U4 Spot Speed Study

TRAFFIC AND HIGHWAY ENGINEERING LAB U4 - SPOT SPEED STUDY

1.0

SECTION 10 / GROUP 10

INTRODUCTION Speed is the rate of movement of a vehicle, generally expressed in kilometers per hour. A spot

speed study is a study of traffic speed at one point or spot on a traffic way. It consists of a series or a sample of observations of the individual speeds at which vehicles are approaching an intersection or passing a point at a non-intersection location. These observations are used to estimate the speed distribution of the entire traffic stream at that location, under the conditions prevailing at the time of the study. Spot speed studies can be used to study speeds at problem locations in order to determine whether speeds are too high and if complaints received are justified, for accident analysis in order to determine the relationship of speed to accidents which may help in developing corrective measures, and for before-and-after studies in order to evaluate the effect of some change in controls or conditions. In relation with this study, there has been several complaints of vehicles speeding along the Jalan Kluang. This poses a danger to motorists, pedestrians and cyclists as there is a lot of activity in the area. Furthermore, there is plenty of right-turning movements along this stretch of road, with no storage lanes provided for right-turners. This is dangerous because the right-turners stop on the fast lane and have no protection.

2.0

OBJECTIVE

The objectives of this study are: 2.1

To determine the speed characteristics of traffic at the location.

2.2

To justify the problem of speeding at the location.

3.0

APPARATUS

3.1

Radar Gun

3.2

Forms SS1 and SS2 (Refer to Appendix)

3.3

Graph Paper (3 nos)

3.4

Safety Vest

1


4.0 4.1


PROCEDURE The road in front Taman Universiti was chosen for our spot speed study. The spot at which the speed data will be collected is identified.

4.2

The radar gun is used to measure the speed of vehicles according to their respective vehicle class – Class 1 (Motorcycles), Class 2 (Cars), Class 3 (Vans & Medium Trucks), and Class 4 (Large Trucks & Buses). [The operator of the radar gun is made sure not seen by the motorists]

4.3

All speed measurements recorded in Form SS1.

4.4

Based on Form SS1, the mean, maximum and minimum speed of vehicles is determined according to their class. The findings are commented.

4.5

The data is transferred in Form SS1 to Form SS2.

2


4.6


The following are plotted: (a) Frequency Histogram (Percentage of vehicles vs. Speed) (b) Frequency Distribution Curve (Percentage of vehicles vs. Speed) (c) Cumulative Frequency Distribution Curve (Cumulative percentage vs. Speed)

4.7

The following speed characteristics is determined: (a) Mean speed (b) Median speed (c) Mode speed (d) 85-th Percentile speed (e) Standard deviation (f) Pace

3


5.0


RESULTS & DATA ANALYSIS Form SS1 Location: Road in front Taman Universiti Date: 04 April 2013

Time: 8:45 - 9:45 am

Weather: Windy

Sport Speed (km/h) Time

Vehicle Class 1

2

39

35

60

45

62

33

40

35

35

37

30

50

51

46

65

66

40

42

29

28

32

33

39

63

62

22

38

42

50

8:45-

9:00-

9:159:30 am

9:309.45 am

4

32

9:00 am

9:15 am

3

34

32

40

25

32

21

50

27

43

36

32

35

25

35

41

60

65

62

45

46

47

43

30

32

63

42

51

23

40

25

37

30

35

29

31

36

39

32

33

38

35

33

32

29

52

60

21

35

38

30

35

37

25

36

54

40

39

37

38

42

31

67

55

23

43

41

40

42

31

23

62

34

27

41

39

32

36

28

35

36

37

37

53

26

32

43

29

33

30

37

63

50

42

43

31

42

32

25

60

33

32

44

58

4



Form SS2

Speed Class (km/h)

Class Mid value, x (km/h)

Class Frequency, f

Cumulative Frequency

fx

Percentage in Class

Cumulative Percentage

15-19

17

0

0

0

0.00

0.00

20-24

22

6

6

132

4.51

4.51

25-29

27

14

20

378

10.53

15.04

30-34

32

29

49

928

21.80

36.84

35-39

37

31

80

1147

23.31

60.15

40-44

42

22

102

924

16.54

76.69

45-49

47

5

107

235

3.76

80.45

50-54

52

9

116

468

6.77

87.22

55-59

57

2

118

114

1.50

88.72

60-64

62

11

129

682

8.27

96.99

65-69

67

4

133

268

3.01

100.00

∑fx =5276

∑Percentage

∑f=133

=100.00

5


6.0

CALCULATION

1.

