wires installed; even if the entire passenger route is equipped with guidance rails and wires, as in Caen, the depot need not be located immediately by the track, saving planners from having to find space for a new yard in what may be a central and high-valued area of the city. Another advantage over trams, which was particularly of interest to planners in Nancy, is that rubber tyres give significantly more traction than steel wheels, and so can be used to climb steeper hills, up to a grade or slope of 13%. The Nancy route T1 includes a section with a 13% grade. Compared to buses, the use of a guidance rail allows GLT vehicles running in parallel lanes to pass closer together than drivers could safely steer. They can also draw up to level, tram-like platforms that allow for easier boarding, and give access to passengers dependent on wheelchairs without requiring the time-consuming deployment of ramps or 'kneeling' systems. Disadvantages The GLT systems in place have experienced some mechanical problems which, though they have largely been resolved, have discouraged some other cities from adopting the technology. The vehicles have shown a tendency to move erratically when running free, and do not respond well should the driver mistakenly attempt to steer while following the guidance rail (for example, to avoid a pedestrian or animal running into the street). In addition, due to the tyres running over the same spot in the road, in both Nancy and Caen there has been significant rutting of the roadway, resulting in extensive repairs at significant cost to the operator. This could be considered to add to the already high running costs. Ride quality is also said to be poor, not much of an improvement on a bus, due to the four-wheeled design, whereas trams have bogies. Guidewheel mechanical failures have occurred, causing the trolleybus to swerve off the roadway. This is due to the high centrifugal forces exerted on the wheel when rounding corners. Due to this, a speed limit of is now enforced on corners. One of the main aims of the system, to achieve a lower cost per kilometre than trams, has failed. Other French tramways achieve a cost per kilometre at least 10% lower than that for the guided bus. Similarly, the cost per person of the vehicles is also noticeably higher with the guided bus than a tram. Where snowfall