HomeMy WebLinkAboutHARMONY COTTAGES (AFFORDABLE HOUSING) - PDP - PDP150030 - SUBMITTAL DOCUMENTS - ROUND 1 - VARIANCE REQUEST1218 W. ASH, STE. A, WINDSOR, COLORADO 80550
TEL. 970.674.3300 – FAX 970.674.3303
December 16, 2015
Mr. Marc Virata
City of Fort Collins – Engineering
PO Box 580
281 North College Avenue
Fort Collins, Colorado 80522-0580
RE: Harmony Cottages - Street Sight Distance Variance
Interwest Project 1255-028-00
Dear Marc:
Habitat for Humanity is proposing a housing development along the south side of Harmony Road
(classified as a 4 Lane Arterial) near the southeast corner of the intersection with Taft Hill Road.
This project is required to establish sight distance triangles and easements per the 4 Lane Arterial
standards and design speeds. A variance is requested from Table 7-3 “Fort Collins (GMA
and City Limits) Street Standards – Technical Design Criteria” and Figure 7-16 “Sight
Distance (Sight Triangle)” in the Larimer County Urban Area Street Standards to allow
the project to apply the sight distances in reference to AASHTO’s current A Policy on
Geometric Design of Highways and Streets.
The proposed Harmony Cottages development has frontage on both Taft Hill Road and Harmony
Road. However, due to the close proximity to the Taft Hill / Harmony intersection, city staff has
requested that the development not provide an ingress/egress drive off of Taft Hill Road.
Therefore, a single point of access along Harmony Road has been selected that attempted to
balance proximity to the intersection and maximizing available sight distance along Harmony
Road.
Harmony Road was realigned in 1998 to its current “S-Curve” configuration and is posted at 40
mph. Based on the close proximity of the proposed driveway to the Taft Hill and Harmony Road
intersection and industry standard guidelines related to design speed being approximately 5 mph
over the posted speed, a design speed of 45 mph is desirable in this situation.
We reviewed the sight distance calculations in reference to current (2011) AASHTO edition of A
Policy on Geometric Design of Highways and Streets. As Harmony Road is a 4 Lane roadway,
the calculations provided within the AASHTO guidelines account for additional delays
anticipated for a vehicle crossing additional lanes of traffic when exiting the site. Below are
calculations for the intersection sight distance based on two different scenarios:
Harmony Cottages December 16, 2015
Harmony Road Sight Distance Variance Page 2 of 2
Passenger Vehicle Intersection Sight Distance (ISD)
ISD = 1.47 x Design Speed x Time Gap
ISD = 1.47 x 45 mph x (7.5 + 0.5)
ISD = 529 feet
The available sight distance from the proposed intersection with Harmony Road has been
calculated to be 675 feet; therefore, the available sight distance for a passenger vehicle exceeds
the required sight distance of 529 feet and is deemed adequate for this application.
In addition to the standard passenger vehicle calculation we analyzed the minimum sight
distance based on a single unit truck exiting the site, although for a residential development such
as Harmony Cottages this would be an atypical application.
Single Unit Truck Intersection Sight Distance (ISD)
ISD = 1.47 x Design Speed x Time Gap
ISD = 1.47 x 45 mph x (9.5 + 0.7)
ISD = 675 feet
The minimum sight distance for a single unit truck is also within the available intersection sight
distance of 675 feet and is deemed adequate for this application. The Preliminary Subdivision
Plat submitted with the PDP Application reflects a proposed Sight Distance Easement along the
property frontage that corresponds with this more conservative 675 foot line of sight.
Attached is an exhibit showing both AASHTO sight distance triangles for the proposed access to
Harmony Road.
Based on the provided calculations for required and available sight distance at this intersection,
we do not anticipate that this variance will be detrimental to the public health, safety, or welfare.
Please call me at (970) 460-8487 should you have any questions or require any additional
information for the approval of this variance.
Sincerely,
Robert Almirall, PE
Sr. Project Manager