TRANSPORT PLANNING AND TRAFFIC ENGINEERING 4TH EDITION. CHAPTER 21: INTRODUCTION TO COMPUTER-AIDED DESIGN OF JUNCTIONS AND HIGHWAYS

The rapid development of computer packages during recent years has transformed the process of designing highways and junctions. It has enabled the investigation of many more design options, and made design calculations much quicker, more reliable, and less laborious. Computer-aided design (CAD) packages make full use of computer graphics facilities, and have several important functions and applications. In the UK, the Transport Research Laboratory (TRL) has developed analytical programs for priority junctions (PICADY), roundabouts (ARCADY), and traffic signals (OSCADY). MOSS is one of the best-known commercial packages for determining the best alignment for a length of road, and it can also handle junction design. It is important to realise the limitations of any design package that is used, and to ensure that all the input information is correct and up to date. The data input requirements for junction design programs and road alignment design packages are listed. Numerical examples are given of the following tables from ARCADY output: (1) queue and delay information for each 15min time segment; (2) effects of marginal design changes on roundabout capacity; and (3) predictions of vehicle and pedestrian accident frequencies. Examples of graphical output from MOSS road alignment designs are also given. For the covering abstract, see IRRD 892228.