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For updated version, please click onhttp://ocw.ump.edu.myHighway & Traffic EngineeringSPOT SPEED STUDIESbyPn. Azlina binti IsmailandDr.Intan Suhana binti Mohd RazelanFaculty of Civil Engineering & Earth Resourcesazlinai@ump.edu.my
Chapter DescriptionAimsThis chapter has presented students on the basicunderstanding on spot speed studies.Expected Outcomes Identify method associated with spot speedstudies Analyze speed data for specific application
Contents Introduction Methods in conducting Spot Speed Study Spot speed study analysis and datapresentation
Introduction Speed Definition - Distance travelled by a vehicleduring a unit of time and expressed in km/hr Used to describe the quality of journey and theperformance of road network in accommodatingtraffic demand Spot speed study definition - speed of traffic at onepoint or spot on a traffic way (instantaneous speed).SPOT SPEED STUDIES by Azlina Ismail
Spot Speed Study Purposes: Establishing the speed zone of new or existingspeed limit or enforcement practices. To determine speeds at the problem locations; tovalidate whether speeds are too high For traffic operation and control;- to establish speed limits- to determine safe speeds at curves Establishing speed trends at the local, state andnational level to assess effectiveness of speedlimit policy.SPOT SPEED STUDIES by Azlina Ismail
Locations For Spot Speed Studiesi.Speed Trend Locations:– Straight, level, open sections of rural highways– Midblock locations on urban streetsii. Representative locations of different trafficconditions on a highway for basic data surveyiii. Problematic locations (Specific trafficengineering problem ):– High accident frequency purposes– At points where the installation of traffic signalsfacility may be necessarySPOT SPEED STUDIES by Azlina Ismail
Factors effect spot speed studies: Driver - Age, Gender, motive of the journey,distance of his trip; Vehicle - type, age, weight, manufacturer andhorse power; Roadways and environment - the graphicallocations, grade, sight distance, no. of lanes,spacing of intersections; including time of dayand weather Traffic – heavy or less volume, density, passingmovements, speed regulations;SPOT SPEED STUDIES by Azlina Ismail
Methods in conducting Spot Speed StudyManual methods: To observe the time required by a vehicle to cover a shortdistance. Two reference points are located at a roadway at a fixed distanceapart. Observer starts and stops a stopwatch as vehicle enters and leftthe test section. It is most uncomplicated way. Disadvantage because of parallax effect.(refer following figure)SPOT SPEED STUDIES by Azlina Ismail
Methods in conducting Spot Speed StudyParallax Error IllustratedSPOT SPEED STUDIES by Azlina Ismail
Function of Roads in Rural Area Automatic method (radar meter detector):- Using reflected waves of very high frequency is directedfrom the radar speed meter to the moving vehicle.-The waves which is directly measurable is proportional to thespeed at which the vehicle is moving.- The limitation of radar meter are: The accuracy is varies, they are generally 1-2 mi/h. The drivers might be slowing down, this affected theresults. A good measurement angle must be acquired. Multilane traffics are difficult to studies. In heavy traffics, it is impossible to record speed of eachvehicles.SPOT SPEED STUDIES by Azlina Ismail
Data Presentation & AnalysisSPOT SPEED STUDIES by Azlina Ismail
Graphical PresentationFrequency histogram of observed vehicles' speedsSource: Figure 4.4, Garber and Hoel (2002).SPOT SPEED STUDIES by Azlina Ismail
Graphical PresentationFrequency distribution curve of observed vehicles' speedsSource: Figure 4.5, Garber and Hoel (2002).SPOT SPEED STUDIES by Azlina Ismail
Graphical PresentationFrequency Cumulative Curve of observed vehicles' speedsSource: Figure 4.6, Garber and Hoel (2002).SPOT SPEED STUDIES by Azlina Ismail
Statistical Analysisi.Arithmetic mean speed- is the average speed of all observed vehiclesfv X nwhere ;f frequency of observation in the particular groupv mean speed of each groupn number of observationsSPOT SPEED STUDIES by Azlina Ismail
Statistical Analysisii. Median Speed - The median speed is a middlevolume speed in the distribution whole volumeswhich is arranged in ascending order- It is also called 50th percentage speed (P50)iii. Modal speed is the speed value that occursmost frequently in a sample of spot speeds.SPOT SPEED STUDIES by Azlina Ismail
Statistical Analysis Standard deviation of speeds is a measure ofthe spread of the individual speedssd fv 2n 1 ( fv ) 2n(n 1)where ;f frequency of observation in the particular groupv mean speed of each groupn number of observationsSPOT SPEED STUDIES by Azlina Ismail
EXAMPLEThe accompanying data (Table Q2) shows spot speeds collected at Jalan Duta,Kuala Lumpur. Based on statistical method, determine the values of thefollowing:i)ii)iii)iv)Arithmetic mean speedMode speedMedian speedStandard deviationSPOT SPEED STUDIES by Azlina IsmailSpeed Class(km/hr)10 – 14.915 – 19.920 – 24.925 – 29.930 – 34.935 – 39.940 – 44.945 – 49.950 – 54.955 – 59.960 – 64.9No ofvehicles26547189564
.503109.83014.0130 – 34.9732.451053.003227.157371.01835 – 39.9137.451402.50337.451402.50340 – 44.9842.451802.003339.614416.0245 – 49.9947.452251.503427.0520263.5250 – 54.9552.452751.003262.2513755.0155 – 59.9657.453300.503344.719803.0260 – 282.1SpeedNo ofMeanclassvehicles, fspeed, V(km/hr)10 – 14.9215 – 19.9620 – 24.9525 – 29.957SPOT SPEED STUDIES by Azlina Ismail
References Nicholas J.Garber and Lester A. Hoel, Traffic & HighwayEngineering 3rd Edition Brooks Cole 2002 Roger P. Roess, Elena S. Prassas and William R. McShane,TRAFFIC ENGINEERING 3rd Edition, Pearson EducationInternational, 2004.
Nicholas J.Garber and Lester A. Hoel, Traffic & Highway Engineering 3rd Edition Brooks Cole 2002 Roger P. Roess, Elena S. Prassas and William R. McShane, TRAFFIC ENGINEERING
