MODULE 5: Traffic Flow Flashcards
Is the study of interactions between travelers (humans and vehicles) and infrastructures.
Traffic Flow
It is the arithmetic mean of speed of all vehicles passing a point during a specified interval of time.
Time Mean Speed (ππ‘)
Formula for Time Mean Speed
ππ‘ = βππ / π
Is the harmonic mean of speed of vehicles occupying a relatively long section of street or highway at a given instant.
Space Mean Speed (ππ )
Formula for Space Mean Speed if the distance is same or constant but different times
ππ = ππ / βπ‘π
Formula for Space Mean Speed for different distances but same time
ππ = βπ / ππ‘π
Formula for variance
ππ‘ = ππ + (πΒ² / ππ )
Formula for Standard Deviation
π = βvariance
The time mean speed will always be _____ than space mean speed
greater
The number of vehicles per unit time passing a point in space and is usually expressed in vehicles per hour
Flow (q)
The number of vehicles counted in a specified time interval
Volume (q)
Ratio of the total hourly volume to the maximum rate of flow within the hour
Peak Hour Factor (PHF)
Formula for Peak Hour Factor
PHF = Hourly Volume / (60/15)*(Highest Volume)
The number of vehicles per unit distance occupying a section of a roadway at a given instant time and is usually measured in vehicles per mile or per kilometer.
Density
Formula for Density
K = n/d
The ratio of the sum of the lengths of the vehicles to the length of the road section in which those vehicles are present.
Occupancy
Formula of Occupancy
O = βL / π
Rate of change of distance with respect to time
Speed
The reciprocal of speed
Rate of travel
The time elapsed between common points on successive vehicle
Headway (H)
The time elapsed between the rear of one vehicle to the front of the next vehicle
Gap (g)
The distance between common points on successive vehicle
Space (S)
The distance between the rear of one vehicle to the front of the next vehicle
Clearance (c)
Formula for headway
H = 1/q
Formula for gap
G = H - Vehicle Length (in time)
Formula for Space
S = 1/k
Formula for clearance
S - Vehicle Length (in distance)
The average speed that a motorist would travel if there were no congestion
Free Flow Speed
The maximum density under free flow
Critical density (kc or Do)
The maximum density under congestion
Jam Density (kj or Dj)
The maximum number of vehicles that can pass a given point on a lane or roadway for one hour
Maximum Capacity (qcap)
Formula for Jam Density
Kj = 4qcap / πf
Another formula to solve for density
q = Kπf - (πf/Kj) (KΒ²)
