Estimate of Flows, Growth, Stability and Counting. by ryweed Flashcards
Two types of counting methods?
1) Axle Count (preumatic tube)
2) Vehicle Count (induction tube)
How long should the count go for?
1 hour so hourly flows can be determined.
What must be done to axle counts in order to process with further calculations?
They must be converted to vehicle counts.
Three types of converting methods?
1) Visual survey
2) Vehicle classifier survey
3) Indirect survey
What is a visual survey?
- Count vehicle and axle for a few hours
- Do on weekdays when trucks are in high numbers
- This is so data is bias upwards
Whats is a vehicle classifier survey?
I dont know, you tell me?
What is an indirect survey?
Obtain axle factor from a similar site and use this to convert. This can hold error.
What has a greater error, and what is this error when comparing tube counts to loop counts?
Tube counts have the greater error.
This is about 2 - 4% ‘greater’ than loop.
What is AADT?
Annual Average Daily Traffic.
Daily traffic flow averaged over the whole year.
What is ADT?
Average Daily Traffic.
Daily traffic flow over less than a year.
What is a control station?
Site where traffic is counted for a complete week, every 1 - 2 months.
What is an Ordinary Station?
Site where traffic is counted for a complete week, 1 - 4 times per year.
What is a special station?
Site is counted for a special purpose/required.
What is a short term count?
Count less than a week.
Traffic Flow Stability.
What is local stability?
Response of the (n+1) th vehicle to change the motion of the nth vehicle.
Traffic Flow Stability.
What is asymptotic stability?
The manner in which fluctuation in motion of a vehicle is propagated along the line of vehicles following.
When does spacing between two vehicles become less stable?
As (alphaT) increases.
What does DHV mean?
Design Hourly Flow rate (veh/hr) for which a road is designed.
How do you estimate DHV?
1) Estimate the existing flow rate + traffic growth rate during design period to estimate future flow rate.
What method is used to estimate the flow rate?
Transit NZ method.
What are the temporal variation?
1) hour-hour within day.
2) day-day within week.
3) week-week, month-month within year.
4) trends in traffic growth.
