Other than passenger 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, stairs and other areas. This is only for travelling in a straight direction. However, it is often overlooked when the ramp is curved; the requirement of 1500mm between handrails becomes the travel path’s minimum width required under the code.
This begs the question: Is there a minimum inner radius that defines a path as a curved ramp and, therefore, requires a 1500mm width? The short answer is no.
Figure 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 ‘crablike’ motion.
The code doesn’t allow for a slightly curved ramp to maintain a 1000mm width between handrails. It also does not allow for linear interpolation of widths (like the spacing of landings on ramps or walkways) between handrails dependent on the inner radius dimension to the curve of the ramp as it does for the length and gradient of ramps between 1:14 and 1:20.
This issue has been prevalent on a few of our recent jobs, 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 strictly requires the width of a curved ramp to be 1500mm between handrails.