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From page 52... ... 52 3 Integrating the HSM in the Project Development Process Program and project decisions are typically based on evaluation of costs, right-of-way, traffic operations, and environmental factors. The HSM provides science-based methods and a reliable approach for quantifying safety impacts in terms of crash frequency and severity, allowing agencies to incorporate it throughout the project development process. Read the entire page →
From page 53... ... 53 3.1 HSM in the Planning Phase 3.1.1 Overview The main goal of system planning is to provide decision-makers with the information needed to make choices about investments in their transportation system. In the planning phase, agencies evaluate the multimodal transportation system and identify priorities, programs, and policies to address long-range transportation needs. Read the entire page →
From page 54... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 54 Figure 21: Available Performance Measures (HSM Table 4-2 [HSM p. Read the entire page →
From page 55... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 55 Analysis Descriptive crash statistics for the selected five roadway segments and five intersections were developed. Information on crash type, crash severity, roadway, and environmental conditions was displayed with bar charts, pie charts, and tabular summaries to gain a better understanding of potential issues. Read the entire page →
From page 56... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 56 TABLE 33 Example Problem 1 – Contributing Factors and Selected Safety Countermeasures Facility Type Crash Type Contributing Factor Safety Countermeasure Selected Location ID Intersection Rear-end High approach speed Install automated speed enforcement 83 Slippery pavement Install high-friction surface treatment 25 Poor visibility of signals Install one traffic signal head per lane and add backplates 68, 25 Install flashing beacons as advance warning 25 Angle Limited sight distance Increase sight distance triangle 17, 25 High approach speed Install automated speed enforcement 46, 17 Poor visibility of signal Install one traffic signal head per lane and add backplates 25 Roadway Segment Roadway departure Poor delineation Install Chevrons on curved segment 105, 81 Excessive speed Install automated speed enforcement 35, 105 Drive inattention Install shoulder rumble strips 52, 72 Slippery pavement Install high-friction surface treatment 81 Step 4: Economic Appraisal Data Requirements • Crash data for selected roadway segments and intersections • Current and future AADT values • CMFs for all safety countermeasures under consideration • Construction and implementation costs for each countermeasure • Monetary value of crashes by severity • Service life of the countermeasures Analysis The economic appraisal process outlined in this example only considers changes in crash frequency and does not consider project benefits from travel time, environmental impacts, or congestion relief. The method selected for conducting the economic appraisal of this example is the BCR. Read the entire page →
From page 57... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 57 Results and Discussion The benefits and costs for each proposed project and the relevant BCR are listed in Table 34. TABLE 34 Example Problem 1 – Proposed Projects BCR Project Facility ID Benefit Cost BCR Increase triangle sight distance Intersection 17 $34,500 $9,000 3.8 Intersection 25 $32,000 $11,000 2.9 Install one traffic signal head per lane and add backplates Intersection 68 $26,300 $7,800 3.4 Intersection 25 $28,650 $6,900 4.2 Install flashing beacons as advanced warning Intersection 25 $30,750 $10,600 2.9 Install Chevrons Roadway segment 105 $200,500/mile $80,700/mile 2.5 Roadway segment 81-1 $180,650/mile $59,800/mile 3.0 Install shoulder rumble strips Roadway segment 72 $90,800/mile $38,500/mile 2.4 Roadway segment 52 $102,500/mile $42,980/mile 2.4 Install high-friction surface treatment Roadway segment 81-2 $250,200/mile $190,080/mile 1.3 Intersection 25 $85,650 $59,000 1.5 Install automated speed enforcement Intersection 83 $57,000 $25,000 2.3 Intersection 46 $63,000 $27,500 2.5 Intersection 17 $72,000 $26,000 2.9 Roadway segment 35 $87,000 $23,000 3.5 Roadway segment 105 $92,000 $29,000 3.7 Step 5: Prioritize Projects Data Requirements No additional data are required for selecting the proper safety countermeasures. Read the entire page →
