Attachment 8- Road Design Standards e
• CITY OF ClIANHASSEN
9 S Chanhassen isa Community for Life-Providing for Today and Planning for Tomorrow
NH AS
MEMORANDUM
TO: Todd Gerhardt, City Manager
FROM: Stephanie Smith, Project Engineer
DATE: September 25, 2017
SUBJ: Road Design Standards
Issue
The City Code requirements for vertical curves of public street design in subdivisions are not
consistent with MnDOT's Roadway Design Manual(RDM). The current code requirement is more
restrictive than the RDM. The RDM requires a more precise calculation of the sight distance for the
vertical curve,therefore is more accurate. This difference has created confusion for development
engineers and has reduced design flexibility.
Alternatives
1. Do nothing. Our code requirement will continue to require street standards that differ from
MnDOT's recommendations.
2. Amend Section 18-57 (h) to require public streets to follow the most recent version of
MnDOT's Roadway Design Manual.
Recommendation
Staff recommends Option 2 to make vertical curve design constant with state agencies. The
revised ordinance could read:
Sec. 18-57. - Streets.
(h) Different connecting street grades shall be connected with vertical curves. Minimum
length, in feet, of the vertical curves shall be 20 times the algebraic difference in the
percentage of grade of the two adjacent slopes. The vertical curve length shall conform to
the most recent state standards for the proposed speed.
G:\PLAN\City Code\2017\Various\Road Design Standards Code Amendment Paper
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