Waterside P2-CS030827Teresa Turner - Re
From:
To:
Date:
Subject
Mr Gray,
Westlake & Greenway
Teresa Turner
Daniel D Gray
8/27/03 9:00:04 AM
Re: Westlake & Greenway
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The construction plans show the grade on Greenway as it approaches Westlake to be 1.7 %. Using a
4 -foot digital level, actual grades were measured at several locations just west of the intersection and they
ranged from 1.6% to 1.8 %. So the street was constructed according to the plans.
You had a question concerning vertical measurement and I am not exactly sure what you are asking. A
2 -foot tall object was placed in the center of the intersection. Using a 3.5 -foot high pole as a reference,
the distance was measured from where the 2 -foot tall object was lost from view. Essentially, the top
section of the object was visible to Greenway's intersection with Samuel. The object height and driver's
eye level used were in accordance with AASHTO's 2001 policy.
Please let me know if you have any other questions.
Teresa Turner
City of Coppell
Engineering Department
972- 304 -3681
>>> "Daniel D Gray" < daniel d graV(d)fanniemae.com 8/24103 12:31:03 PM >>>
Thanks for taking the time to look into this.
I am not clear on whether this was built according to plan. I understand you
are looking at the requirements since the 2001 AASHTO study. You had
mentioned that you wanted to see if it was built to plan. I am not sure
whether this means that it was built according to the plan requirements set
forth years ago or not. Also, can you confirm what the vertical measurement
was when you recently measured it and where the measurement was taken
from. If so, did it meet the plans that were submitted for the
development?
Also, I should mention that there was a car accident recently at this
intersection.. It may not be the 5th in the year, but it is noteworthy. Mr.
Rafiki (corner lot across street from Westlake) was hit by a car as he was
entering his driveway.
Thanks again for your efforts on this.
Dan
Ken Griffin wrote:
> Mr. Gray
• Sorry for the delay in responding to your request. I received the
• follow up report on August 7, 2003. The delay in the report was
• securing a 2001 copy of the " AASHTO Policy on Geometric Design of
• Highways and Streets ". That manual details how to calculate sight
• distance at an intersection. The criteria states that a drivers eye is
• measured at 3.5 feet above the pavement and the object to see is
• measured at 2 feet above the pavement. The 2 foot object height is
Teresa T urn er - Re: Westlake & Greenway
• different that the information that was in my reference book. The
• previous versions of the "Policy" stated that the object height was
• measured at 6 inches. Once the discrepancy was noted, we obtained the
• most recent version of the "Policy" and recalculated the sight
• distance.
• The criteria we used was: the 90% speed of 35 mph; driver height of 3.5
• feet; and object height of 2 feet.
• The stopping sight distance is comprised of the reaction time distance
• and the actual braking distance. Based on the slope of the road and a
• speed of 35 mph, the reaction time distance was 128 feet. This is the
• distance that a vehicle would travel during the time that the driver
• reacted, ie, distance traveled while the driver perceived that there was
• a need to stop. The actual braking distance was 123 feet. Therefore
• the total sight distance needed is 251 feet. The minimum stopping
• distance required for a street posted 30 mph is 200 feet based on City
• Ordinance and the "Policy ". The difference between the 251 and the 200
• takes into account the actual 90% speed on the street and the grade of
• the street.
• Using the 3.5 foot height of driver and the 2 foot height of an object
• from the 2001 "AASHTO Policy on Geometric Design of Highways and
• Streets ", there is a sight distance of about 950 feet. This is
• generally the distance from Samuel to Westlake.
• This intersection does not meet any requirement (traffic volume,
• accidents, pedestrian volume, or sight distance restrictions) that would
• warrant the installation of a four way stop sign.
• Again, I sorry for the delay. If you have any additional questions you
• can contact me via phone or email.
> Ken Griffin, P. E.
> Director of Engineering /Public Works
> 972 - 304 -3686
> kgriffin(a )ci.coppell.tx.us
• > "Daniel D Gray" < daniel d grav(o)fanniemae.com 08/18/03 08:24AM >>>
• Following the City Council meeting at which I made a presentation
• regarding my concerns about the intersection of Greenway and Westlake,
• the City Engineer told me he would have someone call me the following
• week concerning a measurement of the vertical incline on Greenway to
> see
• if it might qualify for a stop sign. Although the plans indicated that
• it would not, he noted that sometimes things aren't exactly built to
• plans and he wanted to have it measured. I also looked at the incline
• after our conversation and noticed that the vision is further
• restricted
• by the height of the sidewalk which stands even higher than the
• street.
• It has been over a month since the City Council meeting and I haven't
• heard anything on this issue. I am hoping that someone might be able
• to
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> update me on the measurement.
Teresa Turner - Re: Westlake & Greenway
> Thank you.
* Daniel Gray
* 214-402-3239
CC: Ken Griffin
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