From page 58... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 58 TABLE 35 Example Problem 1 – Incremental BCR Analysis Comparison Project Project ID PVbenefits PVcosts BCR Incremental BCR Preferred Project 1 Install one traffic signal head per lane and add backplates Int 25 $28,650 $6,900 4.15 (2.61) Int 25 Install one traffic signal head per lane and add backplates Int 68 $26,300 $7,800 3.37 2 Install one traffic signal head per lane and add backplates Int 25 $28,650 $6,900 4.15 2.79 Int 17 Increase triangle sight distance Int 17 $34,500 $9,000 3.83 3 Increase triangle sight distance Int 17 $34,500 $9,000 3.83 (2.34) Read the entire page →
From page 59... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 59 TABLE 35 Example Problem 1 – Incremental BCR Analysis Comparison Project Project ID PVbenefits PVcosts BCR Incremental BCR Preferred Project 10 Install automated speed enforcement Seg 35 $87,000 $23,000 3.48 0.25 Seg 35 Install shoulder rumble strips Seg 72 $90,800 $38,500 2.36 11 Install automated speed enforcement Seg 35 $87,000 $23,000 3.48 0.78 Seg 35 Install shoulder rumble strips Seg 52 $102,500 $42,980 2.38 12 Install automated speed enforcement Seg 35 $87,000 $23,000 3.48 (0.04) Seg 35 Install high-friction surface treatment Int 25 $85,650 $59,000 1.45 13 Install automated speed enforcement Seg 35 $87,000 $23,000 3.48 2.54 Seg 81 Install Chevrons Seg 81 $180,650 $59,800 3.02 14 Install Chevrons Seg 81 $180,650 $59,800 3.02 0.95 Seg 81 Install Chevrons Seg 105 $200,500 $80,700 2.48 15 Install Chevrons Seg 81 $180,650 $59,800 3.02 0.53 Seg 81 Install high-friction surface treatment Seg 81 $250,200 $190,080 1.32 Notes: Int = intersection PV = present value Seg = roadway segment The process is repeated to assign priorities to the remaining projects. Read the entire page →
From page 60... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 60 TABLE 36 Example Problem 1 – Ranking Results of Incremental BCR Analysis Rank Project ID Project 6 Roadway segment 52 Install shoulder rumble strips 7 Roadway segment 72 Install shoulder rumble strips 8 Intersection 17 Install automated speed enforcement 9 Intersection 46 Install automated speed enforcement 10 Intersection 83 Install automated speed enforcement 11 Intersection 25 Install high-friction surface treatment 12 Intersection 17 Increase triangle sight distance 13 Intersection 25 Install one traffic signal head per lane and add backplates 14 Intersection 25 Increase triangle sight distance 15 Intersection 25 Install flashing beacons as advanced warning 16 Intersection 68 Install one traffic signal head per lane and add backplates Step 6: Safety Effectiveness Evaluation Data Requirements • Minimum of 10 sites at which the treatment has been implemented • Minimum of 3 years of crash data and traffic volume for the period before implementation • Minimum of 3 years of crash data and traffic volume for the period after implementation • Safety performance function for the facility types being evaluated Analysis An EB before/after safety evaluation method was conducted for the safety effectiveness evaluation. The county DOT decided to upgrade all its signalized intersections to one signal head per travel lane. Read the entire page →
From page 61... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 61 in the after period without treatment. A similar example that can be used as a reference can be found in HSM Section 9.10. Read the entire page →
From page 62... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 62 Figure 22: SR Rural Two-Lane, Two-Way Road Results from the crash analysis indicate a high proportion of head-on, sideswipe-opposing, and fixedobject crashes along the roadway, particularly in the curve. A high proportion of angle crashes have also occurred at the intersections. Read the entire page →
From page 63... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 63 After reviewing this example, the user should be able to: • Understand what input data are required and the assumptions that are commonly made regarding default values for the HSM procedures • Calculate the predicted and expected crash frequency of rural two-lane two-way road intersections and roadway segments using the HSM • Calculate the predicted crash frequency of rural multilane intersections and segments using the HSM • Understand how to reasonably interpret the results from an HSM analysis, and how these results can be used to support a particular decision • Understand the limitations of the HSM procedures and when it is appropriate to use other models or computational tools 3.2.3 Part 1 – Rural Two-Lane Two-Way Roads Data Requirements for Part 1 The sample corridor was divided into three roadway segment sections (two tangents and one curve) , as shown in Figure 23. Read the entire page →
