Simulation of Traffic Flow - Density

PhD Candidate: Azdeen Najah Asst.Prof.Dr. Altan Ozkil

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Introduction:

Density (k):The number of vehicles (n) occupying a given length (l) of a lane or roadway at a particular instant.Unit of density is vehicles per kilometer (vpkm).

u

q

l

nk

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Keywords Definitions:

Free-flow speed (uf)The speed at which vehicles will travelunimpeded

Jam density (kj)The density of vehicles in stopped traffic

Capacity (qm)The maximum flow a section of roadway can maintain

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Keywords Definitions:

Density (veh/mile)

Flo

w (

veh

/hr)

kj

Jam Density

Highest flow,

capacity, qm

km

Optimal densityUncongested Flow

Congested Flow

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Flow vs. Density:

1. When density is zero, flow will also be zero, since there are no vehicles on the road.

2. When the number of vehicles gradually increases, the density as well as flow increases.

3. Increases in density beyond the point of maximum flow (qmax) results in reduction of flow.

4. When more and more vehicles are added, it reaches a saturation level where, vehicles can't move.

5. The relationship is normally represented by a parabolic curve 7

Some characteristics of flow vs. density relationship:

This is referred to as the jam density or the maximum density (kjam). At jam density, flow will be zero because the vehicles are not moving.

LOSMax. Density

Pc/km/lnAverage speed

Km/hrMax. v/c Max. Service flow rate

Pc/hr/ln

A 7 100.00 0.32 700

B 11 100.00 0.50 1100

C 16 98.40 0.72 1575

D 22 91.50 0.92 2015

E 25 88.00 1.00 2200

Source: Transportation Research Board Highway Capacity Manual. Washington, DC. National Research Council, 2010.

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Level of Service:Undivided Multilane Hw, LOS C, FFS = 100 km/hr

Standard ParametersHighway Functional Classification = Multilane Undivided

Free-Flow Speed (Uf) = 100 km/hr.

Level of Service (LOS) = C

Density (K) = 16 Veh./km/ln

Source: Transportation Research Board Highway Capacity Manual. Washington, DC.National Research Council, 2010.

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Input Data:

To solving traffic congestion problem in highway section specially at critical highway segment such as bridge, viaduct or tunnel etc.By using Microsoft Excel program to simulate and model Flow-Density relationship using random input data (Density) to get ideal output (Flow) to moderate and control uncongested flow on the specific highway segments with Level of service B or C by using the flex lanes system.

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The Aim :

Density (k),

Veh./hr./ln.

(Ranked)

INPUT

Flow (q),

Veh/km.

OUTPUT

0 0,000

1 93,750

1 93,750

2 175,000

3 243,750

3 243,750

4 300,000

4 300,000

5 343,750

6 375,000

7 393,750

7 393,750

8 400,000

9 393,750

9 393,750

10 375,000

11 343,750

12 300,000

12 300,000

13 243,750

14 175,000

15 93,750

15 93,750

16 0,000

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Control data:

Densıty (k),Veh./hr./ln.

(Random) INPUT

Flow (q), Veh./hr. OUTPUT

7 406,419

12 320,243

7 385,076

15 88,488

6 357,869

5 358,359

9 363,341

12 299,284

13 262,198

4 325,378

1 88,572

11 349,589

12 310,900

3 262,264

8 403,690

10 355,819

7 415,173

15 97,981

0 0,000

13 243,434

5 320,385

5 334,416

9 378,600

16 0,000 12

Random Inputs vs.Simulated Outputs:

According to:the system parameters and the desired outputs the inputs can be verified and validated.

Compare with ControlParabolic chart with following characteristics:At k=0, q=0 At kj=16, q=0 At km=Kj/2=8, qm=400

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The Verification & Validation:

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Example forFlex lanes systemApplication with this simulation

Image Processing Vehicle Detector:

This device detects vehicles and outputs traffic flow information such as volume, occupancy, presence, speed, classification, and queue length in multiple lanes by processing images taken by a monitoring camera installed over roads.

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Data Collection:“Traffic Density” k, veh./km/ln.

For Determine the traffic flow and capacity for any road segment we should know its functional classification, LOS, FFS and Number & width of lanes.

By using Simulation and modelling we can solve the traffic congestion problems by moderate and control the critical highway segments such as viaducts, bridges and tunnels.

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The Conclusion:

Transportation Research Board Highway Capacity Manual. Washington, DC. National Research Council, 2010.

Principles of Highway Engineering and Traffic Analysis. 3dh. Edition.

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The References:

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