Guidance System

About The Guidance System. Initially the optical 'self-steering' guidance system was called 'Visée', but when Matra (who developed it) was bought out by Siemens they rebranded the technology as 'Optiguide'. When first introduced 'Visée' was claimed to be the first technology to use Artificial Vision in passenger transport. It works by a forward looking video camera detecting the correct path by 'seeing' the contrast between a 'virtual rail' comprising of twin white dashed lines and the darker road surface on which they are painted (typically normal white traffic paint is used), with the image being analysed by a computer to determine the vehicle's position relative to its expected path and then adjusting the steering as required. There are two options for the virtual rail, with this being located either down the centre of the vehicle or offset to the left. Originally developed to enable accurate docking at bus stops, experience found that it could be equally competent for full-time vehicle guidance, albeit at speeds of up to 40 km/h (about 25mph). When used solely for bus stop docking the 'virtual rail' usually extends 50 metres in each direction before and after the bus stop. The design criteria is for a horizontal gap of 6cm (a little under 2½") between the bus and bus stop platform. Although perhaps intended for 'rubber tyred' tram-like vehicles Optical guidance can be fitted to other types of bus as well - initially most trials used otherwise 'standard' Renault (Irisbus) Agora diesel buses and nowadays some of the other bus designs within the Irisbus family use it too (see below). On the Irisbus stand at the 1999 UITP exhibition in Toronto a short promotional film showed a Renault (Irisbus) Agora bus fitted with optical guidance undergoing trials. Scenes included safe operation in a wide variety of climatic conditions including torrential rain and fog (but not snow), and how easily the driver can safely regain steering control to take emergency action to avoid a potential collision / accident. Interestingly, the film also showed a Civis prototype equipped with O-Bahn / kerb guided bus style guide-wheels while a computer simulation demonstrated it on a mixed mode journey combining both guidance systems. The presence of the raised kerbs would be to help meet safety concerns regarding situations where (for instance) the guidance lines become invisible to the camera - such as in wintry weather conditions - and on slippery roads when safety dictates that all rubber-tyred traffic have to slow down. Originally the raised kerbs and physical guidewheels were stated to only be needed in case the optical guidance system derailed (with there not being any physical contact at other times) but at least one system promoter has suggested using the physical system instead (although many years later this has not come to pass).
Irisbus promotional photograph showing a flat (conventional bus) fronted Cristalis bus on the TEOR route in Rouen.		Scan from Irisbus promotional leaflet showing "hands free" driving.
Agora L on Rouen TEOR line T1 at the "Mont aux Malades" terminus at Mont-Saint-Aignan. Agora buses locate their camera systems at the base of the windscreen just inside the bus. http://commons.wikimedia.org/wiki/File:10-01-08_228_T1_6.JPG.		Citelis 18 on Rouen TEOR line at the "Bizet" terminus at Canteleu. Citelis buses locate their camera systems in a visually distinctive way in a roof mounted pod at the front of the bus. http://commons.wikimedia.org/wiki/File:28-07-08_6108_T3.JPG.