From page 64... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 64 TABLE 37 Example Problem 2 – Intersections Input Data Intersection Characteristics Input Data Intersection 1 Intersection 2 Intersection 3 Number of signalized or uncontrolled approaches with a right-turn lane 0 0 0 Intersection lighting Not present Not present Not present Calibration factor (Ci) 1.17 1.17 1.17 Observed crash data (crashes/year) Read the entire page →
From page 65... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 65 Analysis The rural two-lane, two-way predictive method for intersections and roadway segments under existing conditions (year 2012) was applied in the following subsections. Read the entire page →
From page 66... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 66 The combined CMF is calculated by multiplying all the intersection CMFs: 𝐶𝑀𝐹 =𝐶𝑀𝐹 × 𝐶𝑀𝐹 × 𝐶𝑀𝐹 × 𝐶𝑀𝐹 𝐶𝑀𝐹 = 1.06 × 1.00 × 1.00 × 1.00 𝐶𝑀𝐹 = 1.06 Apply Calibration Factor The next step is to multiply the results obtained above by the appropriate calibration factor. For this example, the calibration factor for stop-controlled three-leg intersections has been assumed to be 1.17. Read the entire page →
From page 67... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 67 The average predicted crash frequency for Intersection 3 is obtained by the arithmetic average of the annual predicted crash frequencies (Npredicted int) Read the entire page →
From page 68... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 68 Horizontal Curve (CMF3r) For this example, the length of curve is 0.8 mile with a radius of curvature of 2,650 feet and no spiral transitions. Read the entire page →
From page 69... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 69 Automated Speed Enforcement (CMF12r) The example roadway segment does not have automated speed enforcement available; therefore, a CMF of 1.00 is applied. Read the entire page →
From page 70... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 70 TABLE 40 Example Problem 2 – Roadway Segment 2 Multiyear Analysis Results Roadway Segment 2 Year 2008 2009 2010 2011 2012 CMFcomb 1.527 1.527 1.527 1.527 1.527 Ci 1.30 1.30 1.30 1.30 1.30 Npredicted seg 3.44 3.51 3.58 3.65 3.72 Notes: CMFcomb = combined CMF Nspf = predicted average crash frequency estimated for base conditions Npredicted seg = predicted average crash frequency for the roadway segment The average predicted crash frequency for Roadway Segment 2 is obtained through the arithmetic average of the annual predicted crash frequencies (Npredicted seg) Read the entire page →
From page 71... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 71 Empirical Bayes Adjustment Method The next step in the process is to update predictions based on the observed/reported crashes. A total of 62 roadway segment crashes and 11 intersection crashes occur each year. Read the entire page →
From page 72... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 72 For this example, there were an average of 40 observed/reported crashes per year on Roadway Segment 2 and an average of 2 observed/reported crashes per year at Intersection 3. The expected number of crashes for roadway segments and intersections is then calculated as follows: 𝑁 = 𝑤 × 𝑁 + (1 − 𝑤) Read the entire page →
From page 73... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 73 TABLE 42 Example Problem 2 – Predicted and Expected Crash Frequency Calculations Summary (2008 to 2012) Site Type Predicted Average Crash Frequency (crashes/year) Read the entire page →
From page 74... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 74 Alternatives Analysis The previous section demonstrated the application of the predictive method for rural two-lane, two-way roadway segments and intersections under existing conditions. The predictive method can also be applied to alternatives analysis. Read the entire page →
