Queue lengths and delays at entry points are the important indices for measuring the performance of roundabouts. The object of this study is to find out suitable methods for estimating these indices. Several formulae for estimating average queue length and delay at roundabout entries have been developed. The well-known formulae are those developed by Kimber and Hollis. Field observations on queue lengths and delays at roudabout entries indicate Kimber's formulae provide reasonable predictions for undersaturated traffic conditions. New formulae, based on Kimber's formulae, are derived by introducing two new parameters, one for adjusting the deterministic equation and the other for increasing the approaching speed. The parameters used in this new formulae are determined on the basis of the average simulation data for over-saturated conditions. A computer program was developed to apply the research results in practice. (A)
Samenvatting