HomeMy WebLinkAboutBURNS RANCH AT QUAIL RIDGE RF REVIEW FINAL - 23 90C - SUBMITTAL DOCUMENTS - ROUND 1 - TRAFFIC STUDYu.i
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MEMORANDUM
To: Rex Burns
Eldon Ward, Cityscape
Kevin Gingery, RBD
Mike Herzig, Fort Collins Development Engineer
Kirsten Whetson, Fort Collins Planning Department
Rick Ensdorff, Transportation Department
From: Matt Delich "`Z2
Date: June 7, 1991
Subject: Burns Ranch stacking and stopping distance analysis
(File: 9127MEM1)
This memorandum documents the traffic operation aspects
of the Burns Ranch access via Skimmerhorn Street, west of
Overland Trail. This memorandum addresses two specific
concerns expressed by Mike Herzig in response to the variance
request regarding the grade of Skimmerhorn Street.
At full build -out of the Burns Ranch, there will be 36
dwelling units. The time of peak exits will occur in the
morning when residents are typically going to work. Using the
ITE Trip Generation Manual, these 36 dwelling units will
produce 20 vehicular exits from Skimmerhorn Street during the
peak hour. Using an extremely conservative analysis approach,
I assumed that all 20 exits will occur during the peak 15
minutes of the peak hour. This would produce 1.33 vehicle
exits per minute. I have assumed a future ADT of 10,000 on
Overland Trail. This is higher than any estimates that I am
aware of for this segment of Overland Trail. Using typical
morning peak hour ratios, there would be a volume of 800 on
Overland Trail in the peak hour. Again, taking a conservative
approach, I assumed that all 20 exits would turn left at
Overland Trail. Using recent research, regarding delays to
left -turning vehicles at stop sign controlled intersections,
indicates that the delay would be 5-15 seconds per approach
vehicle. It is concluded that no more than one vehicle would
be present when a second vehicle approached from the west.
Therefore, the maximum storage necessary is for one vehicle.
City staff expressed concern over the grade of
Skimmerhorn Street and the ability of a vehicle to stop at the
bottom of the grade. Three street grade combination
alternatives were analyzed:
1. RBD design solution - From the flowline
be 40 feet at 2% and then have a
Skimmerhorn Street to access the Burns
P.I., there would
grade of 10% on
Ranch.
0
2. Rex Burns suggested design solution - Carry the
superelevation (3.6%) of Overland Trail through the
flowline for 125 feet and then have a grade of 13.5% on
Skimmerhorn Street to access the Burns Ranch.
3. Fort Collins design solution - From the flowline P.I.,
there would be 125 feet at 2% and then have a grade of
14% on Skimmerhorn Street to access the Burns Ranch.
The design conditions assumed a speed of 30 mph and wet
pavement (f. = 0.35). It was further assumed that one vehicle
would be waiting to exit Skimmerhorn Street. Therefore, 25
feet was subtracted from the flatter grade adjacent to
Overland Trail. Perception and reaction time does not need
to be considered, since the approaching vehicles will have
ample time and distance to perceive and react. Only the
actual braking distance was considered. The equation used to
calculate the braking distance was:
d = VZ/30 (f + G)
where: d = braking (stopping) distance in feet
V = speed (30 mph)
f = coefficient of friction for wet pavement
(0.35)
G = grade of street
The results of the analyses are as follows for each
alternative:
1. The braking distance is 115 feet with 15 feet occurring
on the 2% segment and 100 feet occurring on the 10%
segment.
2. The braking distance is 96 feet with all of it occurring
on the 3.6% segment.
3. The braking distance is 91 feet with all of it occurring
on the 2% segment.
It is concluded that there is little difference in the
braking distance between any of the alternatives. From an
operations and safety perspective, there are no clear- choices.
It is my tncommendntion that if there is an alternative that
aids in accomplishing other engineering design solutions, that
is the one to choose.