Lecture 2 - Traffic Flow Fundamentals

Question 1

involves the development of mathematical relationships among the primary elements of a traffic stream: flow, density and speed

Answer 1

Traffic flow theory

Question 2

These relationships help the traffic engineer in ____, _____, and ______ the effectiveness of implementing traffic engineering measures on a highway system

Answer 2

planning, designing and evaluating

Question 3

is used in design to determine adequate lane lengths for storing left-turn vehicles on separate left-turn lanes, the average delay at intersections and freeway ramp merging areas, and changes in the level of freeway performance.

Answer 3

Traffic flow theory

Question 4

simulation where mathematical algorithms are used to study the complex interrelationships that exist among the elements of a traffic stream or network and to estimate the effect of changes in traffic flow on factors such as crashes, travel time, air pollution, and gasoline consumption.

Answer 4

Traffic flow theory

Question 5

a graph that describes the relationship between the location of vehicles in a traffic stream and the time as the vehicle progress along the highway

Answer 5

Time space diagram

Question 6

flow occurring at long sections of road where vehicles are not required to stop by any cause external to the traffic stream

Answer 6

Uninterrupted Flow

Question 7

flow occurring at intersections or driveways where vehicles are required to stop by any cause outside the traffic stream – such as traffic signs (STOP or YIELD), traffic signal lights, etc.

Answer 7

Interrupted flow

Question 8

equivalent hourly rate at which vehicles pass a point on a highway during a time period less than 1 hour

Answer 8

Flow

Question 9

equivalent hourly rate at which vehicles pass a point on a highway during a time period less than 1 hour

Answer 9

Density or Concentration

Question 10

is the rate of motion; distance travelled by a vehicle during a unit of time

Answer 10

Speed

Question 11

the average of all vehicular speed at any given time

Answer 11

Mean speed

Question 12

is the arithmetic mean of the speeds of vehicles passing a point on a highway during an interval of time

Answer 12

Time mean speed

Question 13

is the harmonic mean of the speeds of vehicles passing a point on a highway during an interval of time

Answer 13

Space mean speed

Question 14

is defined as the time interval between passage of consecutive vehicles at a specified point on the road with a unit of time per vehicle

Answer 14

Time headway

Question 15

is the distance between two vehicles measured from the front bumper of a vehicle to that of another

Answer 15

Spacing / Space headway

Question 16

The fundamental traffic equation relating flow, density, and space mean speed is given as:

Answer 16

𝐹𝑙𝑜𝑤 = 𝑑𝑒𝑛𝑠𝑖𝑡𝑦 × 𝑠𝑝𝑎𝑐𝑒 𝑚𝑒𝑎𝑛 𝑠𝑝𝑒𝑒𝑑
Or,
𝑞 = 𝑢s𝑘

Question 17

When the density on the highway is 0, the flow is ______ because there are no vehicles on the highway

Answer 17

zero

Question 18

. As the density increases, the flow____

Answer 18

also increases

Question 19

When the density reaches its maximum the flow must be 0, because vehicles will tend to line up ________

Answer 19

end to end

Question 20

As the number of vehicles in a road section increases, there is a _______ in speed, in particular, a continuous increase in flow will result in a continuous decrease in speed.

Answer 20

linear decrease

Question 21

space mean speed at zero density

Answer 21

Free flow speed

Question 22

density at zero space mean speed

Answer 22

Jam density

Question 23

he hypothesized that a linear relationship existed between speed and density, which he expressed as follows:

Answer 23

Greenshield’s model