From SS1,

Speed

Class

Class

Midvalue,

(km/h)

x (km/h)


Class Frequency, f

fx

Vehicle Class

Vehicle Class

1

2

3

4

1

2

3

4

f1

f2

f3

f4

f1 x

f2 x

f3 x

f4 x

15-19

17

0

0

0

0

0

0

0

0

20-24

22

0

6

0

0

0

132

0

0

25-29

27

2

5

5

2

54

135

135

54

30-34

32

7

4

2

16

224

128

64

512

35-39

37

11

3

5

12

407

111

185

444

40-44

42

4

7

7

4

168

294

294

168

45-49

47

1

1

3

0

47

47

141

0

50-54

52

2

6

1

0

104

312

52

0

55-59

57

0

2

0

0

0

114

0

0

60-64

62

0

11

0

0

0

682

0

0

65-69

67

0

4

0

0

0

268

0

0

27

49

23

34

1004

2223

871

1178

∑=

Mean speed = where f = frequency of observations in the particular class x = mid-point of each class n = total number of observations = ∑f

Vehicle Class 1 (Motorcycles) Mean speed

=

= 1004 / 27 = 37.19 km/h

Maximum speed

= 51 km/h

Minimum speed

= 25 km/h

6



Vehicle Class 2 (Cars) Mean speed

=

= 2223 / 49 = 45.37 km/h

Maximum speed

= 67 km/h

Minimum speed

= 21 km/h

Vehicle Class 3 (Vans & Medium Trucks) Mean speed

=

= 871 / 23 = 37.87 km/h

Maximum speed

= 50 km/h

Minimum speed

= 27 km/h

Vehicle Class 4 (Heavy Trucks & Buses) Mean speed

=

= 1178 / 34 = 34.65 km/h

Maximum speed

= 44 km/h

Minimum speed

= 28 km/h

Comment: From the data collected, we have calculated the mean speed, as well as identified the maximum speed and the minimum speed for each class of vehicles. The mean speed for class 1 (Motorcycle) is 37.19 km/h, class 2 (Cars) is 45.37 km/h, class 3 (Vans & Medium Trucks) is 37.87 km/h and class 4 (Heavy Trucks and Buses) is 34.65 km/h.

Cars have the highest mean speed is which is 45.37 km/hr. Due to the speed limit of the road was 60 km/hr , this caused many car drivers driving below the speed limit. The mean of all the classes of vehicles is average because there are traffic light nearby and university at beside of the road. Driver will need time to speed up and have to lower down the speed when near university area.

However, of all the class of vehicles, we identified the highest of maximum speed of 67km/h, which is already over the speed limit of the road of 60km/h. This was dangerous for all either motorist, pedestrians and cyclist.

Therefore, body protection and storage lane provides are needed in reducing and preventing road accident to occur.

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2.


From SS2,

(a) Median Speed

The median can be determined from the cumulative frequency distribution curve. From the cumulative frequency distribution curve, the median speed is 37.5 km/h. th

There are 133 vehicles in total. So the median will be the 67 vehicle. th

According to cumulative frequency of form SS2, the 67 vehicle was fall in the speed class 35 39 km/h. By using the formula, Median speed =

where L=lower limit of the class in which the median class lies. n= total number of observations =cumulative number of observation up to the lower limit of the class in which the median lies =number of observations in the class in which the median lies. C=speed interval of the group.

Median speed

=

= = 37.32 km/h

8



(b) Mean Speed

By using the formula, Mean speed =

where f = frequency of observations x = mid-point of each class n = total number of observations = ∑f Mean speed

= = 5276 / 133 = 39.67 km/h

(c) Mode Speed

From the Frequency Histogram (Graph 1), the model class is 35-39 km/h. To determine the mode speed from the Frequency Histogram, by looking at the highest bar and joining its top left corner to the top left of the next bar, and the top right corner to the top right corner of the previous bar, where they intersect is the mode. Therefore, the mode speed from the grouped data are 35.5 km/h.

The mode speed also can be calculated by using the following formula:

Li is the lower limit of the modal class. fi is the absolute frequency of the modal class. fi-1 is the absolute frequency immediately below the modal class. fi+1 is the absolute frequency immediately after the modal class. ai is the width of the class containing the modal class.

