Module 2: Traffic Operations Analysis Flashcards
Define Uninterrupted Flow.
Vehicles are not interrupted by external factors such as traffic signals stop or yield signs or frequent driveway access points.
Occurs on freeways and rural highways with long segments between signalized intersections.
Define Interrupted Flow.
Vehicle flow on interrupted flow facilities is influenced by external factors such as traffic signals, stop or yield signs, or frequent uncontrolled intersections or high volume driveways. Interrupted flow occurs on urban arterials.
What three parameters are used to describe traffic stream?
Flow Rate or Volume
Speed
Density
What is the reciprocal of flow, q (vehicle/hour)?
Headway, h (sec/vehicle)
What is the reciprocal of speed, u (mile/hour)?
Travel Time, T (Sec/mile)
What is the reciprocal of density, k (vehicle/mi)?
Spacing, s (ft/vehicle)
Define Time Mean Speed (TMS).
Time mean speed is the average speed of all vehicles passing a point over a specified time period.
Define Space Mean Speed (SMS).
Space mean speed is defined as the average speed of all vehicles occupying a given section of roadway over a specific period.
Define Density.
The number of vehicles in a given length of roadway or a lane. (veh/mi)
What is the uninterrupted flow relationship with speed and density?
D= v / s
Where v = flow (veh/hr)
s = space mean speed (mi/hr)
D = density (veh/mi)
Define volume.
The number of vehicles that pass a point on a roadway, a lane or a direction of a roadway per unit of time.
How do you convert volume into flow rate?
PHF = Hourly Volume / (4* Peak 15 minute volume)
What is the purpose of a site traffic impact analysis?
To determine the needs for any improvements to the adjacent and nearby road system to maintain a satisfactory LOS, safety, and access to a proposed development.
