... 418 will be serving opposing directions of travel. If there are two ramp exits, then they will be serving opposing directions of travel. Read the entire page →
From page 419... ... 419 0 3 6 9 12 0 50 100 150 200 250 AADT (1000s of veh/day) Read the entire page →
From page 420... ... 420 Table 18-6. Default Distribution of Multiple-Vehicle Crashes by Crash Type for Freeway Segments Area Type Crash Type Category Proportion of Crashes by Severity Fatal and Injury Property Damage Only Rural Head-on 0.018 0.004 Right-angle 0.056 0.030 Rear-end 0.630 0.508 Sideswipe 0.237 0.380 Other multiple-vehicle crashes 0.059 0.078 Urban Head-on 0.008 0.002 Right-angle 0.031 0.018 Rear-end 0.750 0.690 Sideswipe 0.180 0.266 Other multiple-vehicle crashes 0.031 0.024 Single-Vehicle Crashes The base conditions for the SPFs for single-vehicle crashes on freeway segments are presented in the following list. Read the entire page →
From page 421... ... 421 0 1 2 3 4 5 0 50 100 150 200 250 AADT (1000s of veh/day) Read the entire page →
From page 422... ... 422 The value of the overdispersion parameter associated with the SPFs for freeway segments is determined as a function of the segment length. This value is computed using Equation 18-19. Read the entire page →
From page 423... ... 423 The SPFs described in this section are directly applicable to speed-change lanes adjacent to freeways with an even number of through lanes. They can be extended to the evaluation of speed-change lanes adjacent to freeways with 5, 7, and 9 lanes using the procedure described in Section 18.6.1. Read the entire page →
From page 424... ... 424 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 200 250 AADT (1000s of veh/day) Read the entire page →
From page 425... ... 425 The value of the overdispersion parameter associated with the SPFs for ramp-entrance speed-change lanes is determined as a function of the speed-change lane length. This value is computed as: enzatnENsc zatnENsc LK k × = ,,, ,,, 1 Where: ksc, nEN, at, z = overdispersion parameter for ramp entrance speed-change lane on a freeway with n lanes, all crash types at, and severity z; and Ksc, nEN, at, z = inverse dispersion parameter for ramp entrance speed-change lane on a freeway with n lanes, all crash types at, and severity z (mi-1) Read the entire page →
From page 426... ... 426 Table 18-10. Default Distribution of Ramp-Entrance-Related Crashes by Crash Type Area Type Crash Type Crash Type Category Proportion of Crashes by Severity Fatal and Injury Property Damage Only Rural Multiple vehicle Head-on 0.021 0.004 Right-angle 0.032 0.013 Rear-end 0.351 0.260 Sideswipe 0.128 0.242 Other multiple-vehicle crash 0.011 0.040 Single vehicle Crash with animal 0.000 0.009 Crash with fixed object 0.245 0.296 Crash with other object 0.021 0.070 Crash with parked vehicle 0.021 0.000 Other single-vehicle crashes 0.170 0.066 Urban Multiple vehicle Head-on 0.004 0.001 Right-angle 0.019 0.016 Rear-end 0.543 0.530 Sideswipe 0.133 0.252 Other multiple-vehicle crash 0.017 0.015 Single vehicle Crash with animal 0.000 0.002 Crash with fixed object 0.194 0.129 Crash with other object 0.019 0.036 Crash with parked vehicle 0.004 0.003 Other single-vehicle crashes 0.067 0.016 Ramp Exit Speed-Change Lanes The base conditions for the SPFs for ramp exit speed-change lanes are the same as those for ramp entrance speed-change lanes, as described in the preceding subsection. Read the entire page →
From page 427... ... 427 0.0 0.1 0.2 0.3 0 40 80 120 AADT (1000s of veh/day) Read the entire page →
From page 428... ... 428 Ksc, nEX, at, z = inverse dispersion parameter for ramp exit speed-change lane on a freeway with n lanes, all crash types at, and severity z. The inverse dispersion parameter for speed-change lanes adjacent to freeways with 4, 6, 8, or 10 through lanes is provided in Table 18-11. Read the entire page →
From page 429... ... 429 18.7. CRASH MODIFICATION FACTORS This section describes the CMFs applicable to the SPFs presented in Section 18.6. Read the entire page →
From page 430... ... 430 weighted average barrier offset (as measured from the edge of the inside shoulder) must be computed. Read the entire page →
From page 432... ... 432 Table 18-15. Coefficients for Lane Width CMF–Freeway Segments Cross Section (x) Read the entire page →
