PC wk1 - Traffic Flow Fundamentals PDF

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MONASH UNIVERSITY DEPARTMENT OF CIVIL ENGINEERING Transport and Traffic Engineering

Practical Class week 1: Traffic Flow Fundamentals The exercises in this practical class examine the variables used to characterise traffic flow and the basic relationships between those variables. These exercises draw on the material presented in the lecture slides “Traffic Flow Fundamentals 1”. You will probably need a spreadsheet such as Excel to complete these exercises, remember to bring a computer with spreadsheet software into the practical class. EXERCISE 1 An observer at the side of a road conducted a traffic survey using a stop watch to record the times when vehicles passed. The recorded values are presented below: Vehicle Number 0 1 2 3 4 5 6 7 8 9 10

Observation Time (secs) 08:00:15 08:00:21 08:00:24 08:00:29 08:00:35 08:00:42 08:00:54 08:01:06 08:01:13 08:01:22 08:01:35

Question 1: What is the average headway?

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Question 2a: Based on that average headway, what is the volume (flow in vehicles per hour) on the road? __________ Question 2b: Based on that volume, what is the density on the road? __________ Question 2c: Based on that density, what is average space headway (or spacing) on the road? __________

Traffic Flow Fundamentals and Traffic Flow Theory

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EXERCISE 2 A circular test track is 2 km in length. A traffic survey conducted beside the track measured a traffic flow of 180 vehicles/hour and a space mean speed of 60 km/h. Question 3: How many vehicles are travelling around the track?

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EXERCISE 3 Five vehicles are observed travelling along a long straight section of rural highway over a one hour period. A radar gun was used to record the speeds of the vehicles as they pass. Two of the vehicles are travelling at 100 km/h, one is travelling at 90 km/h, one is travelling at 80 km/h and the slowest is travelling at 75 km/h. We wish to determine the average speed of the traffic. Question 4: What is the average of the spot speeds?

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Question 5: Is this value the time-mean speed or the space mean speed?

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At the same time, two traffic surveyors position themselves one kilometre apart along the highway. They record the times at which these five vehicles are seen, and subtract those times to give the travel time of each vehicle over the one-kilometre distance. Assuming the above five vehicles are travelling at constant speeds, the surveyors determined how long it had taken each of the five vehicles to cover the one kilometre section of road. Question 6: Based on the average time taken to travel the one-kilometre section, what is the average speed? Question 7: Is this value the time-mean speed or the space-mean speed?

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Question 8: Are the relative magnitudes of the two average speeds as you would expect?

EXERCISE 4 Three vehicles are travelling round a circular track which is 1 kilometre in length. One vehicle is travelling at 40 km/h, another at 50 km/h and the third is travelling at 60 km/h. An observer records speeds of all vehicles passing a fixed point over a period of 6 minutes. Question 9: What is the density of the traffic on the test track? Question 10: What volume (flow in vehicles per hour) does the observer record?

Question 11: Based on the values from questions 9 and 10, what is the space-mean speed?

Question 12: What is the space mean speed, calculated as the harmonic mean of the spot speeds observed at the fixed point?

Traffic Flow Fundamentals and Traffic Flow Theory

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Question 13: What is the time-mean speed? Question 14: Are the relative magnitudes of the space-mean speed and the time-mean speed as would be expected? Question 15: Calculate the time-mean speed using the formula that uses space-mean speed and the variance of the spot speeds from the space-mean speed.

EXERCISE 5 A platoon of six vehicles was observed over a distance of 300 m on a single lane of Normanby Road, entering at Point A and departing at Point B. Vehicle 1 2 3 4 5 6

Time at Point A (sec) 0 2 3 5 6 8

Time at Point B (sec) 35 37 39 42 44 48

Question 16: Calculate the average volume, density, and mean speed for the six vehicles observed, considering the first 10 seconds at Point A as the period of observation. __________

Traffic Flow Fundamentals and Traffic Flow Theory

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