Heartz Road/PP-CS 881206COPPELL PUBLIC WORKS
December 6, 1988
Taryon Bowman, P & Z Coordinator
Stev~n M. Morton, Chief Public Works Inspector
Heartz Rd. Preliminary
,) On north end right-of-way makes a curve to left. What will be required of ease-
ments east of proposed right-of-way at Parkway Blvd. for 8" sanitary sewer.
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COPPF. LL PUBLIC WORKS
December 5, 1988
TO:
FROM:
RE:
Taryon Bowman, Planning & Zonin~Coordinator
Howard Pafford, Water Foreman
Heartz Road Preliminary Plat
I have not yet reviewed the revised set of plans. Therefore my comments
will be made at or after the DRC pre-agenda meeting.
HLP/sm
THE CITY WITH A
BEAUTIFUL FUTURE
HANDWRITTEN
MEMORANDUM
SUBJECT:
DATE~-Y° ~
MESSAGE: ~/f%/C.~ 2~ C;(]~'~ NTT~vO THE
HANDWRITTEN
MEMORANDUM
Box
8~0 Transportation and Traffic Engineering Handbook
The 85-percentile speed as determined by spot speed studies is the principal factor
generally used by traffic engineers to determine speed limits. Although this method is
highly satisfactory on streets and highways carrying moderate to heavy volumes of
traffic, it is difficult to apply on low-volume roads because of the time consumed in
gathering the necessary number of observations. In such cases, trial runs can serve as
a satisfactory substitute.
Criteria for establishing speed limits. The Traffic Committee for the American
Association of State Highway Officials adopted in 1970 the following policy statement
for the establishment of speed zones:
The 85th percentile speed is to be given primary consideration in speed zones below
50 miles per hour, and the 90th percentile speed is to be given primary consideration
in establishing speed zones of 50 miles per hour or above. To achieve the optimum
in safety, it is desirable to secure a speed distribution with a skewness index approach-
ing unity.
Signing for speed Emits. Signing for speed limits should be consistent with the
appropriate sections of the latest edition of a manual on uniform traffic control
devices, or an equivalent, used in each country (see Chapter 16, Traffic Signs and
Markings).
Signs for speed limits are erected at vary ng intervals, depending on highway type
and general location. In urban areas, speed limit signs are usually erected at intervals
not exceeding one-half mile if the speed limit is 40 mph or less. On freeways and in
rural areas, frequency of signing varies considerably, with intervals between signs
usually ranging from one to five miles.
DETERMINATION OF ADVISORY SPEED INDICATIONS
Two basically different methods are available for determining advisory speed
limits on horizontal curves: (1) by trial speed runs with a test vehicle or (2) by office
calculation. Either method is satisfactory, but field runs to check the office calculations
are desirable in any event.
The trial speed runs method involves using a vehicle equipped with a bald-bank
indicator to show the combined effect of the body roll angle, the centrifugal force angle,
and the superelevation angle. Safe speeds on curves are indicated by ball-bank readings
of 14° for speeds below 20 mph, of 12° for speeds between 20 and 35 mph, and of I0°
for speeds of 35 mph and higher. Also, 10° is safe for 50 mph and even 60 mph, but
for higher speeds a smaller reading should be used J:
In using the office method for determination of advisory speed, the advisory
speed indication for a curve may be calculated by the following formula:
V = ./~ + f)R = ~/15~-~f)R '¥ 0.067
where V = advisory speed of vehicle in mph,
e = superelevation in ft per ft of horizontal width,
f = transverse coefficient of friction,
R = radius of curvature in ft.
n A Policy on Geometric Design of Rural Highways (Washingon, D.C.: American Association of State
Highway Officials, 1965), p. 154.
Speed Regulations and Other Operational Controls 861
Thc formula is solved for thc advisory speed on the curve. Thc resulting speed should
be rounded to the nearest 5 mph for signing in the field.
5730 .
If D is used as the degree of circular curve, arc definition, D ~ -~- ann the stan-
dard formula becomes:
Using this formula, and with given values for e and f, the minimum radius and the
maximum degrees of curvature for the designated design speeds have been computed
as shown in Table 18.2.
TABLE 18.2
Maximum Degree of Curve and Minimum Radius Determined
for Limiting Valaes of e andf
Max. Degree
Design Maximum Maximum Total Minimum Max. Degree of Curve,
Speed e f (e + f) Radius of Curve Rounded
30 .06 .16 .22 273 21.0 21.0
40 .06 .15 .21 508 t 1.3 I i.5
50 .06 .14 .20 833 6.9 7.0
60 .06 .13 .19 1263 4.5 4.5
65 .06 .13 .19 1483 3.9 4.0
70 .06 .12 .18 1815 3.2 3.0
75 .06 .11 .17 2206 2.6 2.5
80 .06 .11 .17 2510 2.3 2.5
30 .08 .16 .24 250 22.9 23.0
40 .08 .15 .23 464 12.4 12.5
50 .08 .14 .22 758 7.6 7.5
60 .08 .13 .21 1143 5.0 5.0
65 .08 .13 .21 1341 4.3 4.5
70 .08 .12 .20 1633 3.5 3.5
75 .08 .11 .19 1974 2.9 3.0
80 .08 .11 .19 2246 2.5 2.5
30 .10 .16 .26 231 24.8 25.0
40 .10 .15 .25 427 13.4 13.5
50 .10 .14 .24 694 8.3 8.5
60 .10 .13 .23 1043 5.5 5.5
65 .10 .13 .23 1225 4.7 4.5
70 .10 .12 .22 1485 3.9 4.0
75 .10 .11 .21 1786 3.2 3.0
80 .10 .11 .21 2032 2.8 3.0
30 .12 .16 .28 214 26.7 26.5
40 .12 .15 .27 395 14.5 14.5
50 .12 .14 .26 641 8.9 9.0
60 .12 .13 .25 960 6.0 6.0
65 .12 .13 .25 1127 5.1 5.0
70 .12 .12 .24 1361 4.2 4.0
75 .12 .11 .23 1630 3.5 3.5
80 .12 .11 .23 1855 3.1 3.0
Source: A Policy on Geometric Design of Rural Highways (Washington, D.C.: American Association of
State Highway Officials, 1965), p. 138.
