01371094

Component

Roundabout capacity analysis in Portugal, as in many other countries, is based on the UK regression method. Due to its empirical nature, this method has some limitations, particularly for studying innovative layouts, which has recently motivated research in Portugal into the use of capacity methods based on gap-acceptance theory. This paper describes the results of a related project: the estimation of critical and follow-up headways at Portuguese roundabouts. For this study, gap-acceptance data was collected at six roundabouts, in two cities, and used to estimate the parameters at each entry, for the left and right entry lanes independently. Several estimation methods were used (Siegloch, Raff, Wu, Maximum Likelihood and Logit). The results reveal important specificities of the methods that have significant effects on the results and therefore on the capacity estimates. The comparison of the estimates with reference values from other countries indicates significant differences, suggesting the existence of relevant driving style differences, which implies that locally calibrated, country-specific, parameters are required for capacity calculations.

This paper was sponsored by TRB committee ANB75T Roundabouts

01362476

12-2032

English

16p

2012

Transportation Research Board 91st Annual Meeting

Digital/other

Figures; References; Tables

Data collection; Gap acceptance; Headways; Logits; Traffic data; Traffic estimation

Portugal

Highways; Operations and Traffic Management; I70: Traffic and Transport; I73: Traffic Control

Transportation Research Board Annual Meeting 2012 Paper #12-2032

TRIS, TRB

Feb 8 2012 5:07PM