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To cite this version:Tone Lerher, Matjaz Sraml, Iztok Potrc, Tomaz Tollazzi. Travel time models for double-deep automated storage and retrieval systems. International Journal of Production Research, Taylor & Francis, 2010, 48 (11) Abstract:In this paper new analytical travel time models for the computation of cycle times for unit-load double-deep automated storage and retrieval systems (in continuation double-deep AS/RS) are presented. The proposed models consider the real operating characteristics of the storage and retrieval machine and the condition of rearranging blocking loads to the nearest free storage location during the retrieval process. With the assumption of the uniform distributed storage rack positions and the probability theory, the expressions of the single and modified dual command cycle have been determined. The proposed models enable the calculation of the mean cycle time for single and dual command cycles, from which the performance of the double-deep AS/RS can be evaluated. A simulation model of the selected double-deep AS/RS has been developed to compare the performances of the proposed analytical travel time models. The numerical analyses show that with regard to the examined type of double-deep AS/RS with a different fill-grade factor, the results of proposed analytical travel time models correlate with the results of simulation models of double-deep AS/RS.

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Alternative types of roundabouts are usually more recent and have been implemented only in certain countries. Typically, they differ from "standard" roundabouts in one or more design elements, whilst the purposes of their implementations are also specific. The main reasons for their implementations are particular the disadvantages of "standard" one-or two-lane roundabouts in particular circumstances or changes of "actual circumstances" which in the past has led to roundabout implementations. Today, several different types of roundabouts are well-known ("mini", "double mini", "dumbbell", "with transition central island", "with joint splitter islands", "traffic signal controlled", "assembled roundabouts" …), and it is possible to stipulate that they will be further developed in the future. This paper illustrates two relative new alternative types of roundabouts-"turbo" and "flower" roundabouts and their comparison from design, traffic safety and capacity point of view.

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