= 35.4 km/h

9



th

(d) 85 Percentile Speed The speed at or below which 85 percent of the motorists drive on a given road unaffected by slower traffic or poor weather. P85 = 52.0 km/h (e) Standard Deviation The description of central tendency is not sufficient to define a distribution, therefore a measure of dispersion or spread is required. Standard Deviation = where f = frequency of observations x = mid point of each class n = total number of observation = ∑f

Speed Class

Class Mid

(km/h)

value, x (km/h)

15-19

2

Class Frequency, f

fx

fx

17

0

0

0

20-24

22

6

132

2904

25-29

27

14

378

10206

30-34

32

29

928

29696

35-39

37

31

1147

42439

40-44

42

22

924

38808

45-49

47

5

235

11045

50-54

52

9

468

24336

55-59

57

2

114

6498

60-64

62

11

682

42284

65-69

67

4

268

17956

∑f=133

∑ f x =5276

∑ f x =226172

2

10


Standard Deviation


=

=

= 11.31 km/hr

Alternative method to estimate the standard deviation: Estimated standard deviation = where P85 = 85th Percentile Speed and P15 = 15th Percentile Speed From the Cumulative Frequency Distribution Curve (Graph 3), P85 = 52.0 km/h P15 = 29.5 km/h Standard Deviation =

= 11.25 km/h

(f) Pace Pace is the 10 km/h range in speed in which the highest number of observation was recorded. From the Frequency Distribution Curve (Graph 2), the pace is 32 - 42 km/h and approximately 45% of the vehicles are in pace.

Comment: According to the calculation, our median speed is about 37.5 km/h, the mean is 39.67 km/h and the mode is 35.5 km/h. The standard deviation is about 11.30 km/h. From the graph of cumulative frequency th

distribution curve , we found out that the 85 percentile speed is 52.0 km/h. This speed indicates the speed that most motorist on the road consider safe and reasonable under ideal conditions. And from the graph of frequency distribution curve, the pace is 32 - 42 km/h and approximately 45% of the vehicles are in pace. From the result, we are known that the heavy cars were the main vehicles which contribute an accident. So, we must take action to avoid accident. Here are suggestion and recommendations of road:

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i.


The signboards like on speed limit, overtaking and sharp bends at locations prone to accidents must be placed to caution motorist.

ii.

The cat eye should be placed to on the road to decrease the speed of vehicles on this road.

7.0 DISCUSSION From this spot speed study, we are known for traffic operation establishing speed limits, determining safe speed at approaches to intersections. The road along Batu Pahat - Kluang highway was not safe and actions must be taken to avoid any road accidents. From the finding, the mean speed, maximum speed and minimum speed of each class is determined by using form SS2. This two lane highway have a speed limit of 60km/h. Each of the mean speed of class vehicles gives the different speed. For the class 1 is 37.19 km/h, class 2 is 45.37 km/h, class 3 is 37.87 km/h and class 4 is 34.65 km/h. The highest mean speed is class 2 and the lowest mean speed is class 4. Based on the mean speed for class 2 that we found, it seems the speed is under the speed limit. This are cause by a few factor that can be influence such as, the lane is straight and there are junctions nearby, so there do not have any speed up. However, a few number of cars still exceeded the speed limit. Due to this, some drivers of other class vehicles was alert by driving carefully then slow down their vehicle speed. Base on analysis, the standard deviation of this road according our observation is 11.30 km/hr, th

and the pace is between 32 km/h to 42 km/h. The 85 percentile speed as obtained from the cumulative frequency distribution curve shown is 52.0 km/h. It is important to have a good guideline for the appropriate speed limit for that road and it indicates that the speed most of the motorists on the road to considered safe and reasonable under ideal condition.

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8.0 CONCLUSION The objectives of this survey are to determine the speed characteristics of traffic at the location and to justify the problem of speeding at the location. From this experiment, we can be concluded that section of this road cannot be considered as 100% safe at this location even though the results of the th

finding which show that mean, median, pace and 85 percentile speeds have all are under the 60 km/hr speed limit, however, there were some vehicles which over the speed limit. Therefore, actions should be taken by the government as well as the society to reduce the number of road accidents.

9.0 REFERENCES ... BFC 3082. Traffic Engineering And Safety, Second edition, Department of Geotechnical & Transportation Engineering, Faculty Of Civil & Environmental Engineering UTHM. th

... Paul H. Wright & Radnor J. Paquette; Highway Engineering (5 Edition), Georgia Institute of Technology, 1979. rd

... Nicholas J. Garber; Lester A. Hoel; Traffic & Highway Engineering (3 Edition), University of Virginia, 1995. st

... Bent Tagesen; Highway Engineering & Traffic (1 Edition), Technical University of Denmark. ... http://www.vitutor.com/statistics/descriptive/mode.html

10.0

APPENDIX

... Form SS1 and SS2 ... Graph 1: Frequency Histogram (Percentage of vehicles vs. Speed) ... Graph 2: Frequency Distribution Curve (Percentage of vehicles vs. Speed) ... Graph 3: Cumulative Frequency Distribution Curve (Cumulative percentage vs. Speed)

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U4 Spot Speed Study

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