A GIS-based Route Mapping Tool for Disabled Access in Urban ...

166signer. Selection is made primarily through a ‘main menu’ that is permanently visible,with further navigation through the system being facilitated by pop-up menus.The model was designed to be a menu driven programme to ensure that users do notrequire any knowledge of ArcView ® or GIS and is usable by those with little computingknowledge. All choices are made using well-spaced ‘buttons’ with each displayinga simple textual description of the option and Microsoft ® accessible toolswere enabled so that users with mobility impairments could navigate the model andinteractive maps using the 'mousekeys' if preferred. All the scripts for the interfaceare contained within the project and upon initiating the GIS-based model all the requireddata are loaded into the main view and the legends are set.MAGUS has been programmed to use the functionality offered by network analysisextension within ArcView. This enables the modelling of spatial networks byproviding tools to determine paths through linear network systems. The model assessesthe accessibility of routes around the urban area by calculating the 'impedance'that each urban barrier, found along a route, poses to wheelchair users. Impedance isthe ‘cost’ expressed in terms of barrier weightings, associated with each street routeor turn. The weightings were determined based upon the perceptions of wheelchairusers and direct measurements e.g. rolling resistance. Impedance values are calculated,within the virtual table, based upon user specifications and selected route option.Any feature upon a route that prevents wheelchair access is assigned a negativeimpedance value, thereby prohibiting route determination. Among the criteria thatare used to start up the route planning procedure is 'type of wheelchair'. Three categoriesof wheelchair are recognised: manual self-propelled, manual assisted andpowered. Furthermore, each user is required to provide an assessment of their relativefitness or capacity to travel, employing a weighting scale of 10 (low level of fitness/poorability to travel) to 100 (high level of fitness/good ability to travel). Thisallows the route to take into account users demands whilst ensuring the system not sodetailed as to make it difficult to use for non-wheelchair users. Two possible methodsof route selection have been incorporated so that a user may select either an optimalroute based on a 'from and to destination(s)’, or all wheelchair accessibleroutes from a specified location. A further number of options are available in routeselection. For example, six types of route can be selected including shortest route,route with the best surfaces, slopes