City of Frisco Engineering Standards

Engineering Standards
TABLE 2.3: Minimum Acceptable Crest Curve Given Speed and Difference in Grade of Road
Design
Speed, V
(MPH)
SSD
(ft)
K
Length of Vertical Curve (L=KA)
A=1.6 A=2 A=3 A=4 A=5 A=6 A=7 A=8 A=9 A=10
25 155 12 50 50 50 50 60 80 90 100 110 120
30 200 19 50 50 60 80 100 120 140 160 180 190
35 250 29 50 60 90 120 150 180 210 240 270 290
40 305 44 70 90 140 180 220 270 310 360 400 440
45 360 61 100 130 190 250 310 370 430 490 550 610
50 425 84 140 170 260 340 420 510 590 680 760 840
TABLE 2.4: Minimum Acceptable Sag Curve Given Speed and Difference in Grade of Road
Design
Speed,
V
(MPH)
SSD
(ft)
K
Length of Vertical Curve (L=KA)
A=1.6 A=2 A=3 A=4 A=5 A=6 A=7 A=8 A=9 A=10
25 155 26 50 60 80 110 130 160 190 210 240 260
30 200 37 60 80 120 150 190 230 260 300 340 370
35 250 49 80 100 150 200 250 300 350 400 450 490
40 305 64 110 140 200 260 320 390 450 520 580 640
45 360 79 130 160 240 320 400 480 560 640 720 790
50 425 96 160 200 290 390 480 580 680 770 870 960
E. Standard Intersection Layout
1. Street intersections shall intersect at ninety degree (90º) angles. Intersection approaches for
Type A and B thoroughfares shall remain perpendicular for a minimum distance equal to the
corresponding design speed Stopping Sight Distance (SSD) identified in Table 2.1. For
residential collector and/or local street intersections, up to a five degree (5º) tolerance is
allowable.
2. When the classification of a thoroughfare changes as it crosses an intersecting street, the
design of both thoroughfare approaches shall maintain the characteristics of the higher class
thoroughfare for a minimum distance specified by the Director of Engineering Services.
3. The through lane(s) on one approach shall align with the receiving lane(s) on the other side of
the intersection. If pre-existing physical encroachments make an offset necessary, a through
lane can be offset no more than six feet (6’) from its receiving lane when crossing a Type B
or smaller thoroughfare and offset no more than eight feet (8’) when crossing a Type A
thoroughfare. These requirements apply to both public street and private driveway
approaches to an intersection.
4. The curb radii shall be a minimum of twenty feet (20’) where Type D, E, F, and G
thoroughfares intersect with Type D, E, F, and G thoroughfares. The curb radii shall be a
minimum of forty feet (40’) where Type A, B, and C thoroughfares intersect with Type A and
B thoroughfares. The curb radii at all other intersecting streets shall be a minimum of thirty
feet (30’). Larger curb radii may be required to accommodate fire trucks and/or commercial
trucks.
Section 2 – Thoroughfare Design Requirements May 2012 Page 2-10