From page 433... ... 433 CMF4, w, x, y, z -- Median Width Four CMFs are used to describe the relationship between median width and predicted crash frequency. The SPFs to which they apply are identified in the following list:  SPF for fatal-and-injury multiple-vehicle crashes, specified number of lanes (fs, n, mv, fi) Read the entire page →
From page 434... ... 434 CMF5, w, x, y, z -- Median Barrier Four CMFs are used to describe the relationship between median barrier presence and predicted crash frequency. The SPFs to which they apply are identified in the following list:  SPF for fatal-and-injury multiple-vehicle crashes, specified number of lanes (fs, n, mv, fi) Read the entire page →
From page 435... ... 435 A statistic was developed to describe the degree of volume concentration during peak hours of the average day. It represents the proportion of the AADT that occurs during hours where the volume exceeds 1,000 vehicles per hour per lane (veh/h/ln) Read the entire page →
From page 436... ... 436 CMF7, fs, ac, mv, z -- Lane Change Two CMFs are used to describe the relationship between lane change activity and predicted crash frequency. The SPFs to which they apply are identified in the following list:  SPF for fatal-and-injury multiple-vehicle crashes, specified number of lanes (fs, n, mv, fi) Read the entire page →
From page 437... ... 437 PwevB, inc = proportion of segment length within a Type B weaving section for travel in increasing milepost direction; PwevB, dec = proportion of segment length within a Type B weaving section for travel in decreasing milepost direction; Lwev, inc = weaving section length for travel in increasing milepost direction (may extend beyond segment boundaries) Read the entire page →
From page 438... ... 438 The variables PwevB, inc and PwevB, dec in Equation 18-31 and Equation 18-32, respectively, are computed as the ratio of the length of the weaving section in the segment to the length of the freeway segment Lfs. If the segment is wholly located in the weaving section, then this variable is equal to 1.0. Read the entire page →
From page 439... ... 439 The coefficients for Equation 18-35 are provided in Table 18-21. The variable Pc,i is computed as the ratio of the length of curve i in the segment to the length of the freeway segment Lfs. Read the entire page →
From page 440... ... 440 is lowered by the presence of rumble strips. This trend was not found in the calibration data for curved segments. Read the entire page →
From page 441... ... 441 The coefficient for Equation 18-39 is provided in Table 18-22. Guidance for computing the variables Pob and Wocb is provided in Section 18.7.3. Read the entire page →
From page 442... ... 442 The coefficient for Equation 18-40 is provided in Table 18-23. The variable Pc, i is computed as the ratio of the length of curve i in the speed-chanage lane to the length of the speed-change lane Len or Lex. Read the entire page →
From page 444... ... 444 Wicb = distance from edge of inside shoulder to barrier face (ft) Read the entire page →
From page 445... ... 445 Any cross section (ac) All types (at) Read the entire page →
From page 446... ... 446  SPF for property-damage-only crashes, ramp entrance, freeway lanes n (sc, nEN, at, pdo) Read the entire page →
From page 447... ... 447  SPF for property-damage-only crashes, ramp exit, freeway lanes n (sc, nEX, at, pdo) Read the entire page →
From page 448... ... 448  Outside barrier. These four CMFs include variables that describe the presence of barrier in the median or on the roadside. Read the entire page →
From page 449... ... 449 Wib = inside barrier width (measured from barrier face to barrier face) Read the entire page →
From page 450... ... 450 0.0=ibP As suggested by Equation 18-28, the calculation of Wicb is not required when Pib = 0.0. For segments or speed-change lanes with barrier on the roadside, the following equations should be used to estimate Wocb and Pob. Read the entire page →
From page 451... ... 451 Ne, w, x, y, j = expected average crash frequency for site type w, cross section or control type x, crash type y, and severity level j ( j = K: fatal, A: incapacitating injury, B: non-incapacitating injury, C: possible injury) (crashes/yr) Read the entire page →
From page 452... ... 452 Pob = proportion of segment length with a barrier present on the roadside (i.e., outside) ; Phv = proportion of AADT during hours where volume exceeds 1,000 veh/h/ln; Pir = proportion of segment length with rumble strips present on the inside shoulders; Por = proportion of segment length with rumble strips present on the outside shoulders; Pc, i = proportion of segment length with curve i; Wl = lane width (ft) Read the entire page →