From page 75... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 75 TABLE 43 Example Problem 2 – Roadway Segment Alternatives Input Data Roadway Segment 3 Characteristics Input Data by Alternative No Build Alternative 1 Alternative 2 Shoulder width (feet) 1 6 6 Roadside hazard rating 5 5 3 Segment lighting Not present Not present Present Auto speed enforcement Not present Not present Present TABLE 44 Example Problem 2 – Intersection Alternatives Input Data Intersection 1 Characteristics Input Data by Alternative No Build Alternative 1 Alternative 2 Number of signalized or uncontrolled approaches with a left-turn lane 0 1 1 Intersection lighting Not present Not present Present Intersection 2 Characteristics Input Data by Alternative No Build Alternative 1 Alternative 2 Number of signalized or uncontrolled approaches with a left-turn lane 0 1 1 Intersection lighting Not present Not present Present Intersection 3 Characteristics Input Data by Alternative No Build Alternative 1 Alternative 2 Number of signalized or uncontrolled approaches with a left-turn lane 0 1 1 Intersection lighting Not present Not present Present The effect of the multiple treatments (such as widening shoulders, lighting the roadway segments and intersections, adding left-turn lanes) Read the entire page →
From page 76... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 76 calculations are provided in the sample spreadsheets provided with the Highway Safety Manual User Guide. TABLE 45 Example Problem 2 – Alternatives Analysis Results Summary Alternative Site Type Npredicted Nobserved Overdispersion Parameter (k) Read the entire page →
From page 77... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 77 Data Requirements for Part 2 Figure 24 shows the different facility types included in this example. Since the rural multilane predictive method does not include a CMF for curves, there is no need to break the corridor into multiple segments. Read the entire page →
From page 78... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 78 TABLE 47 Example Problem 2 – Roadway Segment 1 Input Data Characteristics Input Data Roadway Segment 1 Roadway type Divided Segment length (miles) 3.90 Traffic volume (vpd) Read the entire page →
From page 81... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 81 Roadway Segments Roadway segment data required to apply the predictive method are summarized in Table 47. For this example, the analysis corridor consists of only one four-lane divided segment. Read the entire page →
From page 82... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 82 Automated Speed Enforcement (CMF5r) The example segment does not have automated speed enforcement available; therefore, a CMF of 1.00 is applied. Read the entire page →
From page 83... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 83 TABLE 49 Example Problem 2 – Roadway Segment 1 Multiyear Analysis Results Roadway Segment 1 Year 2008 2009 2010 2011 2012 CMF2ru 1.00 1.00 1.00 1.00 1.00 CMF3ru 1.00 1.00 1.00 1.00 1.00 CMF4ru 1.00 1.00 1.00 1.00 1.00 CMF5ru 1.00 1.00 1.00 1.00 1.00 CMFcomb 1.00 1.00 1.00 1.00 1.00 Cr 1.08 1.08 1.08 1.08 1.08 Npredicted seg 6.56 6.70 6.84 6.98 7.13 Corridor Analysis (Intersections and Roadway Segments) Analysis results for intersections and roadway segments can be combined into a corridor analysis. Read the entire page →
From page 84... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 84 the EB method. Since this project upgrade involves the development of a new alignment for a substantial portion of the project length, the EB method is not applicable. Read the entire page →
From page 85... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 85 TABLE 52 Example Problem 2 – Future Conditions Alternative Analysis Summary (2030) Alternative Site Type Npredicted Total Npredicted FI Npredicted PDO Rural Two-lane: No Build Segment 1 7.71 2.47 5.23 Segment 2 5.58 1.79 3.79 Segment 3 12.85 4.12 8.72 Intersection 1 6.31 2.62 3.69 Intersection 2 6.90 2.87 4.04 Intersection 3 4.68 1.94 2.74 Total 44.04 15.82 28.22 Rural Two-Lane: Alternative 1 Segment 1 6.27 2.01 4.26 Segment 2 4.54 1.46 3.08 Segment 3 10.45 3.35 7.10 Intersection 1 3.54 1.47 2.07 Intersection 2 3.87 1.60 2.26 Intersection 3 2.62 1.09 1.53 Total 31.28 10.98 20.30 Rural Two Lane: Alternative 2 Segment 1 4.70 1.51 3.19 Segment 2 3.41 1.09 2.31 Segment 3 7.84 2.52 5.32 Intersection 1 3.19 1.32 1.86 Intersection 2 3.48 1.45 2.04 Intersection 3 2.36 0.98 1.38 Total 24.98 8.87 16.11 Rural Multilane: Alternative 3 Segment 1 10.91 5.54 5.37 Intersection 1 1.37 0.46 0.91 Intersection 2 2.98 1.40 1.58 Intersection 3 2.87 1.45 1.43 Total 18.14 8.84 9.29 Results and Discussion From Part 1 of the problem, it was concluded that the proposed countermeasures for rural two-lane Alternative 2 produced the lower predicted and expected crash frequency. Read the entire page →
