While having a level area to use at the top of a ramp when trying to access a building via its doorways seems like a no brainer, situations where the threshold rise is only 1, 2 or even 3 inches are often dealt with using a simple threshold ramp. In the USA the accessibility regulations now require that even for these low rises that there be a level area in front of the doorway of buildings.
It really does make sense that this level area be available regardless of the rise. Trying to manipulate a door and pass through it using a wheelchair is hard enough without having to deal with gravity pushing you back down the slope whether it’s a 30′ modular ramp or a 3 foot threshold ramp.
How to create these level areas are up to the building owner. They can pour concrete and create sloped access to the platform, they can create the platform out of wood and use threshold type ramps to access the platform, or they can purchase a level entry ramping system that is installed over the existing sidewalk or porch.
I’ve put together a short article on these level entry systems at https://mobilitybasics.ca/wheelchair-ramps/entry-ramps for those who would like more information.