IS-18 Hiltmly Eqill~illl
Where practical, the side slopes should be 4 (horizontal) on 1 (vertical), or flatter. Side slopo~/
should not be steeper than 2:1. except when special stabilization treatinents are used or where
rock excavation or embankment is encountered.
Right of Waft. The highway right of way should be as wide as feasible, consistent with location
and cost. In every case. the right of way should, however, be not less than that required for all
elements of tbe design cross section and the appropriate border areas. Such berder areas may
vary from a few feet in highly developed areas to 100 ff or more in rural areas, where lower land
values prevail.
GeometrieDesign St~n&rds--S~eon&r,ff Ro~tus. Table 16-10 illustrates geometric design
standards for secondary highways of different classifications, as adopted by the New York State
Department o£ Transportation. [The same qualification regarding eompetibi]ity with Ameriean
Association of State Highway and Transportation Oltleials (AASHTO) standards as given previ-
ously for primary and interstate mutes applies here.]
16-10.
~.From "Highway Design Ma~uar' (Vol. 1), Facilities Design Suhdlvision, New York State Department of
Transportation
Geamaiflc ~ Stlnd~ls 1&IS
The following standards are ha.sed to a large extent on data given in "Geometric- Design Stan-
dards for Highways Other than Freeways." "Geometric Design Guide for Local Roads &
Streets,' "A Policy on Geometric Design of Bural Highways,' and "A Policy on Arterial High-
ways for Urban Areas," American Association of State Highway and Transportation Officials,
Washington, D.C.
Number and Width of Lanes. The number of lanes in each direction is determined on the
basis of the design traflle volume and the desired level of service. Where warranted, special
lanes for turning vehicles should be provided. Parking areas (generally 8 to 10 fi wide) are neces-
sary on certain urban highways and major streets.
Normal lane width of 12 ft is desirable (with a 1- or 2-ft additional off, set on curbed sections). In
some instances, however, such as in heavily developed areas where right of way is limited, lane
width can be reduced to 11 ft and even, although this is undesirable, to 10 ft.
Shoulders. Minimum usable width of shoulder should be at least that given in Table 16-10.
Medians. Where there are more than two lanes, medians are desirable. The same considera-
tions that were outlined previously for primary routes would generally apply, with variations to
suit individual site conditions.
Sight Distance. For determining stopping sight distance (a vertical-curve factor for divided
roadways), assume the height of eye is 3.75 fl and height of object 0.5 fi above grade. For deter-
mining passing sight distance (a vertical-curve factor for undivided roadways), assume the height
of eye is 3.75 ft and height ofobject is 4.5 fi above grade. Table 16-11 gives values of a coefllcient
K by which the difference in grades at a change in highway slope may be multiplied to obtain the
length, fl of vertical curve that will provide the minimum sight distance (see also AfL 16-7).
For a more in-depth discussion of stopping sight distance criteria, see AASHTO, "A Policy on
Design Standards for Stopping Sight Distance."
*From "A Policy on Design Standards for Stopping Sight Distance." American Ass~iation of St~/e Highway
and Transportation O~eials.
tK value is a coe~eient by which the algebraic difference in grade may be multiplied to determine the
length, fl, of vertical curve that will provide minimum sight distance.
Curvature and Superelevation. Maximum horizontal curvatures for various design speeds
and rates of roadway superefevation are presented in Table 16.12.
Superelevations for rural highways generally should not exceed 0.10 or 0. t2 ft per fL If snow
or ice conditions prevail, superelevations should not exceed 0.0B or 0.08 fl per ft. For urban
highways, superelevation should not exceed 0.06 or 0.08 ft Per fi (0.06 ft Per ~ is usually used as
a design maximum). Table 16-13 gives minimum lengths for superelevation runout in two-lane
pavements.
Maximum Grades. Maximum grades for various design speeds and lypes of terrain are listed
in Table 16-14.
Clearances. Vertical clearance at underpasses should be at fe~t 14 ft over the entire road-
way width, including the shoulders. An allowance of 6 in. should be added for resurfaeing.
Horizontal clearances, both right and left on structures, from edge of traffic lane to face of para-
pot or railing, should be equal to the width of the entire roadway section, including the usable
shoulders. In special eases, such as on extremely long structures or in tunnels, reduced clear-
{CEPT
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