Week 3

Question 1

Traffic Engineering Studies

Answer 1

Spot-speed studies
Volume Studies
Travel-Time and Delay Studies
Accident Studies
Parking Studies
Headway/Spacing Studies
Pedestrian Studies

Question 2

Purpose of Spot Speed Data

Answer 2

• Establish parameters for traffic operation and control (i.e speed limits, speed zones, passing restrictions)
• evaluate the effectiveness of traffic control devices
• monitor the effect of speed enforcement programs

Question 3

Spot Speed Data - Key stats

Answer 3

Average speed - mean of all observed vehicle speeds

Median speed - middle value in a series of ascending order

Modal Speed - speed value that occurs most frequently

Ith percentile speed - speed value below which i percent of the vehicles travels

standard deviation of speeds - measure of spread of the individual speeds

Question 4

Spot Speed data - What is used to determine sample size of probability theory? Give an example with STD and mean speed.

Answer 4

Minimum sample size depends on precision.
-For example, if STD = 7, and mean speed =80, we can conclude 95% of all vehicles will be between 80+/- 7. NOTE, if STD equals 7, that means + AND -

Question 5

Traffic volume Studies - purpose?

Answer 5

• measurement of current demand
• establishment of traffic volume trends
• determines what the road is used for (functionality)

Question 6

Traffic volume Studies - Key indicators

Answer 6

• AADT
• ADT
• PHV (peak hourly volume) - max number of vehicles that pass a point on a highway during an hr
• VC (vehicle classification according to vehicle type)
• VKT - vehicle kilometers travel (product of traffic volume (ADT) and length of roadway in kilometers)

Question 7

Traffic volume Studies - types of count stations

Answer 7

Permanent count stations (24hrs a day, 365 days a year)

-periodic counts

Question 8

Traffic volume Studies - What are expansion factors used for?

Answer 8

To extend periodic counts. for example, hourly expansion factor is used to calculate 24 hour volume from data collected in less than 24 hours.

Question 9

Traffic volume Studies - Presentation of traffic volume data?

Answer 9

• traffic flow maps
• intersection summary sheets
• time based distribution charts

Question 10

Traffic volume Studies - Methods of speed and traffic data collection

Answer 10

Manual methods
-using mechanical counters, hand recording
Automatic methods
-using road detector
-radar based tech
-electronics (Cameras, etc)

Question 11

Travel Time and Delay Studies - Methods

Answer 11

Methods requiring a test vehicle
-floating car technique
-average speed technique
-moving vehicle technique
Methods not requiring a test vehicle
-license plate observations
-questionaires,surveys
-GPS tech

Question 12

Travel Time and Delay Studies - Floating-car and average speed technique and moving vehicle technique?

Answer 12

Floating car

• test car is driven along the test section so that the test car “floats” with the traffic
• need to make sure to pass the same # of vehicles that were passed by the test car

Average-speed
-test car driven along the section at a speed that is the average speed of the traffic stream, in the drivers opinion

Moving Vehicle Technique
u know dis