Effects of uncertainty in speed-flow curve parameters on a large-scale model: case study of the Danish national model

Manzo, Stefano, Nielsen, Otto Anker and Prato, Carlo Giacomo (2014) Effects of uncertainty in speed-flow curve parameters on a large-scale model: case study of the Danish national model. Transportation Research Record, 2429 2429: 30-37. doi:10.3141/2429-04


Author Manzo, Stefano
Nielsen, Otto Anker
Prato, Carlo Giacomo
Title Effects of uncertainty in speed-flow curve parameters on a large-scale model: case study of the Danish national model
Journal name Transportation Research Record   Check publisher's open access policy
ISSN 0361-1981
2169-4052
ISBN 9780309295239
Publication date 2014
Year available 2014
Sub-type Critical review of research, literature review, critical commentary
DOI 10.3141/2429-04
Open Access Status Not Open Access
Volume 2429
Issue 2429
Start page 30
End page 37
Total pages 8
Place of publication Washington, DC, United States
Publisher U.S. National Research Council * Transportation Research Board
Language eng
Abstract Uncertainty is inherent in transport models and prevents the use of a deterministic approach when traffic is modeled. Quantifying uncertainty thus becomes an indispensable step to produce a more informative and reliable output of transport models. In traffic assignment models, volume-delay functions express travel time as a function of traffic flows and the theoretical capacity of the modeled facility. The VS. Bureau of Public Roads (BPR) formula is one of the most extensively applied volume delay functions in practice. This study investigated uncertainty in the BPR parameters. Initially, BPR parameters were estimated by analyzing observed traffic data related to the Danish highway network. Then, BPR parameter distributions were generated by using the resampling bootstrap technique. Finally, the generated parameter vectors were used to implement sensitivity tests on the four-stage Danish national transport model. The results clearly highlight the importance to modeling purposes of taking into account BPR formula parameter uncertainty, expressed as a distribution of values rather than assumed point values. Indeed, the model output demonstrates a noticeable sensitivity to parameter uncertainty. This aspect is evident particularly for stretches of the network with a high number of competing mutes. Model sensitivity was also tested for BPR parameter uncertainty combined with link capacity uncertainty. The resultant increase in model sensitivity demonstrates even further the importance of implementing uncertainty analysis as part of a robust transport modeling process.
Keyword Uncertainty
Bureau of Public Roads (BPR) formula
BPR parameters
Danish national transport model
Model sensitivity
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Critical review of research, literature review, critical commentary
Collection: School of Social Science Publications
 
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