FE Exam Formulas Ch. 13 Flashcards
Purpose and Variables of…
Stopping Sight Distance
V=initial speed of vehicle
tp=driver PRT (typically 2.5s)
a=vehicle rate of deceleration (typically 11.2 ft/s2)
G=roadway grade
1.47=conversion factor from mph to ft/s
f=friction factor=a/32.2
Purpose and Variables of…
Degree of Curvature
R=radius
Purpose of…
Arc and Chord Radius
Purpose of…
Total Intersection Angle of the Compound Curve
Purpose and Variables of…
Distance from PC to PT in the Direction of the Backward Tangent
R2=radius of the sharper curve
I=Total Intersection Angle of the Compound Curve
R1=radius of the sharper curve
I1=intersection angle of the flatter curve
Purpose and Variables of…
Perpendicular Distance from the Backward Tangent to PT
R1=radius of the sharper curve
R2=radius of the sharper curve
I=Total Intersection Angle of the Compound Curve
I1=intersection angle of the flatter curve
Purpose and Variables of…
Long Tangent of the Compound Curve
R1=radius of the sharper curve
R2=radius of the sharper curve
I=Total Intersection Angle of the Compound Curve
I1=intersection angle of the flatter curve
Purpose and Variables of…
Short Tangent of the Compound Curve
R1=radius of the sharper curve
R2=radius of the sharper curve
I=Total Intersection Angle of the Compound Curve
I1=intersection angle of the flatter curve
Purpose and Variables of…
Length of Spiral Curve
Ls=length of spiral transition curve
V=design speed
R=radius
C=rate of increase of lateral acceleration
Purpose and Variables of…
Magnitude of Centripetal Acceleration
V=vehicle speed
R=radius
an=normal acceleration
Purpose and Variables of…
Minimum Radius
emax=rate of roadway superelevation
fmax=side friction factor
Rmin=minimum radius
V=design speed
Purpose and Variables of…
Horizontal Sightline Offset
S=SSD
R=radius of the centerline of inside lane
HSO=horizontal sightline offset
Purpose and Variables of…
Law of Sines
lowercase=side length
UPPERCASE=angle
Purpose and Variables of…
Elevation of Point Vertical Curve
YPVC=elevation of PVC
G1=grade of back tangent
x=horizontal distance from PVC to turning point
YPVI=elevation of point of vertical intersection
G2=grade of forward tangent
L=length of curve
Purpose and Variables of…
Tangent Offset
a=parabola constant
x=horizontal distance from PVC to turning point
Purpose of…
Difference in Grade
Purpose and Variables of…
Parabola Constant
G1=grade of back tangent
G2=grade of forward tangent
L=length of curve
Purpose and Variables of…
Rate of Vertical Curvature
A=difference in grade
L=length of curve
Purpose and Variables of…
Tangent Offset at PVI
A=difference in grade
L=length of curve
Purpose and Variables of…
Crest Vertical Curve General Equation
L=length of vertical curve
S=sight distance
A=algebraic difference in grades
h1=height of eye above roadway surface
h2=height of object above roadway surface
Purpose and Variables of…
Crest Vertical Curve General Equation
L=length of vertical curve
S=sight distance
A=algebraic difference in grades
h1=height of eye above roadway surface
h2=height of object above roadway surface
Purpose and Variables of…
Crest Vertical Curve Standard Criteria h=3.5 ft, h2=2.0 ft
L=length of vertical curve
S=sight distance
A=algebraic difference in grades
Purpose and Variables of…
Crest Vertical Curve Standard Criteria h=3.5 ft, h2=2.0 ft
L=length of vertical curve
S=sight distance
A=algebraic difference in grades
Purpose and Variables of…
Minimum Curve Length Based on Headlight Sight Distance
L=length of vertical curve
S=sight distance
A=algebraic difference in grades
Purpose and Variables of…
Minimum Curve Length Based on Headlight Sight Distance
L=length of vertical curve
S=sight distance
A=algebraic difference in grades
Purpose and Variables of…
Sight Distance on a Sag Vertical Curve Under
an Overhead Structure
L=length of vertical curve
S=sight distance
A=algebraic difference in grades
h1=height of eye above roadway surface
h2=height of object above roadway surface
Purpose and Variables of…
Sight Distance on a Sag Vertical Curve Under
an Overhead Structure
L=length of vertical curve
S=sight distance
A=algebraic difference in grades
h1=height of eye above roadway surface
h2=height of object above roadway surface
Purpose and Variables of…
Minimum Curve Length Based on Riding Comfort
L=length of vertical sag curve
A=algebraic difference in grades
V=design speed
Purpose and Variables of…
Volume Using Average End Area Method
L=length of vertical sag curve
A=algebraic difference in grades
V=Volume
Purpose and Variables of…
Prismoidal Method
L=length of vertical sag curve
A=algebraic difference in grades
V=Volume
Purpose and Variables of…
Pyramidal Method
L=length of vertical sag curve
A=algebraic difference in grades
V=Volume
Purpose and Variables of…
Intersection Sight Distance
Vmajor=design speed
tg=time
Purpose and Variables of…
Structural Number Equation
SN=Structural Number
ai=layer coefficient
Di=thickness of layer
Purpose and Variables of…
Traffic Growth Factors
G=growth factor
g=annual growth rate
n=analysis period in years
Purpose and Variables of…
Intersection Crash Rate
RMEV=rate per million entering vehicles
A=number of crashes
V=ADT*365
Purpose and Variables of…
Roadway Segment Crash Rate
RMVM=rate per 100 million vehicle miles
A=number of crashes
VMT=vehicle miles traveled
Purpose and Variables of…
Crashes Prevented
CP=crashes prevented
N=number of present-day crashes
Purpose of…
Crash Reduction
Purpose and Variables of…
Free Flow Speed
BFFS=base free flow speed (default 75.4 mph)
fLW=reduction in FFS
fRLC=adjustment factor
TRD=total ramp density
Purpose and Variables of…
Traffic Flow
V=design speed
PHF=peak hour traffic
N=number of present day crashes
fHV=heavy vehicle adjustment factor
Purpose of…
Heavy Vehicle Adjustment Factor
Purpose and Variables of…
Time Allocation for the Yellow Interval
y=length of yellow interval
t=driver reaction time
a=deceleration rate
G=percent grade (+uphill,-downhill)
v=vehicle approach speed
Purpose and Variables of…
All-Red Interval
W=width of intersection
l=length of vehicle
v=vehicle approach speed
Purpose and Variables of…
Average Time Spent Waiting
mu=departure rate
rho=utilization factor
lamda=arrival rate
Purpose and Variables of…
Number of Trips that are Produced in Zone i and Attracted to Zone j
Pi=total number of trips produced in zone i
Aj=number of trips attracted to zone J
Fij=a value that is an inverse function of travel time
Kij=socioeconomic adjustment factor for interchange ij
Purpose and Variables of…
Utility Function
Ui=utility of mode i
K=constant
beta and delta=relative weights each service variable
Ci=trip cost for mode i
Ti=travel time for mode i
Purpose and Variables of…
Probability that users with utility values Ui will select mode i
Ui=utility of mode i
n=number of modes being considered
