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Pages 59-71

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From page 59...
... 59 This section describes the development of a truck LOS model framework that is sensitive to the facility performance measures that are most important from the perspective of shippers, receivers and carriers, tempered with the need to provide actionable information to public agencies for the improvement of truck movements on the facility. The truck LOS model development process started with the Cambridge Systematics New York/ New Jersey Cross Harbor Freight Movement Model (Cambridge Systematics, in process)
From page 60...
... 60 incorporating truck Analysis into the Highway capacity Manual Since designation of the National Freight Network is not expected until after preparation of this report, a tentative three-class system (shown in Exhibit 28) employing some of the general criteria outlined in MAP-21 is recommended for classifying highway facilities by their relative importance to the region's and national economy.
From page 61...
... truck Level-of-Service Framework 61 6.2.1 Translation of Utility to LOS The utility index output by the Cambridge model must be translated into an equivalent letter grade LOS. This is done by comparing the computed utility for actual conditions on the facility with the estimated utilities for the theoretically best- and worst-case conditions on the facility.
From page 62...
... 62 incorporating truck Analysis into the Highway capacity Manual The same approach is used to estimate the effect of worse-case conditions on average shipment times. The difference between the agency selected worst-case congested travel time and the free-flow travel time for the facility is added to the average shipment time obtained from FHWA's FAF.
From page 63...
... truck Level-of-Service Framework 63 Estimation of Effect of Tolls on Average Shipment Cost The Cambridge model requires average shipment cost by commodity type. Changes in facility tolls would change that cost upwards or downwards.
From page 64...
... 64 incorporating truck Analysis into the Highway capacity Manual Computation of Composite Utility The Cambridge model computes utility for individual commodity types. A composite utility is computed for trucks on the facility by weighting the utility for each specific commodity type by its proportion of total truck commodity flows (in tons)
From page 65...
... Truck Level-of-Service Framework 65 where OTA = on-time arrival contribution to utility equation (utils) and POTA = probability of on-time arrival expressed as a proportion (unitless)
From page 66...
... 66 incorporating truck Analysis into the Highway capacity Manual Thus, the median (50th-) and 95th-percentile TTIs are 50% 2 1 Equation 16 1 TTI kc( )
From page 67...
... truck Level-of-Service Framework 67 6.3.5 Prorating Reliability Effects by Facility Length During testing of the streamlined model, it was noted that it significantly overestimated the value of reliability, incorrectly suggesting that shippers would be willing to pay tolls of $10 to $30 per mile for 90% probabilities of on-time arrival. Upon re-evaluation of the Cambridge model, it was noted that the reliability effect applied to the entire shipment distance rather than just the facility length.
From page 68...
... 68 Incorporating Truck Analysis into the Highway Capacity Manual speeds, and no tolls) , the identification of worst-case conditions is less obvious.
From page 69...
... truck Level-of-Service Framework 69 best- and worst-case conditions; therefore, other methods must be explored to reduce the sensitivity of Model 3 to varying facility lengths. Revisiting the utility function in Model 2 (Equation 19)
From page 70...
... 70 incorporating truck Analysis into the Highway capacity Manual Toll/mi = Toll rate paid by trucks to use facility ($/mile) ; FFS = Free-flow speed for trucks on facility (mph)
From page 71...
... truck Level-of-Service Framework 71 This model is obtained by dropping tolls and the TTI portions of the utility equation from Model 3. The logistic function and parameters of Model 3 are retained.

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