3-01 ROAD CIRCULATION
Road circulation is important in road system design for the following reasons:
Operation of the arterial road system is improved by dispersing local traffic onto multiple roads and access points;
•Response time for emergency services is reduced;
•Time and mileage traveled by individuals and service providers, including school bus transportation, mail delivery, utilities, etc. is reduced; and
•Use of transit systems, and pedestrian and bicycle facilities, is promoted.
B. Layout and Design
The following criteria for road circulation shall be used in the layout and design of new road systems:
1) Road systems internal to developments shall be designed to promote the convenient circulation of traffic without reliance on the arterial road system. Circulation shall be provided in a manner, where possible, that will allow subsequent developments to meet these standards.
2) Road systems shall be designed with intersecting roads so that the maximum distance between intersections (measured from centerline to centerline), or between an intersection and a road end, does not exceed 800 feet in urban areas or 1320 feet in rural areas.
3) Road stubs shall be constructed to the boundary of adjacent parcels to create an interconnected road system, unless topography, critical areas or other factors make road construction impractical. A road stub proposal shall include information to demonstrate that the off-site road connection is constructible. That is, the location is such that an off-site road connection could be made that would avoid sensitive areas or topographical constraints, and be a feasible road location for adjacent land development.
4) A road serving more than 25 lots or 250 ADT shall be connected in at least two locations with another road or roads that meet the applicable standard(s) for the resulting traffic volume.
5) Block lengths in urban areas shall be between 125 feet and 800 feet. The roads defining a block shall comply with the minimum centerline offset
standards of Section 3-09. Access points within a block shall comply with the separation and corner clearance requirements of Sections 2-04 and 2-05.
6) A road connection shall be made to any road stub on an adjacent parcel that has been constructed to the shared boundary. This requirement may be waived by deviation where it can be shown that topography, critical areas or other factors make the connection impractical. However, a road connection shall be provided elsewhere to achieve the 800-foot (urban)/1320-foot (rural) road length criteria in Section 3-01.B.2 above.
7) Where a road stub on an adjacent parcel has been established by right-of-way or easement, but is not yet constructed to the shared boundary, then the road connection shall be constructed to meet the existing road on the adjacent parcel. This requirement may be waived by deviation where it can be shown that topography, critical areas or other factors make the connection impractical. However, a road connection shall be provided elsewhere to achieve the 800- foot (urban)/1320-foot (rural) criteria above.
8) The Engineer may determine that a non-motorized connection (shared use path or bikeway) between developments is appropriate in place of a roadway, through the deviation process.
From Snohomish County Engineering Design and Development Standards, 3rd Edition, p 31
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