Understanding crossing risk Guide 17
What FRA's predicted crossing values mean
FRA's GXAPS values are modeled annual incident estimates for the model's intended crossing-analysis uses. They do not rank crossings or predict whether a particular journey will involve an incident.
For engineers, researchers and reporters interpreting a model output.
APS2020 is a model, not an observation.
The APS2020 report describes FRA's method for estimating crossing incidents from reported conditions and history. A model output depends on its inputs and assumptions.
A predicted annual value is different from the number of reports recorded in a particular year. Do not substitute one measure for the other or describe a decimal value as a fractional event that actually happened.
Sources: FRA: APS2020 model report.
Check FRA's correction and release notices.
Read the GXAPS application's current notices before using a value in an analysis. Calculation corrections or changes to input data can affect the version you should use.
Retain the model name, observation period and source used for your analysis. If a correction affects it, document the change instead of silently replacing a cited value.
Sources: FRA: GXAPS model notices.
FRA says the values do not rank crossings.
FRA's caveat says the predictions “do not rank crossings”. Its output is not a final conclusion about present conditions.
Do not sort the Atlas into a danger list using the model. A comparison needs the agency's intended method and the other evidence relevant to the decision.
Sources: FRA: GXAPS purpose and limitations.
Engineers use models within a wider review.
A model can help frame questions about reported conditions. It does not replace a site review, current traffic information or assessment of a proposed treatment.
For a funding or engineering decision, follow the program's specified method. A state's project selection index may differ from the FRA prediction.
Sources: FRA: APS2020 model report.
Read the value beside its source and caveat.
When a matched prediction is available, the crossing page shows the value with its model and source period. An absent value is not zero.
Check the original FRA output before using it in a professional analysis. The Atlas does not add a safety rating, ranking or implied guarantee to the number.
Sources: FRA: GXAPS model notices.
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