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23 TABLE 18 Calculation of user delay cost Column A Column B Column C Column D Column E Total Number of Average Vehicle Vehicles Affected Delay Cost Additional Delay Classification By Work Zone1 Rate, $/hr2 Time, hour/vehicle3 Total Cost Passenger Cars 15 $10 to $13 Col. B* Col. C* Col. D Single-Unit Trucks 6 $17 to $20 Col. B* Col. C* Col. D Combination Trucks 1 $21 to $24 Col. B* Col. C* Col. D TOTAL (sum column B) (sum column E) 1 Only the number of vehicles in each category affected by the placement of the work zone over its entire duration. 2 From 1998 FHWA LCC report, p. 23 (note: 1996 values) (23). 3 The delay time for each vehicle is estimated on a project by project basis (it is the same for each vehicle category). This includes all delay times associated with the work zone, including speed change delay (going from posted speed limit to work zone speed limit), work zone speed delay (delay associated with slowing down to the work zone speed limit to traverse the work zone), stopping delay (time delay if a queue forms), and queue speed delay (time delay it takes to traverse the queue). produces a queue that generates considerable delay costs. a 0 to 100 scale by comparing all B/C ratios with the maxi- These costs may not be accurately accounted for in the user's mum individual B/C ratio (i.e., the ratio associated with the estimate of the number of vehicles affected by the work zone. optimal timing scenario). The maximum individual B/C ratio However, because work zones associated with most preven- is assigned an EI of 100, and all other B/C ratios are repre- tive maintenance treatments are of relatively short duration sented as a fraction of the maximum EI. The EI is computed and short length, queues are less likely to form and the error for each timing scenario using equation 1. associated with this item is reduced. ( B C)i EI i = × 100 (Eq. 1) (B C) max Additional Routine Maintenance Costs Different pavement structures and surfacing approaches where: require different needs for routine maintenance. These needs EIi = EI associated with the ith timing scenario are addressed in the methodology as a recurring cost for which (dimensionless). the timing is not optimized. An example of such an activity (B/C)i = B/C ratio associated with the ith timing is pothole patching that may influence long-term perfor- scenario. mance but does not fit the preventive maintenance model (B/C)max = Maximum of all of the B/C ratios associated because it is only done once the distress appears (i.e., its tim- with the different timing scenarios. ing cannot be optimized). i = Index associated with the current timing When choosing to include the costs of routine/reactive scenario. maintenance activities in an analysis, the do-nothing perfor- mance curves must account for the expected effect of this maintenance on performance. The routine maintenance sched- DETAILED CALCULATION PROCEDURES OF THE ANALYSIS APPROACH ule (and costs) must be estimated and included in the analysis. This section describes a step-by-step procedure for (1) com- puting benefit and costs within the methodology and (2) using Determination of Optimal Timing the results to determine the most effective treatment timing. An example is also presented to illustrate the concepts. The optimal time to apply a treatment is based on an analy- sis of benefit and costs. That application timing that maximizes benefit while minimizing costs (i.e., that with the largest B/C Step 1: Analysis Session Setup ratio is the most effective timing scenario. To make the actual values of the B/C ratios more meaning- The first step in the optimal timing analysis process is to ful, the concept of an Effectiveness Index (EI) is introduced. select the particular treatment and the specific treatment appli- The EI normalizes all individually computed B/C ratios to cation ages that will be used in the analysis.