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Speed is an important transportationconsideration relates to safety,time, convenience & economics.Spot Speed Study - Average speedof vehicles passing a point, or thetime mean speed.

Conducted to estimate thedistribution of speeds of vehicles in astream of traffic at a particular location on a highway.

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Speed Limit Studies

Establishing Speed Trends

Specific Design Applications

Specific Control ApplicationsInvestigations of High Accidents

Locations.

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M anual Stopwatch

Automatic R oad Detectors Doppler-Principle M eters

Electronic-Principle Detectors

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Stopwatch method is aquick and inexpensivemethod for collecting

speed data.Spot speeds may beestimated by manuallymeasuring the time it takesa vehicle to travel betweentwo defined points on theroadway.

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As the front wheels of a vehicle cross amark at the beginning of thepredetermined study length, theobserver starts the stopwatch.The watch is stopped when the vehiclesfront wheels pass a reference line in frontof the observer

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R adar M eter Commonly used device for directlymeasuring speeds in spot speed studies.M ay be hand-held, mounted in avehicle, or mounted on a tripod.

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Pneumatic R oad Tubes

Used for longer data collection timeperiods than those of either thestopwatch or radar meter method.

Using this method, pneumatic tubes areplaced in the travel lanes and areconnected to recorders located at theside of the road.

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The collected data are downloadedfrom the recorder to a laptop computer or portable disk drive in the field.

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Spot Speed Study Data Collection Form

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The speed data can be presented by

Frequency Distribution Table

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Speed Class(m/sec)

Class M idValue, (ui)

Class Frequency(No. of

observation inclass) fi

fi ui

Percentage ofobservation in class

(%)

Cumulativepercentage of all

observation (%)fi (ui - )

34

35.9 35 2 70 2.3 2.30 420.50

36

37.9 37 3 111 3.5 5.80 468.75

38

39.9 39 2 78 2.3 8.10 220.30

40

41.9 41 5 205 5.8 13.90 361.25

42

43.9 43 3 129 3.5 17.40 126.75

44

45.9 45 11 495 12.8 30.20 222.75

46

47.9 47 4 188 4.7 34.90 25.0048

49.9 49 18 882 21 55.90 9.00

50

51.9 51 7 357 8.1 64.00 15.75

52

53.9 53 8 424 9.3 73.30 98.00

54

55.9 55 11 605 12.8 86.10 332.75

56

57.9 57 5 285 5.8 91.90 281.25

58

59.9 59 2 118 2.3 94.20 180.50

60

61.9 61 2 122 2.3 96.50 264.5062

63.9 63 2 126 2.3 98.80 364.50

64

65.9 65 1 65 1.2 100.00 240.25

Total 86 4260 3631.8

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Spot Speed Study is consideredimportant to be carried out which is

useful in making many speed-relateddecisions such as determiningappropriate speed limits, establishingspeed trends, etc.

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Thank You!