Data dictionary
Artifact Title(s): Probability of Weather Events
Background
Weather is one of the seven sources of congestion on the transportation network. Weather has a two-fold effect on
roadways; influencing driver behavior and increasing the likelihood of incidents which is another source of congestion.
Data collection
Historical average probabilities were created from NWS METARS data available from WeatherUnderground.
Processing Techniques
Historical weather is available in Comma Separated Value (CSV) format for any airport in the ASOS system on a daily basis.
These CSV files contain all METARs reports for the airport and day requested. A Python (v2.7) script was written to
automate the download of all daily CSV weather files for selected airports and years, and a second script compiles all daily
files into a single CSV file containing observations from all selected years for a given airport. Once a single CSV file for each
airport was created, each file was filtered and analyzed in Microsoft Excel. There were a few issues identified with the
hourly reports that had to be fixed before calculating probabilities. First, reports occasionally report “unknown” conditions
and any field with a number is reported as “-9999”. These values were changed so that they would not be picked up as a
weather category with a capacity effect. Additionally, the compiler inserted reports from previous time periods
infrequently. This would result in a negative duration between the previous report and the next one. Any repeated reports
were removed prior to analysis.
Column Descriptions
Table 1: Column Descriptions
CSV
Column
header
title
Ingested dataset
column header title
Column Description
Units of
Measurem
ent
airport
Med Rain
Airport Code
Medium Rain
NA
Probability
Str Rain
Low Snow
LM Snow
Strong Rain
Low Snow
Low-Medium Snow
MH Snow
Medium-High Snow
H Snow
High Snow
Airport Code
Probability of having rain more than 0.1 in/h and less
than 0.25 in/h
Probability of having rain more than 0.25 in/h
Probability of having snow less than 0.05 in/h
Probability of having snow more than 0.05 in/h and
less than 0.1 in/h
Probability of having snow more than 0.1 in/h and less
than 0.5 in/h
Probability of having snow more than 0.5 in/h
SHRP 2 Reliability
Archive
1
Probability
Probability
Probability
Probability
Probability
Severe
Cold
Low Vis
Severe Cold
Probability of having temperature less than -20 C
Probability
Low Visibility
Probability
Very Low
Vis
Min Vis
Normal
Very Low Visibility
Probability of having visibility more than 0.5 mile and
less than 1 mile
Probability of having visibility more than 0.25 mile and
less than 0.5 mile
Probability of having visibility less than 0.25 mile
Probability of having Normal Weather Condition
Month of the year from 1 to 12
Hour of the day from 0 to 23
NA
NA
Month
Hour
Minimum Visibility
Normal Weather
Condition
Month of the year
Hour of the day
Probability
Probability
Probability
Acknowledgments
The analysis of weather data, data download via Python Script, and compilation of weather data base was possible through
the dedicated work of ITRE graduate students Thomas Chase and Sangkey Kim, under the supervision of Dr. Nagui Rouphail
and Dr. Bastian Schroeder at N.C. State University
SHRP 2 Reliability
Archive
2