Capital Hill PUD Traffic Safety Analysis <br />(Revised) May 17, 2017 <br />development within or close to the right-of way and/or right-of way setbacks identified in <br />applicable City of Eugene Development Code. Conflicting private development includes: retaining <br />walls, fences, buildings, parking areas and driveways. <br />2.1.3 Sight Distance <br />The existing driveway intersections on Capital Drive are located between Cresta De Ruta Street <br />and the end near Hendricks Park. All of the existing four site driveways are planned to be <br />retained to continue to serve current residences on the site in their existing function and <br />capacity, while two of them will be reutilized as a looped connection through the site to provide <br />access and circulation for the proposed new development and parcel frontages. <br />Driveway intersection sight distance was measured in the field at the two existing site driveways <br />that will provide access to new development on the site and at the proposed new access within <br />the apex area of the curve that will serve proposed lots 19 and 20. Recommended intersection <br />sight distances based on the American Association of State Highway and Transportation <br />Officials' (AASHTO's) A Policy on Geometric Design of Highways and Streets, (61h Edition-2011) are <br />calculated from the following equation: <br />ISD = 1.47 V _j_tg <br />Where: <br />ISD= Intersection Sight Distance = the length of visible roadway (long leg of the sight <br />triangle) along the major road (ft) as measured from the departing driver's <br />observation point 14.5 feet back from the near edge of the traveled way at an <br />assumed driver's eye height and object height of 3.50 feet above the road surface <br />Vma,or =design speed of major road in mph <br />to =time gap (seconds) for departing driveway vehicle to enter the major road <br />The time gap is assumed to be 7.5 seconds for a stopped passenger vehicle to turn left onto a <br />two-lane highway with no median and 6.5 seconds for a stopped passenger vehicle to turn right <br />into the nearest travel lane or cross the intersecting street. The time gap is considered the <br />shortest acceptable gap in the traffic stream that a driver in the departing vehicle is willing to <br />accept when maneuvering from the driveway (minor approach) onto the roadway (major <br />approach) and accelerate to the design traffic speed. The assumed time gap is adjusted for <br />minor street approach upgrades exceeding three percent by adding or subtracting 0.2 seconds <br />for each percent grade. The time gap may also be adjusted for the number of lanes crossed when <br />a roadway has multiple travel lanes per direction by adding 0.5 seconds for each additional lane <br />crossed (one lane per direction is assumed in the default time gap value). <br />The existing site driveway intersections do not require adjustments to increase the time gap <br />since they are not located on uphill approaching minor street grades and since departing <br />maneuvers do not cross more than one lane of travel. Based on the statutory speed of 25 MPH <br />and rounding up to the nearest five-foot increment, the calculated AASHTO recommended <br />intersection sight distance would be 240 feet when looking to the left and 280 feet when looking <br />to the right (ISD based on left turns for sight distance to the right and right turn/crossing <br />maneuvers when looking to the left). AASHTO recommendations are based on typical gap <br />acceptance where a departing vehicle is entering a stream of traffic, and it is implied that there <br />are a significant number of other road users on the major road approach. The street character, <br />function, and associated relatively low traffic volumes on Capital Drive justify a reduced <br />acceptable intersection sight distance as will be demonstrated later. <br />© Branch Engineering, Inc. <br />Page 1 5 <br />