From page 86... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 86 The state DOT also considered modifying the rural two-lane corridor to a four-lane divided facility. The analysis was conducted for future conditions (design year 2030) Read the entire page →
From page 87... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 87 Objectives This example is focused on evaluating the crash reduction potential of various design alternatives for an urban arterial. Several improvements were considered as part of the project, including providing a physical median along the corridor in one section of the corridor, providing dedicated bus pullout areas, widening the sidewalk, and providing a median separation. Read the entire page →
From page 88... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 88 TABLE 53 Example Problem 3 – Intersections Input Data Characteristics Input Data Intersection 1 Intersection 2 Number of approaches with right-turn lanes 0 − Number of approaches with left-turn signal phasing 0 − Type of left-turn phasing Not applicable − Number of approaches with right-turn-on-red prohibited Not present − Intersection red-light cameras Not present − Sum of all pedestrian crossing volumes 400 − Maximum number of lanes crossed by a pedestrian 5 − Number of bus stops within 1,000 feet (300 meters) of the intersection 1 − Schools within 1,000 feet (300 meters) Read the entire page →
From page 89... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 89 Roadway Segment Data TABLE 55 Example Problem 3 – Arterial Roadway Segment Input Data Characteristics Input Data Roadway Segment 1 Roadway type 5T Segment length (miles) 0.3 Traffic volume (vpd) Read the entire page →
From page 90... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 90 Analysis The urban and suburban arterial safety analysis differs from the previous two predictive methods since pedestrian and bicycle collisions must be accounted for, with respect to intersections and roadway segments. Each collision type will be analyzed in detail. Read the entire page →
From page 91... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 91 Single-Vehicle Collisions by Severity Level for Intersection 1 𝑁 = 𝑒𝑥𝑝 −10.21 + 0.68 × 𝑙𝑛(23,000) Read the entire page →
From page 92... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 92 Before calculating the vehicle-bicycle collisions, the predicted average crash frequency of multiple- and single-vehicle crashes must be calculated: 𝑁 = 𝑁 + 𝑁 𝑁 = 7.04 + 0.45 = 7.49 Apply HSM Part C Crash Modification Factors to Multiple- and Single-Vehicle Collisions CMFs are applied to adjust the estimated crash frequencies for base conditions to account for the effect of site-specific geometry and traffic features. Intersection Left-Turn Lanes (CMF1i) Read the entire page →
From page 93... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 93 Apply Part C Crash Modification Factors for Vehicle-Pedestrian and Vehicle-Bicycle Collisions at Signalized Intersections Vehicle-Pedestrian Collisions at Signalized Intersections Bus Stops (CMF1p) Intersection 1 has a bus stop within 1,000 feet. Read the entire page →
From page 94... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 94 Single-Vehicle Collisions by Severity Level for Intersection 1 𝑁 = 0.45 𝑐𝑟𝑎𝑠ℎ𝑒𝑠𝑦𝑒𝑎𝑟 𝑁 ( ) Read the entire page →
From page 95... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 95 TABLE 57 Example Problem 3 – Intersection 1 Multiyear Analysis Results Intersection 1 Year 2008 2009 2010 2011 2012 AADTmajor 21,248 21,673 22,107 22,549 23,000 AADTminor 12,934 13,193 13,456 13,725 14,000 Crashes/year 3 7 4 7 4 Nbrmv 6.354 6.520 6.690 6.860 7.040 Nbrsv 0.416 0.420 0.430 0.440 0.450 Npedbase 0.075 0.076 0.076 0.077 0.078 Npedi 0.234 0.236 0.238 0.240 0.242 Nbikei 0.102 0.104 0.107 0.110 0.112 CMF1i 4SG 1.00 1.00 1.00 1.00 1.00 CMF2i 4SG 1.00 1.00 1.00 1.00 1.00 CMF3i 4SG 1.00 1.00 1.00 1.00 1.00 CMF4i 4SG 1.00 1.00 1.00 1.00 1.00 CMF5i 4SG 1.00 1.00 1.00 1.00 1.00 CMF6i 4SG 1.00 1.00 1.00 1.00 1.00 CMFcomb 1.00 1.00 1.00 1.00 1.00 CMF1p 2.78 2.78 2.78 2.78 2.78 CMF2p 1.00 1.00 1.00 1.00 1.00 CMF3p 1.12 1.12 1.12 1.12 1.12 CMFped comb 3.11 3.11 3.11 3.11 3.11 Ci 1.15 1.15 1.15 1.15 1.15 Npredicted int 8.171 8.376 8.586 8.801 9.022 The average predicted crash frequency for Intersection 1 is obtained by adding the arithmetic 5-year average of multiple- and single-vehicle, vehicle-pedestrian, and vehicle-bicycle annual predicted crash frequencies. For this example, this value is 8.59 crashes per year. Read the entire page →
