Table 1
Safe Site Distance for Single-Family and Two-Family Dwelling
Access to Two-Lane Roads
| ||||||
---|---|---|---|---|---|---|
Posted Speed
(mph)
|
Required Sight Distance in Feet (measured from a vehicle
10 feet back from pavement edge)
| |||||
Grade of Road
0 to 3% Up or Down
|
Increased Sight Distance for Ascending Grade After Turning
+3% to +5%
|
Decreased Sight Distance for Descending Grade After Turning
-3% to -5%
| ||||
Left
|
Right
|
Left
|
Right
|
Left
|
Right
| |
25
|
250
|
195
|
350
|
273
|
150
|
117
|
35
|
440
|
350
|
616
|
490
|
264
|
210
|
45
|
635
|
570
|
889
|
798
|
381
|
342
|
55
|
845
|
875
|
1,183
|
1,225
|
507
|
525
|
SSSD = 1.47 VT + V230 (f+g)
|
Where:
| ||||
SSSD
|
=
|
Minimum safe stopping sight distance (feet)
| ||
V
|
=
|
Velocity of vehicle (miles per hour)
| ||
T
|
=
|
Perception time of motorist (average 2.5 seconds)
| ||
f
|
=
|
Set friction of pavement (average 0.30)
| ||
g
|
=
|
Percent grade of roadway divided by 100
|
— The shoulder slope usually varies from 0.50 inch per
foot (4%) to 0.75 inch per foot (6%). However, the shoulder slope
should be maintained when constructing the driveway.
| |
— For grade changes greater than ± 6% (D), vertical
curves at least 10 feet long shall be constructed and Length "A" shall
be increased.
| |
— Grades G2 shall be limited to
12%.
|
Minimum
|
Maximum
| ||
---|---|---|---|
W-Width
|
8 feet
|
20 feet
| |
R-Radius
|
5 feet
|
15 feet
|