HomeMy WebLinkAbout21 - Design Report - Northwest Crossing Ph 1 - Oak Streetmemo
Page 1
N:\5659\006_NWX_Phase1Design\04 Design\Reports\Road Design\5659.001_Oak-DesignMemo.docx
TO: City of Bozeman Engineering Department
FROM: Morrison-Maierle Inc
DATE: April 15, 2021
JOB NO.: 5659.006
RE: Northwest Crossing Phase 1 – West Oak Street Design Parameters
CC: MMI File
Urgent For Review Please Comment Please Reply For Your Use
Purpose:
The following document is intended to describe the design parameters for the proposed geometry
of West Oak Street along the southern boundary of the Northwest Crossing Subdivision. All
geometry was designed to meet AASHTO requirements as published in its “Policy on Geometric
Design of Highways and Streets” using a design speed of 50 mph.
Vertical Curves:
All proposed vertical curves meet the minimum K values stated below:
Crest Curves: K = 84 (min, Table 3-34)
Sag Curves: K = 96 (min, Table 3-36)
Note, the centerline profile was developed to match the spill curb on the north side of the existing
lanes of Oak Street.
Left Turn Lanes:
Left turn lanes on Oak Street are designed at the intersections of Rosa Way and Twin Lakes
Avenue for both direction of travel. The turn lanes are 12 feet wide with a taper length of 180 feet
(15:1). Storage lengths vary from 20 feet to 100 ft.
Median Openings:
Based on AASHTO Table 9-27, the minimum median opening width crossing through a 28-foot
wide median is 65 feet when median ends are bullet-nosed. The Rosa Way intersection median
opening is 68 feet wide and the Twin Lakes intersection median opening is 70 feet wide. Each
opening can accommodate the turning movements of a WB-40 design vehicle.