In Italy, almost half of all road crashes occur at intersections, mostly in urban areas. However in recent years the widespread conversion of at-grade intersections to roundabouts has brought many advantages in terms of safety. To assess safety benefits of this kind of intersection, transportation professionals need the powerful statistical tool known as the Safety Performance Function (SPF). To date there has been no reported application of this tool to assess the relative safety performance of Italian urban roundabouts. This paper fills that void, thanks to the availability of data sets from two Municipalities in Northern Italy. SPFs were estimated for each city with the negative binomial error distribution and then recalibrated for application in the other city using the procedure being implemented in the Highway Safety Manual. Model reliability and between-city transferability was evaluated with the Cumulative Residuals (CURE) method. To assess how the Italian roundabout safety performance functions might be used to learn lessons from differences in crash experience for similar intersections elsewhere, a comparison with models from other countries is also provided. This comparison revealed that Italian roundabouts tend to be less safe. Potential reasons for this finding are explored.
Comparison of Safety Performance Models for Urban Roundabouts in Italy and other Countries / Sacchi, Emanuele; Bassani, Marco; Persaud, B.. - In: TRANSPORTATION RESEARCH RECORD. - ISSN 0361-1981. - STAMPA. - 2265:(2011), pp. 253-259. [10.3141/2265-28]
Comparison of Safety Performance Models for Urban Roundabouts in Italy and other Countries
SACCHI, EMANUELE;BASSANI, Marco;
2011
Abstract
In Italy, almost half of all road crashes occur at intersections, mostly in urban areas. However in recent years the widespread conversion of at-grade intersections to roundabouts has brought many advantages in terms of safety. To assess safety benefits of this kind of intersection, transportation professionals need the powerful statistical tool known as the Safety Performance Function (SPF). To date there has been no reported application of this tool to assess the relative safety performance of Italian urban roundabouts. This paper fills that void, thanks to the availability of data sets from two Municipalities in Northern Italy. SPFs were estimated for each city with the negative binomial error distribution and then recalibrated for application in the other city using the procedure being implemented in the Highway Safety Manual. Model reliability and between-city transferability was evaluated with the Cumulative Residuals (CURE) method. To assess how the Italian roundabout safety performance functions might be used to learn lessons from differences in crash experience for similar intersections elsewhere, a comparison with models from other countries is also provided. This comparison revealed that Italian roundabouts tend to be less safe. Potential reasons for this finding are explored.File | Dimensione | Formato | |
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https://hdl.handle.net/11583/2382468
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