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Road safety performance measures and AADT uncertainty from short-term counts
Craig Milligan1, Jeannette Montufar2, Jonathan Regehr2
1University of Manitoba Department of Civil Engineering, E1-327, 15 Gilson Street, Winnipeg, MB, R3T 2N2, Canada; Fireseeds North Infrastructure, 200-135 Innovation Drive, Winnipeg, MB R3T 6A8, Canada.
Accident; Analysis and Prevention
|September 23, 2016
Summary
This study quantifies uncertainty in annual average daily traffic (AADT) estimates, crucial for road safety analysis. Understanding AADT error improves risk assessment for traffic safety performance measures.
Area of Science:
- Transportation Engineering
- Traffic Data Analysis
- Road Safety
Background:
- Annual Average Daily Traffic (AADT) is a key input for road safety performance measures.
- Existing awareness of AADT uncertainty is not well-quantified or incorporated into analyses.
Purpose of the Study:
- To create the first knowledge base on uncertainty in AADT estimates derived from expanding short-term counts.
- To enable improved risk analysis for road safety performance measures.
Main Methods:
- Simulated nearly 2 million short-term traffic counts over five years using data from 69 permanent traffic recorders.
- Expanded short-term counts to AADT estimates by transferring temporal data from control stations.
- Analyzed the impact of count length, number of counts, count timing (weekday/weekend), distance to control station, and AADT level on estimation errors.
Main Results:
- The mean absolute transfer error for AADT estimates was 6.7%, ranging from 5% to 10.5% across traffic patterns.
- Most errors fell between -20% and +30%.
- Error decreased with longer counts (48h vs. 24h), increased with distance to the control station, and significantly increased with higher AADT levels.
Conclusions:
- The findings provide an evidence base for risk analysis of road safety performance measures relying on AADT.
- Improved understanding of AADT uncertainty can facilitate the application of existing analytical frameworks in road safety.
