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Md. Tahmidul Islam Farabi06 02 03 0314th Year 2nd SemesterDepartment of Civil Engineering

REPORT ON Traffic Speed Study

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INTRODUCTION

Speed is an important transportation consideration because it relates to safety, time, comfort, convenience, and economics. Spot speed studies are used to determine the speed distribution of a traffic stream at a specific location. The data gathered in spot speed studies are used to determine vehicle speed percentiles, which are useful in making many speed-related decisions. Spot speed data have a number of safety applications:

1. Determining existing traffic operations and evaluation of traffic control devices

a. Evaluating and determining proper speed limitsb. Determining the 50th and 85th speed percentiles c. Evaluating and determining proper advisory speedsd. Establishing the limits of no-passing zonese. Determining the proper placements of traffic control signs and markingsf. Setting appropriate traffic signal timing

2. Establishing roadway design elements

a. Evaluating and determining proper intersection sight distanceb. Evaluating and determining proper passing sight distancec. Evaluating and determining proper stopping sight distance

3. Assessing roadway safety questions

a. Evaluating and verifying speeding problemsb. Assessing speed as a contributor to vehicle crashesc. Investigating input from the public or other officials

4. Monitoring traffic speed trends by systematic ongoing speed studies5. Measuring effectiveness of traffic control devices or traffic programs,

including signs and markings, traffic operational changes, and speed enforcement programs

For a spot speed study at a selected location, a sample size of at least 50 and preferably 100 vehicles is usually obtained (Ewing 1999). Traffic counts during a Monday morning or a Friday peak period may show exceptionally high volumes

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and are not normally used in the analysis; therefore, counts are usually conducted on a Tuesday, Wednesday, and Thursday. Spot speed data are gathered using one of three methods: (1) stopwatch method, (2) radar meter method, or (3) pneumatic road tube method. These methods are described in this chapter in order from least expensive to most expensive. The stopwatch

Objectives:

The main objectives of the traffic speed study are below:

Capacity study

Geometry study

Accident study

Economic study

Performance study of traffic control device.

Planning & designing.

Capacity relation to speed

Highway economic studies.

Congestion studies. Planning & designing has many classes, such as

1. Traffic signal design

2. Design mood sign.

3. Parking study

4. Establishing speed limit

5. Speed zoning.

Factor Affecting in Speed:a. Road way geometric, operating and surface

condition.

b. Amount of side friction.

c. Traffic condition.

d. Time of the day.

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e. Other condition.

Method:

There are two methods are used for this method:

1. Spot speed study

2. Travel speed study

In this experiment we use the Travel speed method.

Different Types of Speed:

1. Spot speed: instantaneous speed of a vehicle at pt.

2. Running speed: Average speed while in motion.

3. Journal speed: Overall speed including stops

4. Operating speed: It is the highest overall speed at which a driver can travel on a given highway under favorable weather.

5. Free flow: driver traveling at design speed

6 Safe speeds: It is the maximum safe speed that can be maintained.

7. Design speed: 98th percentile speed is called design speed

8. Median speed: 50th percentile speed.

9. Modal speed: Speed at highest frequency.

Daily Studies:

1. To find out the location causes and duration of daily.

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2. To prescribe the remedial measures of congestion.

3. for economic equation.

4. To evaluate the performance of particular measures

5. for travel demand measurement.

Description of speed measurement method:

Stop watch method:

This method consists of timing vehicles with a hand held stop watch as they travel between two predetermined reference points that are a specific distance apart.

Using the distance between reference points and the recorded times.

Staff can calculate each vehicle’s speed.

Calculating mph is easier if the following recommended distances between reference points are used or if the average speed is below 25 mph, 88 ft, 25-40 mph, 176 ft, above 40 mph, 264 ft.

The stop watch method is the quickest and easiest but also the least accurate data collection method.

Speeds must be calculated manually and staff must be physically present to collect data.

Timers will need two stopwatches (one for backup) manual data collection forms (samples are included in handbook), measuring tape, two brightly colored reference posts and a hardhat and safety vest.

Staff should select the appropriate time of day for collecting data. For analyzing peak traffic flows, off course, speeds should be measured during peak traffic times. For assessing general speed trends or setting speed limits, off-peak measurements are more appropriate.

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The stopwatch method can be used to successfully complete a spot speed study using a small sample size taken over a relatively short period of time. The stopwatch method is a quick and inexpensive method for collecting speed data.

Travel speed:

The main theme of this work revolves around “travel speed study”.

Engineers & planners have been conducting traffic volume studies for many years.

Speed has traditionally been an input that demands modelers to adjust as necessary to improve the accuracy of the volumes forecasted by the model.

However the collection of travel speed data will be quite a bit more difficult then spot speed study because for doing it manually, greater accuracy is required.

There are other types of method such as:

1. Manual method2. Strip method3. Automatic method Rader gun method

Those are included in spot speed measure method.

1. license plate method2. Floating car method3. Elevated observer method.

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Data Collection & Analysis:

Data collection using electronic detector is simple and only requires programming the detector with the time duration over which it will measure the speed of all vehicles passing over it.During this time duration, spot speed measurement using radar meter on the other hand requires a lot of common sense in selecting which vehicle to target and time period over which the study (i.e. off peak, dark condition) should be conducted.

For example when speed study is needed to investigate a track accident problem in dark conditions at a given road, the study should be done on a sample of trucks during dark conditions on that particular road.