From page 453... ... 453 The sign of a coefficient in Table 18-30 indicates the change in the proportion of crashes associated with a change in the corresponding variable. For example, the negative coefficient associated with barrier presence indicates that the proportion of fatal K crashes decreases with an increase in the proportion of barrier present in the segment. Read the entire page →
From page 454... ... 454  Use of safety shoulders as travel lanes.  Toll plazas. Read the entire page →
From page 455... ... 455 required reliability of the estimate and (b) the accuracy with which each observed crash can be associated with an individual site. Read the entire page →
From page 456... ... 456 The Question What is the predicted average crash frequency of the freeway segment for a one-year period? The Facts The study year is 2011. Read the entire page →
From page 457... ... 457 Variable Subscript (a,b) Distance from Segment, Xa,b (mi) Read the entire page →
From page 458... ... 458 Multiple-Vehicle Crashes The SPF for multiple-vehicle fatal-and-injury crashes is calculated from Equation 18-15 and Table 18-5 as follows: [ ] Read the entire page →
From page 459... ... 459 The segment does not have inside barrier, so Pib = 0.0 and the calculation of Wicb does not apply. From Table 18-17, a = -0.00302 for multiple-vehicle fatal-and-injury crashes. Read the entire page →
From page 460... ... 460 The segment does not have shoulder rumble strips. Hence, CMF9, fs, 6, sv, fi and CMF9, fs, 6, sv, pdo are equal to 1.000. Read the entire page →
From page 461... ... 461 Calculation of Predicted Average Crash Frequency The predicted average crash frequency is calculated using Equation 18-2 based on the results obtained in Steps 9 through 11 as follows. Fatal-and-injury crashes: arcrashes/ye971.5 060.2911.3 ,,6,,,,6,,,,6,, = += += fisvfspfimvfspfiatfsp NNN Property-damage-only crashes: arcrashes/ye668.14 099.5569.9 ,,6,,,,6,,,,6,, = += += pdosvfsppdomvfsppdoatfsp NNN Step 12 -- If there is another year to be evaluated in the evaluation period for the selected site, return to Step 8. Read the entire page →
From page 462... ... 462 571.0−=BV Using these computed VK, VA, and VB values, and assuming a calibration factor Csdf, fs+sc of 1.0, the probability of occurrence of a fatal crash is computed using Equation 18-59 as follows: ( ) Read the entire page →
From page 463... ... 463 Worksheets The step-by-step instructions are provided to illustrate the predictive method for calculating the predicted average crash frequency for a freeway segment. To apply the predictive method steps to multiple segments, a series of worksheets are provided for determining the predicted average crash frequency. Read the entire page →
From page 464... ... 464 Table 18-32. Freeway Segment Worksheet (1 of 4) Read the entire page →
From page 465... ... 465 Table 18-33. Freeway Segment Worksheet (2 of 4) Read the entire page →
From page 466... ... 466 Table 18-34. Freeway Segment Worksheet (3 of 4) Read the entire page →
From page 467... ... 467 Table 18-35. Freeway Segment Worksheet (4 of 4) Read the entire page →
From page 468... ... 468  120,000 veh/day  10 percent of AADT volume occurs during high-volume hours  One horizontal curve  2,100-ft equivalent radius  0.25-mi length, entirely in the segment  Curve exists on both roadbeds  12-ft lane width  7-ft outside shoulder width (paved)  6-ft inside shoulder width (paved) Read the entire page →
From page 469... ... 469 Variable Subscript (a,b) Distance from Segment, Xa,b (mi) Read the entire page →
From page 470... ... 470 Multiple-Vehicle Crashes The SPF for multiple-vehicle fatal-and-injury crashes is calculated from Equation 18-15 and Table 18-5 as follows: [ ] Read the entire page →
From page 471... ... 471 178.1,,6,,1 =fisvfsCMF 084.1,,6,,1 =pdomvfsCMF 155.1,,6,,1 =pdosvfsCMF Lane Width (CMF2, fs, 6, y, z ) The segment has 12-ft lanes, which is the base condition for the lane width CMF. Read the entire page →
From page 472... ... 472 993.0,,6,,6 =fisvfsCMF 029.1,,6,,6 =pdomvfsCMF 941.0,,6,,6 =pdosvfsCMF Lane Change (CMF7, fs, 6, mv, z ) CMF7, fs, 6, mv, fi is calculated from Equation 18-30 as follows: ( ) Read the entire page →
From page 474... ... 474 Multiple-Vehicle Crashes The CMFs are applied to the multiple-vehicle fatal-and-injury SPF as follows: ( ) Read the entire page →
