Kelly, John2008-06-112008-06-112007-07Kelly, J 2007,'Application of robust methods to car ownership trends modelling in Johannesburg', Paper presented to the 26th Annual Southern African Transport Conference, South Africa, 9 - 12 July 2007. 10p.192001702Xhttp://hdl.handle.net/2263/5871This paper was transferred from the original CD ROM created for this conference. The material on the CD ROM was published using Adobe Acrobat technology. The original CD ROM was produced by Document Transformation Technologies Postal Address: PO Box 560 Irene 0062 South Africa. Tel.: +27 12 667 2074 Fax: +27 12 667 2766 E-mail: doctech@doctech.co.za URL: http://www.doctech.co.zaPaper presented at the 26th Annual Southern African Transport Conference 9 - 12 July 2007 "The challenges of implementing policy?", CSIR International Convention Centre, Pretoria, South Africa.ABSTRACT:Robust regression and local polynomial smoothing are applied to the inverse problem for the logistic differential equation (DE) model, in order to develop a more objective, accurate and automatable trends model. A method of inferring the time shift parameter is proposed and applied, allowing the closed form solution of the DE to be used for the prediction of ownership levels in Johannesburg. A simulation study is employed to verify and evaluate the application of non-linear regression to the inverse problem. It is demonstrated that considerable improvements in accuracy, over the transformation to linear-form method, can be obtained. However, on application to actual data, the non-linear regression algorithm fails to converge. The appropriateness of the methods in the case of lower asymptote and early growth phase data, and heterogeneous populations are investigated by simulation.450376 bytesapplication/pdfenUniversity of PretoriaTransport policiesRobust regressionLocal polynomial smoothingTime shift parameterTransportation -- South Africa -- CongressesTransportation services -- South Africa -- CongressesAutomobile ownership -- South Africa -- Johannesburg -- CongressesAotomobile ownership -- South Africa -- Johannesburg -- Mathematical modelsEvent