Geometric Approval of Preferred Project Alternative (Horizontal. This task includes the preparation of preliminary engineering drawings and roundabout design check calculations to obtain geometric approval of the preferred project alternative developed under Task 2.3.3. If the preferred project alternative is a roundabout, preliminary engineering drawings will be prepared to identify the horizontal design limits of critical roundabout geometric elements such as curb geometry, lane widths, channelization, lane transitions, splitter islands, pavement markings, fastest path, sightlines, and conform conditions to either the existing street infrastructure or proposed typical street section. The functional area of the roundabout intersection will be defined. Typical sections of each leg, including the roundabout circulatory roadway and central island will be prepared. Design checks specific to vehicles navigating roundabout intersections will be calculated and documented in a Roundabout Performance Check Summary Memorandum. Roundabout curb geometry and lane markings will be adjusted to achieve target design values for estimated speeds, design vehicles, and sight lines. If site conditions or other constraints require a deviation from guidance described in NCHRP Report 672, the deviation will be identified in the Roundabout Performance Check Summary Memorandum along with a description why the deviation is being requested. The following design checks will be evaluated for vehicles: • Fastest path estimation for R1 through R5 • Swept path and tire tracking for design vehicles (Assume up to two design vehicles) • Intersection angle of visibility • Intersection Sight Distance (Assume tc=5.0 seconds) • Stopping Sight Distance • Path overlap estimation for multi-lane entries and departures Optional Task: An assessment of pedestrians crossing at the roundabouts is not included in this scope. Pending new Public Right of Way Accessibility Guidelines (PROWAG) from the United States Access Board, an assessment conducting crossing performance checks for pedestrians with vision disabilities consistent with NCHRP Report 834: Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities may be beneficial, but is not required now. As an optional task, KHA can develop an additional scope and fee to conduct a pedestrian crossing assessment that includes the following three performance checks: Crossing sight distance (for pedestrians) Estimated level of pedestrian crossing delay Expected level of risk...
