Other than passenger lifts and platform lifts, ramps are the essential accessible path of travel for a person in a wheelchair wanting to gain access to and from differing finished floor levels.
AS1428.1:2009 indicates that a minimum dimension of 1000mm is required for the path of travel distance between handrails on ramps and stairs etc. This is only for travelling in a straight direction. However, it is often overlooked where the ramp is curved, the requirement of 1500mm between handrails becomes the minimum width of the path of travel required under code.
The question then gets asked, is there a minimum inner radius that defines it as being a curved ramp, and therefore, requiring a 1500mm width? The short answer is, no.
Fig. 20 of AS1428.1:2009 provides designers with the gradients required to design a curved ramp of differing inner radiuses. The reason a curved ramp with a tighter radius requires a shallower gradient is because of the cross-fall of the ramp. A person in a wheelchair is essentially on a slant manoeuvring themselves around the bend of the ramp. Often referred to as a ‘crab’ like motion.
The code doesn’t allow for a slightly curved ramp to maintain a 1000mm width between handrails. Nor does it allow for linear interpolation of widths (like the spacing of landings on a ramp or walkway) between handrails dependant on the inner radius dimension to the curve of the ramp as it does for the length and gradient of ramps between 1:14 – 1:20.
This issue has been prevalent on a few recent jobs here at MGAC and we are yet to provide an argument as to why the ramp should not have a width of less than 1500mm varying with the gradient of the ramp. At this stage it is clear that AS1428.1:2009 has a strict compliance that the width of a curved ramp is required to be 1500mm between handrails.
John La Scala