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Spot Speed Study.

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Presentation on theme: "Spot Speed Study."— Presentation transcript:

1 Spot Speed Study

2 Before anything else Read the manual carefully. It is your homework
What is covered in the following slides is just general

3 General The data is to be used for assessing general speed trends and for setting speed limits. The equipment for our data collection procedure is a hand-held radar. Radar usage Radar checkout

4 Data Collection Name of the safety officer Choose section of road
Not close to intersection Off-peak period during daylight hours on a typical weekday Hide  I will contact Police to cover you

5 Data collection form

6 Data analysis What should you do with the collected speeds?
What else, statistical analysis! Remember that old stuff: Mean, standard deviation,… Plus a few more things

7 Speed Statistics Average speed Speed data Grouped Not grouped
Standard deviation Variance s2 u = uj/N f(ui – u)2 s = N - 1

8 Types of Speed Measurements
Median speed The speed at the middle value in a series of spot speeds. Or, 50th-percentile speed Modal speed The speed value that occurs most frequently in a sample of speeds ith-percentile speed The spot speed below which i percent of the vehicles travel, e.g. 85th-percentile speed Pace The range of speed that has the greatest number of observations; usually 10-mph range 85% 50%

9 Frequency histogram example

10 Frequency distribution curve

11 Cumulative frequency distribution curve

12 Helping calculation table

13 Interpret and conclude
Answer questions in manual Prepare your presentation

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