Spot Speed Method

Table: Spot speed of 6 types of vehicles.17, 19, 18, 20, 22, 23, 22, 24, 21, 24, 21, 22, 23, 24, 24, 25, 26, 26, 26, 28, 28, 28, 28, 27, 26, 29, 28, 27, 27, 29, 26, 28, 27, 26, 26, 25, 25, 26, 28, 29, 26, 25, 27, 26, 28, 29, 25, 32, 30, 30, 32, 30, 31, 31, 32, 33, 33, 33, 34, 33, 32, 31, 30, 30, 31, 33, 32, 31, 33, 32, 34, 34, 34, 34, 31, 32, 31, 32, 32, 33, 34, 34, 33, 32, 31, 33, 34, 34, 31, 32, 32, 32, 33, 33, 44, 40, 42, 42, 42, 42, 40, 40, 41, 43, 43, 43, 44, 44, 42, 44, 44, 41, 42, 43, 36, 35, 35, 35, 37, 36, 38, 38, 38, 36, 35, 36, 35, 37, 37, 37, 38, 39, 39, 37, 39, 37, 36, 36, 35, 35, 39, 45, 47, 48, 49, 48, 51, 53.

Speed range

No of vehicle

( f )

Mid speed( v )

% of frequency

Cumulative % of frequency

10-15 0 12.5 0 0

16-20 4 17.5 2.70 2.70

21-25 16 22.5 10.81 13.51

26-30 32 27.5 21.12 35.13

31-35 49 32.5 32.69 68.32

36-40 23 37.5 18.12 86.44

41-45 18 42.5 15.54 95.3

46-50 4 47.5 2.70 98.65

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Mid speed vs % of frequency

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60

Mid speed

% o

f fr

equ

enc

y

Mid speed vs % of frequency

51-55 2 52.5 1.35 100

Total 148 100 100

Mid speed vscumulative frequency

0

20

40

60

80

100

120

0 10 20 30 40 50 60

Mid freq

Cu

mu

lati

ve %

Mid speed vscumulative frequency

Modal Speed = 34 m/h

Average Speed = 33 m/h

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Design Speed = 38 m/h

Operating Speed = 48 m/h

Upper Speed Limit = 38 m/h

Lower Speed Limit = 26 m/h

Travel speed method:

Length = 0.904 Km

∑ Vt

n=27 .06+27 .06

2=27 .06

V s=ns

∑ t=2x 0 .904

460

=27 .12

δ s2={√∑ (x−x )

2

n−1 }2

Vehicle types

Registration plate

Time

us

Timeds

Travel Time

Travel Speed(kmph)

LV 3409 12:05 12:07 2 27.06B 4897 12:00 12:04 4 13.53

SPT 8789 12:15 12:21 6 9.02LV 8359 11:44 11:47 3 18.04LV 1718 11:47 11:50 3 18.04AR 1441 12:01 12:03 2 27.06AR 790 12:05 12:07 2 27.06

SPT 5500 11:50 11:54 4 13.53LV 1711 11:51 11:54 3 18.04LV 5223 11:40 11:42 2 27.06LV 3826 11:41 11:43 2 54.12MC 1423 12:02 12:05 3 18.04

∑Tra .time=¿¿36 ∑Tra . speed=¿¿270.6

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Auto Rickshaw:

n=2

∑ t=4min

∑V t=270.6 Kmph

V t=∑ V

t

n=27 .06+27 .06

2=27 .06≈27.1

V s=ns

∑ t=2x 0 .904

460

=27 .12

V s+δ s

2

V S

=27.12+0=27.12

V t=V s+δ s

2

V S

Light Vehicle:

n=6

∑ t=14min

x x ( x−x )2

27.0618.0418.0418.0427.0654.12

27.0627.0627.0627.0627.0627.06

081.3681.3681.360732.27

∑ (x−x )2=976.27

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δ s2={√∑ (x−x )

2

n−1 }2

=(√976.275 )

2

=39.05

V s+δ s

2

V S

=23.25+ 39.0523.25

=26.7

V t=∑ V

t

n=27 .06 x2+18.04 x 3+54.2

6=27

V t=V s+δ s

2

V S

Calculation of Delay:

From least spot of AR= 17mph

Travel time = 2

Delay = Travel Time – Least Spot Speed

ADT ( SL- NM ) = % of AR = 27.04

No of AR = 174

Total Dealy = 2610 Hr/Day

Determination of LOS :

SL – NM :

G4=12:00 – 1:00=18.71x170=20180

G5=01:00 -2:00=16.71x160=2675.6

G6=2:00 -3:00=14.74x250=3685

ADT=G 4+G 5+G 63

=8846.87

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DHK=1.15X8846.87

=10143.9

VC

= 368510143.9

=0.36

Conclusion:

For this experiment we have collected data from science lab to new market in Dhaka. We have done the experiment in a group. By calculating data we found some results. From the analysis of given data, we get, Modal speed = 33mph, Pace speed = 24.5 - 34.5mph, Design speed = 38mph, Operating speed = 48 mph and Lowest Speed limit = 26mph.Such result helps in developing highway and transportation plans and performing economic analysis. Studies based on this analysis are very helpful for engineers in suggesting necessary steps required to reduce the number of road accidents.

Reference:Books:

a. Highway Engineering: Paul H. Wrightb. Transportation lecture sheet of coarse no.351

Web Sites:

o http://www.traffic speed study .como http://www.Traffic survey.como http:// traffic road way system.com