From page 96... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 96 The general functional form of the roadway segment multiple- and single-vehicle collision SPFs, excluding the driveway-related SPF (HSM Equation 12-16 [HSM p. Read the entire page →
From page 97... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 97 Single-Vehicle Collisions by Severity 𝑁 ( ) Read the entire page →
From page 98... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 98 Roadside Fixed Objects (CMF2r) For this CMF, HSM Equation 12-33 (HSM p. Read the entire page →
From page 99... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 99 Multiple-Vehicle Driveway-Related Collisions by Severity 𝑁 = 1.30 𝑐𝑟𝑎𝑠ℎ𝑒𝑠𝑦𝑒𝑎𝑟 𝑁 ( ) Read the entire page →
From page 100... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 100 NOTE: These factors apply to the methodology for predicting all severity levels combined. All results obtained by applying these pedestrian and bicycle adjustment factors are treated as fatal-and-injury crashes. Read the entire page →
From page 101... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 101 The average predicted crash frequency for the study segment is obtained by adding the arithmetic 5-year average of multiple- and single-vehicle, multiple-vehicle driveway-related, vehicle-pedestrian, and vehicle-bicycle annual predicted crash frequencies. For this example, this value is 5.57 crashes per year. Read the entire page →
From page 102... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 102 TABLE 60 Example Problem 3 – Disaggregated Roadway Segment and Intersection Crash Data for the Study Period (2008 to 2012) Collision Type Intersection 1 2008 2009 2010 2011 2012 Sum Average Multiple-Vehicle Nondriveway 3 6 4 7 4 24 4.8 Single-Vehicle 0 1 0 0 0 1 0.2 Total 3 7 4 7 4 25 5 Collision Type Intersection 2 2008 2009 2010 2011 2012 Sum Average Multiple-Vehicle Nondriveway 2 6 5 3 4 20 4 Single-Vehicle 0 0 0 0 0 0 0 Total 2 6 5 3 4 20 4 Collision Type Roadway Segment 2008 2009 2010 2011 2012 Sum Average Multiple-Vehicle Nondriveway 5 7 6 8 9 35 7 Single-Vehicle 0 2 1 1 1 5 1 Multiple-Vehicle Driveway-Related 6 5 3 4 2 20 4 Total 11 14 10 13 12 60 12 There were 60 roadway segment crashes and 45 intersection crashes for the study period. Read the entire page →
From page 103... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 103 parameter for this collision type is 0.81, and the sum of all the predicted roadway segment crashes is 14.96: 𝑤 = 11 + 0.81 × (2.86 + 2.92 + 2.99 + 3.06 + 3.13) = 0.076 The segment predicted average crash frequency for this collision type is 2.99 crashes per year. Read the entire page →
From page 104... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 104 absence of observed/reported pedestrian and bicycle crashes, the total and fatal-and-injury (not applicable to PDO) predicted crash frequencies for roadway segments and intersections are calculated by adding the multiple-vehicle and single-vehicle crashes to the pedestrian and bicycle predicted crashes. Read the entire page →
From page 105... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 105 No Build. The facility is an urban arterial with commercial development. Read the entire page →
From page 106... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 106 TABLE 64 Example Problem 3 – Intersection Alternatives Input Data Characteristics Input Data by Alternative No Build Alternative 1 Alternative 2 Intersection 1 Intersection type 4SG 4SG 4SG Intersection lighting Not present Present Present Data for Signalized Intersections Only Number of approaches with left-turn lanes 0 2 4 Number of approaches with left-turn signal phasing 0 2 4 Type of left-turn signal phasing for leg 1 Protected/ Permitted Protected Type of left-turn signal phasing for leg 2 Protected/ Permitted Protected Type of left-turn signal phasing for leg 3 Protected/ Permitted Type of left-turn signal phasing for leg 4 (if applicable) Protected/ Permitted Maximum number of lanes crossed by a pedestrian 5 5 7 Intersection 2 Intersection type 3ST 3ST 3ST Intersection lighting Not present Present Present Data for Unsignalized Intersections Only -- -- -- Number of major-road approaches with left-turn lanes 0 0 2 Number of major-road approaches with right-turn lanes 0 0 1 TABLE 65 Example Problem 3 – Roadway Segments Alternatives Input Data Segment Characteristics Input Data by Alternative No Build Alternative 1 Alternative 2 Roadway type 5T 5T 4D Type of on-street parking Parallel (Commercial/ Industrial) Read the entire page →
