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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 be <br />repeated elsewhere and thus avoids the potential for overestimating the 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 />tum lanes from the inventory), yields the total percent of signalized intersections per lane <br />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 and <br />engineering costs. This estimated average cost is multiplied by the percent of signalized <br />intersections per lane mile to calculate a component cost, per lane mile for traffic signals. <br />This cost per lane mile for signalization is added to the. cost per lane mile of arterial and <br />collector streets. <br />1.3.4 Bridges and Other Structure Costs <br />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 Miil Race and Amazon Channel in the vicinity of <br />downtown Eugene would be repeated in newly-developing areas. Accordingly, half of the <br />short-span bridges in the central Eugene area were eliminated from the cost calculation. <br />In addition to the small structures, the Feny Street Bridge and the Ferry Street Overpass <br />were listed. in the inventory. Construction costs were totaled, including administration <br />and engineering costs, and the total. cost was divided by the total lane miles for the City's <br />arterial and collector system, yielding an average cost per lane mile for bridge structures. <br />May 1, 1997 City of Eugene SDC Methodology Page C-6 <br />