Assumptions:
(1) dry driving surface
(2) driver’s reaction time 1 second
(3) decleration rate 10 feet per second
(4) the driver may be going faster than the posted speed limit
Parameters:
(1) posted speed limit from 18 to 48 miles per hour
(2) gradient of the road from -4 to +4 degrees
speed for estimated speed of car to plan for =
= (posted speed limit) + 7
|
Gradient
|
Slope of Line
|
Intercept
|
|
+4 degrees
|
0.063
|
1.512
|
|
+2 degrees
|
0.070
|
1.432
|
|
0 degrees
|
0.074
|
1.550
|
|
-2 degrees
|
0.080
|
1.496
|
|
-4 degrees
|
0.084
|
1.587
|
Where:
• These equations are for straight lines. The actual lines were not straight with the exception of a gradient of -2 degrees.
An equation for estimating the slope from the gradient from -4 to +4 degrees =
= (-0.0026 * (degrees)) + 0.0742
The average intercept is 1.5164
A general equation would be
time of yellow light in seconds =
= ((-0.0026 * (gradient)) + 0.07420) * (speed to plan for)) + 1.5164
