Traffic Forecasting Accuracy Assessment Research (2020) / Chapter Skim
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Pages 37-45
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From page 37... ...
I-25 Forecasting is a challenging activity that always includes an inherent level of uncertainty, yet forecasters traditionally have been asked to provide what is called a point forecast -- usually a single estimate of the traffic volumes on a project. As provided, the point forecast is devoid of any recognition of uncertainty.
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From page 38... ...
I-26 Traffic Forecasting Accuracy Assessment Research the sample mean, the errors are based on a specified quantile of the sample (e.g., the 10th percentile, 20th percentile, and so forth)
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From page 39... ...
Using Measured Accuracy to Communicate Uncertainty I-27 2.2 Introduction to Quantile Regression Quantiles, or percentiles, are breakpoints that divide a frequency distribution into intervals with the specified probability. For example, the 5th percentile (quantile 0.05)
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I-28 Traffic Forecasting Accuracy Assessment Research In general, the quantile regression lines (lines 1, 2, 4, 5 and 6) represent estimated changes in the actual or measured volumes, based on the nth percentile of error values, given changes in forecast volume.
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From page 41... ...
Using Measured Accuracy to Communicate Uncertainty I-29 from these defaults. It is therefore preferable to compile local forecast accuracy data using the methods described in Chapter 3, and to use those data to estimate local quantile regression models as described in Chapter 4.
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I-30 Traffic Forecasting Accuracy Assessment Research Table I-2 lists the variables used in each version. This table shows forecasters a range of possible variables for their individual use.
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Using Measured Accuracy to Communicate Uncertainty I-31 unemployment for the region was 4% at the time of the forecast. After the forecast is finalized, the forecaster enters the information from Table I-4 into a spreadsheet.
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I-32 Traffic Forecasting Accuracy Assessment Research Figure I-5. Demonstration 1, quantile regression lines.
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Using Measured Accuracy to Communicate Uncertainty I-33 Figure I-6. Demonstration 2, quantile regression lines.
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