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Transferred versus local Safety Performance Functions: A geographical analysis considering two European case studies

Intini, Paolo; Berloco, Nicola; Binetti, Rita; Fonzone, Achille; Ranieri, Vittorio; Colonna, Pasquale


Paolo Intini

Nicola Berloco

Vittorio Ranieri

Pasquale Colonna


Two main approaches can be used to predict road accidents: transferring existing Safety Performance Functions (SPFs) from other areas (transferred SPFs), and developing local SPFs. Both approaches have advantages and disadvantages, and are affected by the difficult choice of predictors. Regional variables or terrain factors may lead prediction improvements. However, results from previous relevant research are contradictory and transferability assessments are mainly based on North-American experiences.

Because of these inconsistencies, this study is an attempt of providing new insights on the choice between alternative accident prediction methods by taking into account the geographic variability in the European context. In particular, it addresses three main issues: 1) it compares the prediction accuracy of transferred and local SPFs; 2) it determines the significance of regional factors in explaining safety performances, 3) it assesses the variability of results among the different contexts considered. Research questions are addressed as based on two-lane rural road sites in Italy and Scotland.

The analysis shows differences between the two countries, due to the different nature of the networks, but not within each country. Both advantages and disadvantages were highlighted in the evaluation of transferred and local SPFs. Calibration of transferred SPFs may be less demanding than their local estimation, even if they may lead to unreliable estimates when compared to comprehensive SPFs. However, locally developed SPFs may not provide more significantly reliable estimates than transferred SPFs. Segment curvature and shoulder types are statistically significant predictors in both the Italian and Scottish models, even having different importance.


Intini, P., Berloco, N., Binetti, R., Fonzone, A., Ranieri, V., & Colonna, P. (2019). Transferred versus local Safety Performance Functions: A geographical analysis considering two European case studies. Safety Science, 120, 906-921.

Journal Article Type Article
Acceptance Date Aug 7, 2019
Online Publication Date Aug 30, 2019
Publication Date 2019-12
Deposit Date Aug 9, 2019
Publicly Available Date Mar 1, 2021
Journal Safety Science
Print ISSN 0925-7535
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 120
Pages 906-921
Keywords Safety Performance Functions, Transferability, Highway Safety Manual, Regional variables, Two-lane Rural Roads
Public URL


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