Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects (2021) / Chapter Skim
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Pages 98-124
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From page 98... ...
98 3R Project Design Guidelines for Specific Roadway Types This chapter presents design guidelines for 3R projects. The design guidelines are based on explicit consideration of estimates of the crash reduction effectiveness of design improvements, where available, and on the use of before–after benefit–cost analysis tools.
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From page 99... ...
3R Project Design Guidelines for Specific Roadway Types 99 Lane Widening on Rural Two-Lane Highways Section length 1.000 mi AADT 2,000 veh/day Terrain Level Pavement type Flexible Lane width 9.0 ft Shoulder width 2 ft Shoulder type Unpaved Roadside slope 1V:2H Centerline rumble strip No Shoulder rumble strip No Crash history No Number of curves in roadway section 2 Maximum superelevation rate 8% Design speed 55 mph Horizontal Curve Curve Length (mi) Radius (ft)
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From page 100... ...
100 Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects be noted that the HSM Chapter 10 crash prediction procedures show that the benefit of lane widening from 11 to 12 ft on rural two-lane highways is relatively small (2)
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From page 101... ...
3R Project Design Guidelines for Specific Roadway Types 101 6.1.2.1 Option 1: Conduct a Site-Specific Benefit–Cost Analysis for Each Individual 3R Project The most desirable approach to decisions about cost-effective shoulder widening is to conduct a site-specific benefit–cost analysis for each individual 3R project. Site-specific benefit–cost analyses are desirable because even nominally similar sites may differ in roadway characteristics, traffic volumes, crash history, and improvement costs, such that shoulder widening may be cost-effective at one site and not at another.
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From page 102... ...
102 Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects shoulder widening analogous to those shown in Table 44.
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From page 103... ...
3R Project Design Guidelines for Specific Roadway Types 103 projects, sensitivity analyses with the tool have shown that, because of their high cost, curve realignment improvements are seldom cost-effective. Realignment of multiple horizontal curves on a roadway section would generally be considered as reconstruction and, therefore, out of the scope of 3R improvements.
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From page 104... ...
104 Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects for drainage, the pavement cross slope should be restored to meet the highway agency's applicable design criteria.
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From page 105... ...
3R Project Design Guidelines for Specific Roadway Types 105 and located in accordance with each agency's current practices. Rumble strips are appropriate in most rural locations, except where the noise created by the rumble strips may disturb nearby residents.
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From page 106... ...
106 Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects 6.1.9 Roadside Slope Flattening Roadside slope flattening should be considered for each 3R project on a rural two-lane highway with roadside slopes steeper than 1V:4H where sufficient right-of-way for slope flattening is available (or could be acquired)
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From page 107... ...
3R Project Design Guidelines for Specific Roadway Types 107 There is no option for developing minimum AADT guidelines for roadside slope flattening projects because the costs of such projects can vary widely from site to site, making site-specific cost estimates necessary. Figure 59 presents the results of benefit–cost analysis for roadside slope flattening on a rural two-lane highway.
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From page 108... ...
108 Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects 6.1.11 Installation/Rehabilitation of Guardrail and Other Traffic Barriers Existing guardrail or other traffic barriers that have reached the end of their useful life or are of obsolete design should generally be rehabilitated or replaced as part of a 3R project.
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From page 109... ...
3R Project Design Guidelines for Specific Roadway Types 109 6.2 Rural Multilane Undivided Highways 6.2.1 Lane Widening Lane widening should be considered for each 3R project on a rural multilane undivided highway with existing lane widths of less than 12 ft. Decisions about lane widening for 3R projects should be based on benefit–cost analysis.
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From page 110... ...
110 Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects 3R projects should be based on benefit–cost analysis.
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From page 111... ...
3R Project Design Guidelines for Specific Roadway Types 111 6.2.3 Horizontal Curve Improvements Horizontal curve improvements on rural multilane undivided highways may be considered 3R projects in some cases. Variances in superelevation of greater than 1% on horizontal curves on rural multilane undivided highways should be restored in 3R projects.
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From page 112... ...
112 Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects (lanes and shoulders combined)
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From page 113... ...
3R Project Design Guidelines for Specific Roadway Types 113 that, as a default, highway agencies will restore the pavement markings with the equivalent of the existing pavement markings. Conventional paint is the least-expensive pavement marking material and typically has a service life of 1 to 2 years, depending on traffic volume and climate conditions.
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From page 114... ...
114 Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects breakaway design need to be considered.
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From page 115... ...
3R Project Design Guidelines for Specific Roadway Types 115 only when the analysis indicates that the expected crash reduction benefits will exceed the costs of the improvement or when a crash analysis finds existing crash patterns that can potentially be reduced by lane widening. Where there are no existing crash patterns that can potentially be reduced by lane widening and the expected crash reduction benefits are less than the costs of improvement, lane widening would be a poor investment, and available funds would be better invested at another location where the crash reduction benefits would be greater.
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From page 116... ...
116 Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects available funds would be better invested at another location where the crash reduction benefits would be larger.
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From page 117... ...
3R Project Design Guidelines for Specific Roadway Types 117 crest vertical curves or objects on the inside of horizontal curves. The SSD design criteria used by most states are based on the SSD values in the AASHTO Green Book (4)
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From page 118... ...
118 Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects intended travel lane.
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From page 119... ...
3R Project Design Guidelines for Specific Roadway Types 119 reduction benefits are less than the costs of improvement, roadside slope flattening would be a poor investment, and available funds would be better invested at another location where the crash reduction benefits would be larger. Roadside slope flattening should be considered only where a benefit–cost analysis with the site-specific benefit–cost analysis tool (Spreadsheet Tool 1)
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From page 120... ...
120 Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects 6.3.12 Intersection Turn Lane Improvements The crash reduction effectiveness of intersection turn lane improvements on rural multilane divided nonfreeways is documented in Section 4.3.3.9.
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From page 121... ...
3R Project Design Guidelines for Specific Roadway Types 121 Where the superelevation of an existing curve is less than the design superelevation value in the AASHTO Green Book (4) by more than 1%, restoration of superelevation to the Green Book value should be considered as part of any 3R project conducted.
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From page 122... ...
122 Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects As an alternative to removing roadside objects, consideration may also be given to replacing the object with a similar object of breakaway design, relocating the object behind an existing guardrail or traffic barrier, or installing a new guardrail or traffic barrier.
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From page 123... ...
3R Project Design Guidelines for Specific Roadway Types 123 At locations that were built with outside shoulders less than 12 ft in width, Spreadsheet Tool 1 can be used for benefit–cost evaluation of shoulder-widening alternatives. In such cases, widening to 12-ft shoulders is likely to be cost-effective over the typical range of freeway volumes.
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From page 124... ...
124 Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects 6.5.7 Horizontal Curve Improvements Where the superelevation of an existing curve is less than the design superelevation value in the AASHTO Green Book (4)
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