From page 475... ... 475 arcrashes/ye008.7 858.2150.4 ,,6,,,,6,,,,6,, = += += fisvfspfimvfspfiatfsp NNN Property-damage-only crashes: arcrashes/ye984.16 454.6530.10 ,,6,,,,6,,,,6,, = += += pdosvfsppdomvfsppdoatfsp NNN Step 12 -- If there is another year to be evaluated in the evaluation period for the selected site, return to Step 8. Otherwise, proceed to Step 13. Read the entire page →
From page 477... ... 477  Table 18-36. Freeway Segment Worksheet (1 of 4) Read the entire page →
From page 478... ... 478 Table 18-36. Freeway Segment Worksheet (1 of 4) Read the entire page →
From page 479... ... 479 Table 18-37. Freeway Segment Worksheet (2 of 4) Read the entire page →
From page 480... ... 480 Table 18-38. Freeway Segment Worksheet (3 of 4) Read the entire page →
From page 481... ... 481 Table 18-39. Freeway Segment Worksheet (4 of 4) Read the entire page →
From page 482... ... 482  Freeway mainline data  120,000 veh/day  10 percent of AADT volume occurs during high-volume hours  No horizontal curvature  12-ft lane width  6-ft inside shoulder width (paved)  40-ft median width  No median barrier  Ramp entrance data  6,750 veh/day  On right side of mainline Assumptions  Crash type distributions used are the default values presented in Table 18-10. Read the entire page →
From page 485... ... 485 Calculation of Predicted Average Crash Frequency The predicted average crash frequency is calculated using Equation 18-2 based on the results obtained in Steps 9 through 11 as follows. Fatal-and-injury crashes: arcrashes/ye505.0 00.1505.0 ,,6,,,,6,* Read the entire page →
From page 486... ... 486 571.0−=BV Using these computed VK, VA, and VB values, and assuming a calibration factor Csdf, fs+sc of 1.0, the probability of occurrence of a fatal crash is computed using Equation 18-59 as follows: ( ) Read the entire page →
From page 487... ... 487 Worksheets The step-by-step instructions are provided to illustrate the predictive method for calculating the predicted average crash frequency for a freeway segment. To apply the predictive method steps to multiple segments, a series of worksheets are provided for determining the predicted average crash frequency. Read the entire page →
From page 488... ... 488 Table 18-40. Freeway Speed-Change Lane Worksheet (1 of 3) Read the entire page →
From page 489... ... 489 Table 18-41. Freeway Speed-Change Lane Worksheet (2 of 3) Read the entire page →
From page 490... ... 490 Table 18-42. Freeway Speed-Change Lane Worksheet (3 of 3) Read the entire page →
From page 491... ... 491  10 percent of AADT volume occurs during high-volume hours  No horizontal curvature  12-ft lane width  6-ft inside shoulder width (paved)  40-ft median width  No median barrier  Ramp exit data  On right side of mainline Assumptions  Crash type distributions used are the default values presented in Table 18-12. Read the entire page →
From page 492... ... 492 arcrashes/ye752.0,,6,, =pdoatEXscspfN Step 10 – Multiply the result obtained in Step 9 by the appropriate CMFs. Each CMF used in the calculation of the predicted average crash frequency of the speed-change lane is calculated in this step. Read the entire page →
From page 493... ... 493 029.1,,6,,6 =pdoatEXscCMF Ramp Exit (CMF13, sc, 6EX, at, z ) CMF13, sc, 6EX, at, fi is calculated from Equation 18-47 as follows:       +×= ex leftfiatEXsc L bIaCMF exp,,6,,13 The ramp entrance connects to the right side of the freeway mainline. Read the entire page →
From page 494... ... 494 arcrashes/ye342.0 00.1342.0 ,,6,,,,6,* ,,,6,, = ×= ×= fiatEXscfsfiatEXscspffiatEXscp CNN Property-damage-only crashes: arcrashes/ye820.0 00.1820.0 ,,6,,,,6,* Read the entire page →
From page 496... ... 496  Table 18-44. Freeway Speed-Change Lane Worksheet (2 of 3) Read the entire page →
From page 497... ... 497 Table 18-43. Freeway Speed-Change Lane Worksheet (1 of 3) Read the entire page →
From page 498... ... 498 Table 18-44. Freeway Speed-Change Lane Worksheet (2 of 3) Read the entire page →
From page 499... ... 499 Table 18-45. Freeway Speed-Change Lane Worksheet (3 of 3) Read the entire page →
From page 500... ... 500  2 freeway segments -- segment 1 (tangent) , segment 2 (curved) Read the entire page →
From page 501... ... 501 076.0 75.06.17 0.1 ,,6, =× =fimvfsk The predicted average fatal-and-injury multiple-vehicle crash frequency Np, fs, 6, mv, fi was computed as 3.911 crashes/year in Sample Problem 1. The weighted adjustment factor wfs, 6, mv, fi is computed as follows: [ ] Read the entire page →
