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60 Chapter 6. 3R Improvement Implementation Costs Many aspects of the roadway geometry can be improved during a 3R project. To understand whether such improvements are cost-effective, it is desirable to perform a cost-effectiveness or benefitâcost analysis of the proposed changes. A benefitâcost ratio is a metric that can be used to determine if roadway countermeasures are cost-effective. The previous chapter discussed the crash reduction effectiveness of roadway improvements. This chapter describes the process of determining the costs of these improvements. These costs are referred to in this report as implementation costs, rather than construction costs, because they can include the cost of right- of-way acquisition as well as construction. A cost estimation procedure has been developed for use as a default in benefitâcost analyses to quantify the cost of implementing specific improvements as part of a 3R project. This procedure combines the cost of cross-sectional improvements with routine 3R work to formulate the cost of improvements to the roadway. The cost estimation procedures for specific design elements are summarized in this section. Appendix A presents those procedures in full detail, including the equations used in cost estimation. Chapter 7 shows how the 3R improvement implementation costs are incorporated in benefitâcost analyses. 6.1 Lane Width Increasing the lane width of the traveled way can be included in a 3R project to reduce crash frequency and severity. The procedure to estimate the cost of increasing the lane width includes (a) the cost of base under the pavement for the additional lane width and (b) the cost of the pavement for the additional lane width. The cost is dependent on whether flexible or rigid pavement is used. Also included is the cost of milling and resurfacing the existing lanes. 6.2 Shoulder Width Increasing the shoulder width may be included in a 3R project to reduce crash frequency and severity. The method for constructing additional shoulder width depends on whether the lanes are being widened as part of the 3R project. If the lane width remains the same and the shoulder is paved, then the cost of increasing the shoulder width includes (a) the cost of base under the pavement for the additional paved shoulder width, (b) the cost of pavement for the additional paved shoulder width, and (c) the cost of milling and resurfacing the existing paved shoulder width. If the lane width remains the same and the shoulder is unpaved, then the cost of increasing the shoulder width simply is the cost of material for the additional unpaved shoulder width. If the lane width is increased, then the entire paved or unpaved shoulder width will be reconstructed regardless of whether the shoulder width is increased. In this scenario the procedure for calculating the cost of the paved shoulder includes (a) the cost of the base under the entire paved
61 shoulder width, and (b) the cost of the pavement for the paved shoulder width. The cost is dependent on whether flexible or rigid pavement is used. The cost of the unpaved shoulder in this scenario includes the cost of the material for the entire unpaved shoulder width. It is important to understand that even if the shoulder width remains the same, the cost of increasing the lane width includes the cost of having to reconstruct the shoulder. 6.3 Paving an Existing Unpaved Shoulder Paving an existing unpaved shoulder may be included in a 3R project to reduce crash frequency and severity. The cost of paving the shoulders includes (a) the cost of base under the pavement, and (b) the cost of pavement for the shoulder. 6.4 Roadside Slope Flattening the roadside slope may also be included in a 3R project to reduce crash frequency and severity. Both foreslopes (fill slopes) and backslopes (cut slopes) may be flattened, but the cost estimation procedures are based on flattening roadside foreslopes. The cost of flattening the roadside foreslope includes the cost of fill material required to build up the slope. The quantity of fill material required depends on the embankment height of the roadway. The embankment height in turn is dependent on the terrain of the roadway (see Appendix A). 6.5 Superelevation Improvement/Restoration on Horizontal Curves Restoring the superelevation on horizontal curves to Green Book guidelines may be included in a 3R project to reduce crash frequency. The cost of restoring the superelevation includes the cost of additional pavement required to attain the desired superelevation rate. 6.6 Rumble Strips Adding centerline and/or shoulder rumble strips may be included in a 3R project to reduce crash frequency. The cost of installing centerline and shoulder rumble strips simply depends on the length of rumble strip being installed. 6.7 Passing Lanes Adding passing lanes to rural two-lane highways should be included in a 3R project to reduce crash frequency only if a traffic operational study documents the need for passing lanes to attain the target LOS. The cost of adding a passing lane includes (a) the cost of base under the pavement for the passing lane, and (b) the cost of pavement for the passing lane.
62 6.8 Median and Roadside Barriers on Freeways Adding median and roadside barriers on rural and urban freeways may be included in a 3R project to reduce crash severity. The cost of adding additional median and outside barriers includes (a) the type of barrier being installed, and (b) the length of barrier being installed. If lane and/or shoulder width is being increased, existing barriers may need to be removed and re- installed. The cost of replacing the barriers in this scenario is included if necessary. 6.9 Right-of-Way The cost estimation procedure includes the cost of acquiring additional right-of-way. The edge of right-of-way is considered to be at the toe of the roadside foreslope. Any width added to the cross section is assumed to require acquisition of additional right-of-way. The unit cost of right- of-way is dependent on whether the road is in a rural or urban area (see Appendix A). 6.10 Incidental Costs The cost estimation procedure takes into account incidental costs that are likely to be part of the 3R project. The incidental costs depend on the road and area type. Appendix A presents these incidental costs in full detail.