From page 107... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 107 These safety improvements are all considered by the application of CMFs, which are used to adjust the SPF base condition estimate of predicted average crash frequency for the effect of the individual geometric design and traffic control features. The CMF for the SPF base condition of each geometric design or traffic control feature has a value of 1.00. Read the entire page →
From page 108... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 108 most cost-effective. Refer to HSM Chapter 7, Economic Appraisal, for methods to compare the benefits of potential safety countermeasures to crash costs. Read the entire page →
From page 109... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 109 Data Requirements Roadway Segment Data Table 67 contains the input data for this analysis. TABLE 67 Example Problem 4 – Curve Segments Input Data Characteristics Input Data Roadway Segment 1 Roadway Segment 2 Segment length (feet) Read the entire page →
From page 110... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 110 also upgraded. All remaining parameters are the same for both locations. Read the entire page →
From page 111... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 111 Horizontal Curve (CMF3r) For this example, Roadway Segment 1 length is 0.24 mile with a radius of curvature of 1,600 feet, and Roadway Segment 2 length is 0.30 mile with a radius of curvature of 2,000 feet. Read the entire page →
From page 112... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 112 Roadside Design (CMF10r) The data in this example indicate a RHR of 4 for Roadway Segment 1, and a rating of 3 for Roadway Segment 2. Read the entire page →
From page 113... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 113 TABLE 68 Example Problem 4 – Roadway Segment 1 Multiyear Analysis Results Roadway Segment 1 Year 2008 2009 2010 2011 2012 AADT 12,719 12,910 13,104 13,300 13,500 Nspf 0.816 0.828 0.84 0.853 0.866 CMF1r 1.00 1.00 1.00 1.00 1.00 CMF2r 1.18 1.18 1.18 1.18 1.18 CMF3r 1.13 1.13 1.13 1.13 1.13 CMF4r 1.06 1.06 1.06 1.06 1.06 CMF5r 1.00 1.00 1.00 1.00 1.00 CMF6r 1.00 1.00 1.00 1.00 1.00 CMF7r 1.00 1.00 1.00 1.00 1.00 CMF8r 1.00 1.00 1.00 1.00 1.00 CMF9r 1.00 1.00 1.00 1.00 1.00 CMF10r 1.07 1.07 1.07 1.07 1.07 CMF11r 1.00 1.00 1.00 1.00 1.00 CMF12r 1.00 1.00 1.00 1.00 1.00 CMFcomb 1.52 1.52 1.52 1.52 1.52 Cr 1.23 1.23 1.23 1.23 1.23 Npredicted seg 1.52 1.54 1.57 1.59 1.62 TABLE 69 Example Problem 4 – Roadway Segment 2 Multiyear Analysis Results Roadway Segment 2 Year 2008 2009 2010 2011 2012 AADT 12,719 12,910 13,104 13,300 13,500 Nspf 1.019 1.035 1.050 1.066 1.082 CMF1r 1.00 1.00 1.00 1.00 1.00 CMF2r 1.00 1.00 1.00 1.00 1.00 CMF3r 1.09 1.09 1.09 1.09 1.09 CMF4r 1.00 1.00 1.00 1.00 1.00 CMF5r 1.00 1.00 1.00 1.00 1.00 CMF6r 1.00 1.00 1.00 1.00 1.00 CMF7r 1.00 1.00 1.00 1.00 1.00 CMF8r 1.00 1.00 1.00 1.00 1.00 Read the entire page →
From page 114... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 114 TABLE 69 Example Problem 4 – Roadway Segment 2 Multiyear Analysis Results Roadway Segment 2 Year 2008 2009 2010 2011 2012 CMF9r 1.00 1.00 1.00 1.00 1.00 CMF10r 1.00 1.00 1.00 1.00 1.00 CMF11r 1.00 1.00 1.00 1.00 1.00 CMF12r 1.00 1.00 1.00 1.00 1.00 CMFcomb 1.09 1.09 1.09 1.09 1.09 Cr 1.23 1.23 1.23 1.23 1.23 Npredicted seg 1.36 1.38 1.40 1.42 1.45 The average predicted crash frequency for Roadway Segments 1 and 2 are obtained through the arithmetic average of the annual predicted crash frequencies (Npredicted seg) Read the entire page →
From page 115... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 115 For this calculation, the overdispersion parameter from each of the applied SPFs is needed. The overdispersion parameter for Roadway Segment 1 is 0.983 and for Roadway Segment 2 is 0.787. Read the entire page →
From page 116... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 116 TABLE 70 Example Problem 4 – Predicted, Expected, and Observed Crash Frequency Calculations Summary (2008 to 2012) Site Type Predicted Average Crash Frequency (crashes/year) Read the entire page →
From page 117... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 117 TABLE 71 Example Problem 4 – Predicted, Expected, and Observed Crash Frequency Calculations Summary for the Three Scenarios (2008 to 2012) Site Type Predicted Average Crash Frequency (crashes/year) Read the entire page →
