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How can I come up with a traffic growth factor?
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Source：Internet Author：Unknow Pubdate：2010-03-06
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Gombya (Structural)
12 Jan 10 9:10
I have traffic data (traffic counts etc) and i have been told to do traffic forecasting but i don't know how to get the growth factor. Please help me out.
Debaser (Civil/Environme)
12 Jan 10 12:11
Your national roads authority (e.g. UK Highways Agency) should have traffic growth projections for sometime into the future, for use in modelling (of both traffic flows and transport economics). They would be my first stop.
CarlB (Civil/Environme)
12 Jan 10 18:18
If city road(s), your loacal government probably has some growth projections, which will likely vary by location depending on available developable land.
francesca (Civil/Environme)
12 Jan 10 20:27
字串7
I don't envy anyone trying to project traffic growth based on data from 2007-present. Traffic declined consistently in the US over that period, the first decline in US history.
rhinoconsulting (Civil/Environme)
21 Jan 10 1:07
I generally get past traffic count data either stationary counts, intersection counts and so forth and extrapolate with a bit of contingency.
If the data suggests a past growth factor of a compounding 2-3%, I might use 3.5% to be on the safe side (depending on potential development impacts of surrounding areas, new road planning jobs etc).
Traffic's a really hard thing to predict, with forecasting I usually predict to 10 and 20 year horizons. Even at 20 year horizon periods it's hard to predict traffic as different developments will impact differently, and traffic will change their routes to suit the best travel times.
Basically just justify your assumptions and you should be sweet!
字串5
francesca (Civil/Environme)
22 Jan 10 20:02
I suggest you read up on the ITE manuals/guidelines for traffic forecasting and talk to your reviewing agency to determine their policies.
If you have past traffic counts, then use that data with caution. Randomly adding your own "factor of safety" to what the data shows is not scientifically sound. Either use what your data tells you or find data to support your assumptions.
If the local authority has a traffic model, that is a good start. Traffic models account for planned population and employment changes, but are usually too aggregate to be used alone. Still, they are useful for extrapolating 20 or 30 years into the future.
Do not just look at immediate roads, look in your project vicinity, and look for reasons for changes in traffic. E.g. if traffic fluctuates by 10-20% one year, find out why. Some roads have permanent count stations giving good "average" AADTs, whereas other roads have stations that are counted one day a year. 字串7
If you're "not from 'round here" talk to people who are. Was the nearby interstate under construction that year that there was 15% more traffic? Did a factory close the year that traffic declined by 5%? Is the local area at full build-out? When did it get there? These things affect your historical traffic growth, explain anomalies and support adjustments.
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