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a <br /> The cost calculations for typical street intersections were based on the lineal foot unit <br /> costs for different street widths and typical right-of-way widths for local and <br /> collector/arterial streets. Based on the average number of intersections per mile, the <br /> intersection cost per lane mile of arterial/collector streets including administration and <br /> engineering costs can be estimated. <br /> Note that the average number of intersections does not include the downtown grid. It <br /> was judged unlikely that the dense grid system of streets in downtown Eugene would <br /> ~ ~ be repeated elsewhere and thus avoids the potential for overestimating th_ a number of <br /> intersections per mile. <br /> 1.3.3 Traffic Signal Costs <br /> The City of Eugene keeps track of the total number of intersections with and without <br /> traffic signals currently in place for all streets in the Urban Growth Boundary (UGB). <br /> Records are maintained to account for the portion of state highway system jurisdiction <br /> separately from the City's local jurisdiction. Signalized intersections on state highways <br /> which intersect with Eugene's arterial and collector streets each count as one-half of a <br /> signal for purposes of SDC calculation. The total equivalent signals equal the total <br /> signals under Eugene's jurisdiction plus one-half of the shared jurisdiction signals. <br /> Dividing the total equivalent signals by the total number of lane miles of arterial and <br /> collector streets (a figure derived from Eugene maintenance records after subtracting <br /> turn lanes from the inventory), yields the total percent of signalized intersections per <br /> lane mile. <br /> Once again, it was judged unlikely that the density of signalized intersections in the <br /> downtown area would be repeated in newly-developing parts of the City. Accordingly, <br /> the number of signalized intersections per mile was reduced to reflect this factor. <br /> Estimates for the average cost of signalization per intersection include administrative <br /> and engineering costs. This estimated average cost is multiplied by the percent of <br /> signalized intersections per lane mile to calculate a component cost per lane mile for <br /> traffic signals. This cost per lane mile for signalization is added to the cost per lane mile <br /> of arterial and collector streets. <br /> 1.3.4 Bridges and Other Structure Costs <br /> i ~ It is likely that additional bridges will be constructed as development occurs. It is <br /> assumed that bridges required for new development will be in proportion to existing <br /> development, based on the City of Eugene's inventory of its bridge system, including <br /> Ferry Street Bridge and overpass. <br /> Several of the bridges are on local streets and are, therefore, not appropriately included <br /> in the cost calculation for arterial and collector streets. It was also judged unlikely that <br /> the close spacing of bridges over the Mill Race and Amazon Channel in the vicinity of <br /> downtown Eugene would be repeated in newly-developing areas. Accordingly, half of <br /> the short-span bridges in the central Eugene area were eliminated from the cost <br /> calculation. <br /> In addition to the small structures, the Ferry Street Bridge and the Ferry Street <br /> Overpass were listed in the inventory. Construction costs were totaled, including <br /> administration and engineering costs, and the total cost was divided by the total lane <br /> ~ " miles for the City's arterial and collector system, yielding an average cost per lane mile <br /> for bridge structures. <br /> <br /> City of Eugene SDC Methodology Transportation, Page,,B-6 <br /> <br />