From page 118... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 118 Results and Discussion The application of the HSM in the design stage provides engineers with valuable information in the decision-making process. NOTE: The HSM does not require agencies to implement specific alternatives based solely on safety performance evaluation but instead provides the means to make an informed decision. Read the entire page →
From page 119... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 119 • Understand how to reasonably interpret the results from an HSM analysis, and how these results can be used to support a particular decision Data Requirements The existing skew angle is 40 degrees. The expected average crash frequency for this site is 12 crashes per year. Read the entire page →
From page 120... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 120 3.3.4 Example Problem 6: Deceleration Ramp Lengthening Introduction As part of a rehabilitation project, a local jurisdiction is considering to make improvements to an urban grade-separated diamond interchange. One of the improvements is the lengthening of an existing eastbound off-ramp deceleration lane. Read the entire page →
From page 121... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 121 An MSE value of 2 yields a 95-percent probability that the true value is between 15.39 and 19.95 crashes per year. The change in average crash frequency is calculated as follows: 𝐿𝑜𝑤 𝐸𝑠𝑡𝑖𝑚𝑎𝑡𝑒 = 19.95 − 19.00 = 0.95 𝑖𝑛𝑐𝑟𝑒𝑎𝑠𝑒 𝐻𝑖𝑔ℎ 𝐸𝑠𝑡𝑖𝑚𝑎𝑡𝑒 = 19.00 − 15.39 = 3.61 𝑑𝑒𝑐𝑟𝑒𝑎𝑠𝑒 Results and Discussion The range of values suggests that lengthening the deceleration ramp by 350 feet may potentially increase, decrease, or cause no change in the average crash frequency at the study location. Read the entire page →
From page 122... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 122 Data Requirements The signalized intersection expected average crash frequency is 28 crashes per year. The intersection has four permissive left-turn phases, and the improvement considers upgrading the major movement approaches to protected left turn. Read the entire page →
From page 123... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 123 The HSM provides two work zone CMFs that take into account work zone length and duration. Although more information is needed for a comprehensive work design, the following example is intended to illustrate the use of such CMFs and illustrate how maintenance of traffic (MOT) Read the entire page →
From page 124... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 124 𝐶𝑀𝐹 = 1 + 463 × 1.11100 = 6.13 𝐶𝑀𝐹 = 1 + 650 × 1.11100 = 8.22 Next, calculate the combined effect of work zone length and duration under the proposed work zone condition: 𝐶𝑀𝐹 = 𝐶𝑀𝐹 × 𝐶𝑀𝐹 𝐶𝑀𝐹 = 6.90 × 4.05 = 27.96 𝐶𝑀𝐹 = 3.61 × 6.13 = 22.17 𝐶𝑀𝐹 = 1.64 × 8.22 = 13.50 This result is used to quantify the expected number of crashes under the proposed work zone scenario: 𝐸𝑥𝑝𝑒𝑐𝑡𝑒𝑑 𝑐𝑟𝑎𝑠ℎ𝑒𝑠 𝑆𝑐𝑒𝑛𝑎𝑟𝑖𝑜 1 \| = 27.96 × 4 = 111.8 𝑐𝑟𝑎𝑠ℎ𝑒𝑠𝑦𝑒𝑎𝑟 𝐸𝑥𝑝𝑒𝑐𝑡𝑒𝑑 𝑐𝑟𝑎𝑠ℎ𝑒𝑠 𝑆𝑐𝑒𝑛𝑎𝑟𝑖𝑜 2 . \| = 22.17 × 4 = 88.7 𝑐𝑟𝑎𝑠ℎ𝑒𝑠𝑦𝑒𝑎𝑟 𝐸𝑥𝑝𝑒𝑐𝑡𝑒𝑑 𝑐𝑟𝑎𝑠ℎ𝑒𝑠 𝑆𝑐𝑒𝑛𝑎𝑟𝑖𝑜 3 \| = 13.5 × 4 = 54.0 𝑐𝑟𝑎𝑠ℎ𝑒𝑠𝑦𝑒𝑎𝑟 Lastly, the change in expected crash frequency under the proposed work zone scheme is calculated as follows: 𝐶ℎ𝑎𝑛𝑔𝑒 𝑒𝑥𝑝𝑒𝑐𝑡𝑒𝑑 𝑐𝑟𝑎𝑠ℎ𝑒𝑠 𝑆𝑐𝑒𝑛𝑎𝑟𝑖𝑜 1 = 111.8 − 4.0 = 107.8 𝑐𝑟𝑎𝑠ℎ𝑒𝑠𝑦𝑒𝑎𝑟 𝑖𝑛𝑐𝑟𝑒𝑎𝑠𝑒 𝐶ℎ𝑎𝑛𝑔𝑒 𝑒𝑥𝑝𝑒𝑐𝑡𝑒𝑑 𝑐𝑟𝑎𝑠ℎ𝑒𝑠 𝑆𝑐𝑒𝑛𝑎𝑟𝑖𝑜 2 = 88.7 − 4.0 = 84.7 𝑐𝑟𝑎𝑠ℎ𝑒𝑠𝑦𝑒𝑎𝑟 𝑖𝑛𝑐𝑟𝑒𝑎𝑠𝑒 𝐶ℎ𝑎𝑛𝑔𝑒 𝑒𝑥𝑝𝑒𝑐𝑡𝑒𝑑 𝑐𝑟𝑎𝑠ℎ𝑒𝑠 𝑆𝑐𝑒𝑛𝑎𝑟𝑖𝑜 3 = 54.0 − 4.0 = 50.0 𝑐𝑟𝑎𝑠ℎ𝑒𝑠𝑦𝑒𝑎𝑟 𝑖𝑛𝑐𝑟𝑒𝑎𝑠𝑒 Results and Discussion The work zone example shows how to compute the change in expected average crash frequency for three proposed work zone scenarios. Read the entire page →
From page 125... ... SECTION 4 – PART D: CMF APPLICATIONS GUIDANCE 125 As a result, the combined effect of CMF related to length and duration yields to the lowest increase in the expected annual average crashes. The standard errors for these CMFs were not available; therefore, a confidence interval in the estimate could not be calculated. Read the entire page →

From page 52...

... 52 3 Integrating the HSM in the Project Development Process Program and project decisions are typically based on evaluation of costs, right-of-way, traffic operations, and environmental factors. The HSM provides science-based methods and a reliable approach for quantifying safety impacts in terms of crash frequency and severity, allowing agencies to incorporate it throughout the project development process.