From page 502... ... 502  Table 18-49. Freeway Segment Worksheet (4 of 4) Read the entire page →
From page 503... ... 503 Table 18-46. Freeway Segment Worksheet (1 of 4) Read the entire page →
From page 504... ... 504 Table 18-47. Freeway Segment Worksheet (2 of 4) Read the entire page →
From page 505... ... 505 Table 18-48. Freeway Segment Worksheet (3 of 4) Read the entire page →
From page 506... ... 506 Table 18-49. Freeway Segment Worksheet (4 of 4) Read the entire page →
From page 507... ... 507 The Facts The study year is 2011. The conditions present during this year are provided in the following list. Read the entire page →
From page 508... ... 508  All property-damage-only crashes: Np, aS, ac, at, pdo, r = 31.651 crashes/year The crash period is two years, and the same AADT volumes were used for the two years. Hence, the predicted numbers of crashes in the crash period are simply double the predicted average crash frequency. Read the entire page →
From page 509... ... 509 Assuming independence: 858.74,,,,0 =pdoatacfsV Assuming perfect correlation: 531.274,,,,1 =pdoatacfsV Step 3 -- Compute the weighted adjustment factor. Two weighted adjustment factors are computed in this step. Read the entire page →
From page 510... ... 510 Step 5 -- Compute the expected average crash frequency. The expected average fatal-and-injury crash frequency for the reference year (2009) Read the entire page →
From page 511... ... 511 Table 18-50 is a summary of the predicted average crash frequencies for segments 1 and 2 that were obtained in Sample Problems 1 and 2. It also contains calculations of the variances of the predicted average crash frequencies. Read the entire page →
From page 512... ... 512 Table 18-51. Project-Level EB Method Worksheet (2 of 2) Read the entire page →
From page 513... ... 513 APPENDIX 18A -- WORKSHEETS FOR PREDICTIVE METHOD FOR FREEWAYS Freeway Segment Worksheet (1 of 4) General Information Location Information Analyst Roadway Agency or company Roadway section Date performed Study year Area type Urban Rural Input Data Crash Data Crash Period Study Year Complete the study year column. Read the entire page →
From page 514... ... 514 Freeway Segment Worksheet (2 of 4) Input Data Roadside Data Crash Period Study Year Complete the study year column. Read the entire page →
From page 515... ... 515 Freeway Segment Worksheet (3 of 4) Crash Modification Factors Fatal and Injury Property Damage Only Complete the study year column. Read the entire page →
From page 516... ... 516 Freeway Segment Worksheet (4 of 4) Expected Average Crash Frequency a Crash Severity Distribution K A B C Total FI PDO Total FI + PDO Proportion by injury level 1.000 Expected average crash freq. Read the entire page →
From page 517... ... 517 Freeway Speed-Change Lane Worksheet (1 of 3) General Information Location Information Analyst Roadway Agency or company Roadway section Date performed Study year Area type Urban Rural Input Data Crash Data Crash Period Study Year Complete the study year column. Read the entire page →
From page 518... ... 518 Freeway Speed-Change Lane Worksheet (2 of 3) Crash Modification Factors Complete the study year column. Read the entire page →
From page 519... ... 519 Freeway Speed-Change Lane Worksheet (3 of 3) Expected Average Crash Frequency a Crash Severity Distribution K A B C Total FI PDO Total FI + PDO Proportion by injury level 1.000 Expected average crash freq. Read the entire page →
From page 520... ... 520 Freeway Barrier Worksheet Input Data Segment length L (mi) Crash period Study year Inside shoulder width Wis (ft) Read the entire page →
From page 521... ... 521 Project-Level EB Method Worksheet (1 of 2) Calculations by Site Crash severity category addressed z FI PDO Site Summary b Total Site type and number a Overdispersion Parameter c (1) Read the entire page →
From page 522... ... 522 Project-Level EB Method Worksheet (2 of 2) Calculations for Project Crash Period Study Year Observed crash count during the crash period N* Read the entire page →

From page 385...

... 385 APPENDIX C: PROPOSED HSM FREEWAYS CHAPTER CHAPTER 18 -- PREDICTIVE METHOD FOR FREEWAYS TABLE OF CONTENTS List of Figures ................................................................................................................................ 387 List of Tables ..................................................................................................................................